Thomas C. Mort
Andrea Gabrielli
Timothy J. Coons
Elizabeth Cordes Behringer
A. Joseph Layon
Immediate Concerns
Major Problems
Maintenance of the airway must be one of the most essential goals of critical care. Critical care personnel apply their expertise in resuscitating the critically ill patient by volume infusion, invasive line placement, titration of vasoactive medications, analysis of laboratory studies, and performing radiographic examinations, but may neglect the “A” of the ABCs until further clinical deterioration turns the need for airway management into an emergency. Airway functions are numerous and, though it primarily supports the exchange of oxygen and carbon dioxide, the airway assists in the regulation of temperature, contributes to the warming and humidification of inspired gas, traps and expels foreign particles, and protects against foreign body entry into the lungs through a complex array of reflex responses.
Many of these functions are altered or lost in critically ill patients. Airway obstruction can result from infection, trauma, laryngospasm, soft tissue edema, and aspiration of gastric or other noxious materials. Protective reflexes may be lost as a result of disease and depression with narcotics, sedatives, or paralytic agents. Humidification can also be lost as various appliances that bypass the nose, pharynx, and upper airway are inserted to maintain airway patency. Clinicians must then employ methods to maintain airway hydration, including humidifiers, nebulizers, and heat–moisture exchangers. These devices introduce additional problems such as nosocomial infections and increased work of breathing.
General Principles
Primum non nocere (first do no harm) applies most fittingly to the airways of critically ill patients. The intensivist must not only be knowledgeable of respiratory pathophysiology, but also must possess technical skill and sound judgment in airway management. Various options are available, including bag-valve-mask ventilation, translaryngeal intubation (oral or nasal), tracheotomy, and cricothyroidotomy. Adjunctive drugs such as local anesthetics, narcotics, benzodiazepines, barbiturates, muscle relaxants, ketamine, and propofol play an important role. Their use facilitates airway control and improves respiratory support.
In most instances, bag-valve-mask (Fig. 38.1) ventilation precedes tracheal intubation. Immediate correction of hypoxemia should be attempted by application of a mask and initiation of bag ventilation with an increased FiO2 while equipment for intubation is prepared. An appropriate mask provides a tight seal around the nose and mouth, and the colorless plastic with soft and pliable edges allows visualization of the mouth and secretions. The mask is attached to the resuscitation (self-inflating or collapsible) bag with a high-flow oxygen source. Various systems will supply an FiO2 between 0.60 and 1.0, depending upon the mask fit, the manufacturer, the oxygen flow rate, and the style of bag design based on the Mapleson (Fig. 38.2) designation (1,2,3). Proper inflation requires two hands: One to hold the mask firmly in place against the patient's face, and the other to compress the bag (4). The mandible must be lifted to create a seal without airway occlusion. An oropharyngeal or nasal airway facilitates oxygen delivery by bypassing or retracting the tongue (5,6). Forceful bag compression should be avoided to prevent gastric distention and possible pulmonary aspiration. Gentle insufflation allows clinical assessment of lung compliance and minimizes complications. Contraindications to bag-valve-mask ventilation include airway obstruction, pooling of blood or secretions in the pharynx, and severe facial trauma (7,8).
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Figure 38.1. Standard bag-valve-mask setup. Note that the bag is self-inflating, so it can be used with (usual) or without (in emergencies) an external gas supply. The “tail” of the bag serves as an oxygen reservoir. |
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Figure 38.2. A Mapleson D bag. Note that this is not a self-inflating bag, and hence must be used with an external gas source. The positioning of the fresh gas inlet—designating the Mapleson bag class—and the fresh gas flow impact the amount of rebreathing. It is possible, in an inadvertent situation, if the fresh gas runs out and the pressure regulating (“pop off”) valve is closed, to continuously rebreathe exhaled gas. This would ultimately result in injury or death. |
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Table 38.1 Indications for tracheal intubation |
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Critically ill patients require tracheal intubation (Table 38.1) for several reasons (7). When inadequate ventilation is observed, tracheal intubation becomes necessary. It provides airway patency, facilitates tracheobronchial suctioning, and minimizes aspiration of blood, gastric contents, or secretions into the pulmonary tree. Oxygen administration and mechanical ventilation correct hypoxemia and hypercapnia, improve the alveolar-to-arterial oxygen partial pressure gradient, and reduce intrapulmonary shunting. In emergency situations in which intravascular access is absent, drug administration into the endotracheal tube can be life saving. Epinephrine, atropine, lidocaine, and naloxone exert their pharmacologic effects after tracheal administration (9,10,11,12).
Relative or absolute contraindications to conventional tracheal intubation exist in patients with traumatic or severe degenerative disorders of the cervical spine; in those with acute infectious processes such as acute supraglottitis or intrapharyngeal abscess; and in patients with extensive facial injury and basal skull fracture (13,14,15). Blind nasal intubation may be contraindicated in upper airway foreign body obstruction because the tube may push the foreign body distally and exacerbate airway compromise (13,14,15,16).
Anatomic Considerations
Adult
Specific anatomic characteristics may determine the ease or difficulty of intubation. The intensivist sometimes does not have the flexibility to examine and assess the airway at leisure but must act quickly with skill and confidence. A good working knowledge of the anatomy of the mouth, neck, cervical spine, and pulmonary tree is mandatory for a successful and safe intubation. Examination of cervical spine mobility includes flexion and extension. Neck flexion aligns the pharyngeal and tracheal axes, whereas head extension on the neck and opening of the mouth align the oral passage with the pharyngeal and tracheal axes. This maneuver places the patient in a “sniffing position” (17) (Fig. 38.3). Incorrect positioning of the head and neck accounts for one of the common errors in orotracheal intubation. Flexion and extension of the head decreases 20% by 75 years of age. Degenerative arthritis limitscervical spine motion, more so with extension than flexion. Movement of the spine is contraindicated in the presence of potential cervical spine injury; hence, patients are maintained in a neutral position with in-line stabilization. Barring the edentulous patient, the front component of the hard cervical collar is commonly removed to allow full mandibular movement and optimize mouth opening. This maneuver removes the standard flexion and extension movements used to optimize the line of sight and therefore reduces one's ability to see “around the corner” in many cases (18,19,20,21,22). Each technique, maneuver, or accessory airway device available may alter the alignment of the cervical spine to a small degree based on the device itself, combined with the force and maneuvering performed by the operator, despite in-line stabilization (18,23,24,25). The available data and accumulated clinical experience do not dictate one method over another, especially when many practitioners who suggest an awake fiberoptic intubation is the “best” approach may themselves have reservations and concerns regarding their own comfort and competency at performing such a technique (18,26,27). The most appropriate technique is debatable but it would be prudent that the practitioner do his or her best with familiar equipment and approaches. This would not be the time to attempt to use a newly purchased item (e.g., rigid fiberscope), since one has not become competent and familiar with its use on a manikin and elective “easy” patients. Other diseases may place the patient at risk for atlantoaxial and cervical spine instability, and reduced mouth opening beyond those with known or suspected neck pathology (28).
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Figure 38.3. Demonstration of the “sniffing position” for optimal visualization of the glottic opening. |
Important anatomic landmarks may help the physician during direct laryngoscopy (Fig. 38.4). The cricoid, a circle of cartilage above the first tracheal ring, can be compressed to occlude the esophagus (Sellick maneuver), thereby preventing passive gastric regurgitation into the trachea during intubation (29). The epiglottis, a large cartilaginous structure, lies in the anterior pharynx. The vallecula, a furrow between the epiglottis and base of the tongue, is the placement site for the tip of a curved laryngoscope blade. The larynx is located anterior and superior to the trachea and contains the vocal cords.
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Figure 38.4. Laryngoscopic landmarks. Panel shows the cricoid cartilage. |
Pediatric
Several anatomic differences exist between the adult and the pediatric airways. Pediatric patients have a relatively large head and flexible neck. The air passages are small, the tongue is large, the epiglottis is floppy, and the glottis is typically slanted at a 40- to 50-degree angle, making intubation more difficult. Mucous membranes are softer, looser, and more fragile, and readily become edematous when an oversized endotracheal tube is used.
Adenoids and tonsils in a child are relatively larger than those in the adult. The epiglottis and larynx of infants lie more cephalad and anterior, and the cricoid cartilage ring is the narrowest portion of the upper airway. In contrast, the adult glottic opening is narrowest. Additionally, the pediatric vocal cords have a shorter distance from the carina, with the mainstem bronchus angulating symmetrically at the level of the carina at about 55 degrees. In adults, the right mainstem angulates at about 25 degrees and the left at about 45 degrees. The cupulae of the lungs are higher in the infant's neck, increasing the risk of lung trauma.
To avoid delay and minimize complications, all anticipated equipment and drugs must be available for the planned intubation technique (Table 38.2, Fig. 38.5). Additionally, a difficult airway cart or bag with a variety of airway rescue devices—as well as a bronchoscope and/or fiberoptic laryngoscope—should be readily available (30,31). It is far better to have a limited assortment of airway devices with which personnel are familiar and competent to handle than to have an expensive, well-stocked cart containing a plethora of devices that the airway personnel have not practiced with nor have gained competence.
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Table 38.2 Standard equipment and drugs for translaryngeal intubation |
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Figure 38.5. Demonstration of the equipment and drugs that must be available for the planned intubation technique. |
Medications
The pharynx, larynx, and trachea contain a rich network of sensory innervation, necessitating the use of anesthesia, analgesia, sedation, and sometimes muscular paralysis during intubation of a spontaneously breathing, awake, or semiconscious patient. Drugs commonly used are local anesthetics, sedative-hypnotics (sodium thiopental, propofol, etomidate), narcotics (fentanyl, morphine sulfate, hydromorphone, remifentanil), sedative-anxiolytics (benzodiazepine class—midazolam), muscle relaxants (depolarizing and nondepolarizing agents), and miscellaneous agents such as ketamine and dexmedetomidine.
Local Anesthetics
The use of local anesthetics is often overlooked in the intensive care unit (ICU) setting for a number of reasons: (a) it is far easier to administer an intravenous agent than to take the time to prepare the patient with topical anesthetics or local nerve blocks; (b) the urgency of the situation may preclude their timely use; (c) the patient's anatomic/physical characteristics may limit their effective application (poor or nonexistent landmarks, coagulopathy, excessively dry mucosa, excessive secretions, patient uncooperation); and (d) the underappreciation of their value in managing the airway and the underestimation of airway difficulty in the ICU setting. Moreover, access to the proper local anesthetic agents and the accessories for their accurate delivery (nebulizer, atomizer, Krause forceps, cotton balls, Abraham laryngeal cannula, etc.) may be limited in the ICU setting unless they have been prepared and gathered in advance (difficult airway cart).
Aerosolized or nebulized 1% to 4% lidocaine can readily achieve nasopharyngeal and oropharyngeal anesthesia if the patient is cooperative and capable of deep inhalation, thus limiting its usefulness in the ICU. The author has found this method less desirable due to its time-consuming application process and its limited effectiveness when compared to topically applied local anesthetics or local blocks. Transtracheal (cricothyroid membrane) instillation of 2 to 4 mL of 1% to 4% lidocaine with a 22- to 25-gauge needle causes sufficient coughing-induced reflex to afford ample distribution to anesthetize the subglottic and supraglottic regions plus the posterior pharynx in 90% of patients (32,33,34). Cocaine provides excellent conditions for facilitating intubation through the nasopharynx due to its outstanding topical anesthetic and mucosal and vascular shrinkage capabilities (33). However, in-hospital availability may limit its use in favor of phenylephrine or oxymetazoline combined with readily available local anesthetics. Lidocaine ointment applied to the base of the tongue with a tongue blade or similar device allows performance of direct laryngoscopy in many patients. If time permits, nasal spraying with a vasoconstrictor followed by passing a progressively larger nasal airway trumpet from 24 French to 32 French that is coated/lubricated with lidocaine gel/ointment provides exceptional coverage of the nasocavity in preparing for a nasal intubation. Instillation of liquid lidocaine via the in situ nasal trumpet offers an excellent conduit to distribute additional topical anesthetic to the orohypopharynx. It is best performed in the sitting-up position to enhance coverage of the airway structures.
Barbiturates
Sodium thiopental, an ultra-short-acting barbiturate, decreases the level of consciousness and provides amnesia without analgesia after an intubation dose of 4 to 7 mg/kg ideal body weight (IBW) dose over 20 to 50 seconds (administered via a peripheral IV) in the otherwise healthy patient. Its short duration of action (5–10 minutes) makes it ideal for short procedures such as intubation. Thiopental has an excellent cerebral metabolic profile in regards to lowering cerebral metabolic rate while maintaining cerebral blood flow as long as systemic blood pressure is maintained within an adequate range. However, thiopental may lead to hypotension in critically ill patients due to its vasodilatation properties, especially in the face of hypovolemia (34). Though inexpensive, its use in the operating room has declined in favor of propofol. Unfortunately, many upcoming personnel do not develop a working knowledge of the barbiturates. In the ICU setting, reducing the dose of thiopental to 1 to 2 mg/kg IBW is very useful for preparing the patient for tracheal intubation with or without a muscle relaxant.
Narcotics
Narcotics such as morphine, hydromorphone, fentanyl, and remifentanil reduce pain perception and allay anxiety, making intubation less stressful. In addition, they have some sedative effect, suppress cough, and relieve dyspnea (35,36). Fentanyl and the ultra-short-acting remifentanil have a more rapid onset and shorter duration of action than the conventional narcotics used in the ICU setting for analgesia (37,38,39). Morphine may lead to histamine release and its potential sequelae. Though all narcotics cause respiratory depression, the newer synthetic narcotics may lead to muscular chest wall rigidity that may hamper ventilation and may contribute to episodes of bradycardia. Narcotics, titrated to effect, are quite effective in settling the patient undergoing an awake intubation. Their analgesic, antitussive, and antihypertensive qualities are extremely valuable especially in light of the ability to rapidly reverse excessive narcotization.
Benzodiazepines
Benzodiazepines such as lorazepam and midazolam have excellent amnestic and sedative properties (40). Diazepam has seen its use decline markedly due to its less favorable distribution and clearance characteristics. This drug class does not provide analgesia and may be combined with an analgesic agent during intubation, especially if an awake or semiconscious state with maintenance of spontaneous ventilation is the goal. Midazolam largely has replaced diazepam for intubation because of its more rapid onset and shorter duration of action. Lorazepam use for intubation is possible, but it is hampered by a slower pharmacodynamic onset (2–6 minutes) as compared to midazolam. Hypotension may occur in hypovolemic patients, and benzodiazepines potentiate narcotic-induced respiratory depression.
Muscle Relaxants
The clinician may desire or need to administer a muscle relaxant to optimize intubation conditions, but the vast majority of ICU intubations may be accomplished without such agents. There are basically two perspectives regarding the use of muscle relaxants in the critically ill patient:
1. The administration of a sedative-hypnotic agent with a rapid-acting muscle relaxant, typically succinylcholine, as the standard technique for tracheal intubation is often cited as improving intubation conditions and leading to fewer complications (41). Though this recommendation has much merit, the ubiquitous acceptance of this approach has fallen into the hands of practitioners who frequently do not fully contemplate the patient's risk for airway management difficulties and may not have access or a good working knowledge of airway rescue devices to bail them out if conventional laryngoscopy techniques fail (42,43,44,45,46). Many who use this approach may do so regardless of their patient assessment. This is akin to a “shoot first, ask questions later” approach. One may expect outcomes with this approach akin to those noted when it is used in social situations.
2. The alternative approach is to assess the patient's airway-related risk factors, the patent's potential needs, and the patient's ability to tolerate methods of preparation (e.g., topical, light sedation, and then proceed with induction) followed by customization of the preparation of the patient rather than a “one size fits all” mentality. Though the decision for their use is the clinician's to make, one must be a patient advocate since he or she rarely ever has any say in the matter. It is our opinion that any clinician who administers drugs such as induction agents, including paralytics, thus rendering the patient entirely dependent on the airway management team, must have developed a rescue strategy coupled with the equipment to deploy such a strategy (43,45,46).
The indications for muscle relaxants include agitation or lack of cooperation not related to inadequate or no sedation, increased muscle tone (seizures, tetanus, and neurologic diseases), avoidance of intracranial hypertension, limiting patient movement (potential cervical spine injury), and the need for shortening the time frame from an awake state with protective reflexes to an asleep state with the goal of rapid tracheal intubation (upper gastrointestinal bleed).
Neuromuscular blocking agents may cause depolarization of the motor end-plate (succinylcholine, a depolarizing agent) or prevent depolarization (nondepolarizer: pancuronium, vecuronium, rocuronium). Succinylcholine has a rapid onset and short duration of effect, making it useful in the critical care setting; however, it may raise serum potassium levels by 0.5 to 1.0 mEq/L. It is contraindicated in bedridden patients and in those with pre-existing hyperkalemia, burns, or recent or long-term neurologic deficits (47,48,49). Other side effects are elevation of intragastric and intraocular pressures, muscle fasciculation, myalgia, malignant hyperthermia, cardiac bradyarrhythmias, and myoglobinuria. Depending on the initial dose—our recommendation is 0.25 mg/kg IBW—and systemic conditions, succinylcholine has a relatively short duration of 3 to 10 minutes. However, if airway management difficulties exist, one should never presume the muscle relaxant will wear off in time to “save” the patient and allow spontaneous patient-initiated ventilation. Emergency rescue techniques should be deployed as early as possible when conventional intubation methods prove unsuccessful.
Nondepolarizing muscle relaxants have a longer time to onset and duration of action as compared to succinylcholine. Rocuronium (typical operating room dose, 0.6 mg/kg) can approach succinylcholine in rapid time of onset if dosed accordingly (1.2 mg/kg), but the increased dosage requirements to meet this objective come with some cost: extended duration of drug action and increased cost.
One controversy to consider when faced with a known or suspected difficult airway: If the practitioner is contemplating the use of a muscle relaxant, which agent is most advantageous? Standard dosing of succinylcholine potentially offers the awake option earlier than a nondepolarizing agent, but if it wears off too soon, then a period of poor or marginal ventilation may hamper patient care and require a transition to a rescue option. Conversely, a short-acting nondepolarizer offers good transition to a rescue plan if mask ventilation is adequate, but does not allow an early-awaken option (46).
Ketamine
Ketamine, a phencyclidine derivative, provides profound analgesia, amnesia, and dissociative anesthesia (50,51). The patient may appear awake but is uncommunicative. Airway reflexes are often, but not always, preserved. Ketamine has a rapid onset and relatively short duration of action. Its profile is unique: it is a myocardial depressant, but this is often countered by its sympathomimetic properties, thus leading to hypertension and tachycardia in many patients. Its use in the critically ill patient with ongoing activation of his or her sympathetic outflow could lead to profound hemodynamic instability since the underlying myocardial depression may not be successfully countered. Though it offers favorable bronchodilatory properties, it promotes bronchorrhea, salivation, and a high incidence of dreams, hallucinations, and emergence delirium (50,51).
Propofol
Propofol also is useful during intubation, especially if titrated to the desired effect rather than simply administering a one-time bolus (52,53,54,55). After intravenous administration via a peripheral IV (1–3 mg/kg IBW), unconsciousness occurs within 30 to 60 seconds. Awakening is observed in 4 to 6 minutes with a lower lingering level of sedation compared to other induction agents (52,53,55). Side effects include pain on injection, involuntary muscle movement, coughing, and hiccups. Hypotension, cardiovascular collapse, and, rarely, bradycardia may complicate its use, especially if administered in rapid single-bolus dosing in the critically ill patient with relative or absolute hypovolemia, a systemic capillary leak syndrome, or pre-existing vasodilatation (e.g., sepsis, systemic inflammatory response syndrome [SIRS]). It, however, is an excellent agent that may be titrated to a desired effect while maintaining spontaneous ventilation.
Etomidate
Etomidate is considered by many to be the preferred induction agent in the critically ill patient due to its favorable hemodynamic profile, as compared to the other available induction agents. The hemodynamic stabilization offered by etomidate, however, should not be considered a panacea since it too may lead to hemodynamic deterioration (56,57). Currently, its role as a single-dose induction agent is in question due to its transient depression of the adrenal axis. Once regarded as a minor concern, this adrenal suppression may be much more influential in the outcome of the critically ill. Some have expressed caution with etomidate's use as a single-dose induction agent, especially in the septic or trauma populations. A variety of opinions exist, ranging from an opinion that etomidate should be avoided completely, to its avoidance in select populations such as the septic population, to its use—if at all—with empiric steroid replacement therapy for at least 24 hours (58,59,60). Perhaps well-designed clinical trials should be performed to determine the relevance of these published precautions. Until more information is available, the practitioner who chooses to use etomidate would be wise and prudent to consider communicating with the ICU care team so they are aware of its use and may act accordingly if hemodynamic instability occurs within 24 hours of administration.
Dexmedetomidine
Dexmedetomidine is an ultra-short-acting α2 agonist that, when administered intravenously, provides analgesia and mild to moderate sedation with relatively minimal respiratory depression while affording tolerance of “awake” fiberoptic and conventional tracheal intubation (61,62). While a most useful drug, its cost prevents its use in many centers.
Equipment for Accessing the Airway
Esophageal Tracheal Combitube
The esophagotracheal airway (Combitube, ETC) (Fig. 38.6), recommended by the American Heart Association (AHA) Advanced Cardiovascular Life Support (ACLS) course and other national guidelines (30,63,64), is an advanced variant of the older esophageal obturator airway and the pharyngeal tracheal lumen airway (PTLA). The double lumens with proximal and distal cuffs allow ventilation and oxygenation in a majority of nonawake patients whether placed in the esophagus (95% of all insertions) or the trachea (65,66). Its proximal cuff is placed between the base of the tongue and the hard palate and the distal cuff within the trachea or upper esophagus (67,68). The ETC is inserted blindly, assisted by a jaw thrust or laryngoscopic assistance. Its role in emergency airway management is well recognized and though less popular than the laryngeal mask airway (LMA) or fiberoptic bronchoscope, it may serve a vital role in offering airway rescue when laryngoscopy, bougie insertion, or LMA-assisted ventilation/intubation fails (69). A recent latex-free modification of the Combitube, the Easytuber (Teleflex Ruesch; www.teleflexmedical.com) has a shorter and thinner pharyngeal section, which allows the passage of a fiberscope via an opening of the pharyngeal lumen to inspect the trachea while ventilating.
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Figure 38.6. The esophagotracheal double-lumen airway, the Combitube. |
Tracheal Intubation
When the decision has been made to provide mechanical ventilatory support or airway control, the second question to answer is the route of tracheal intubation: oral versus nasal (unless a surgical airway is clinically indicated). Most commonly, orotracheal intubation is the preferred procedure to establish an airway because it usually can be performed more rapidly, offers a direct view of the glottis, has fewer bleeding complications, avoids nasal necrosis and sinus infection, and allows a larger tracheal tube to be placed as compared to the nasal approach. Finally, the blind nasal approach is particularly benefited by spontaneous ventilation. Airway vigilance should be a goal of the critical care practitioner; thus, conventional and advanced airway rescue equipment must be immediately available during any attempts at airway management. Before attempting to intubate, all anticipated equipment and drugs must be prepared. This may best be provided by an organized “intubation box” containing conventional intubation equipment, with a selection of lubricants, local/topical anesthetics, intravenous induction agents, and medications to assist in treating peri-intubation hemodynamic alterations (heart rate, blood pressure). The box should have a visible lock with hand-breakable deterrent devices to reduce the problem of “missing” equipment. The wide spectrum of patient preparation for tracheal intubation ranges from an unconscious and paralyzed patient, to preparation with mild to moderate dosing of sedatives and analgesics, to the other extreme of topical anesthetics or no medication at all.
Critically ill patients often require only a fraction of the drug doses provided to their elective operating room counterparts. Careful intravenous titration may attenuate hemodynamic alterations, loss of consciousness, apnea, and aspiration. Controversy lies in whether or not to preserve spontaneous ventilation: In essence, should one administer pharmacologic paralyzing agents to the critically ill patient, thus placing the patient in a state in which the practitioner is solely responsible for ventilation, oxygenation, and tracheal intubation? Advocates for paralysis, the majority of which practice in the emergency department locale, cite a low rate of complications and ease of intubation. Conversely, critical care databases suggest that emergency tracheal intubation is far from “safe” and devoid of complications whether or not paralyzing agents are administered (41,43,44,45,70). From a patient advocate standpoint, any practitioner who ablates the patient's ability to spontaneously ventilate via neuromuscular blocking agents must be properly trained and experienced in basic and advanced airway management so that the depth of his or her ability to provide airway control lies well beyond simply conventional laryngoscopy and intubation (45).
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Figure 38.7. Examples of fiberoptic laryngoscope handle and blades, in which the bulb is in the handle and the light is transmitted through fiberoptic bundles. |
Equipment
Laryngoscopes
A laryngoscope (Fig. 38.7) (fiberoptic vs. conventional) is used to expose the glottis to facilitate passage of the tracheal tube. Unfortunately, proper skill and experience using this standard airway management technique varies widely among critical care practitioners. The utility of the laryngoscope under elective circumstances, with otherwise healthy surgical patients, is essentially limited to individuals with a grade I or II view that can be easily intubated (22). Though a difficult view is mentioned by many as being uncommon (22), Kaplan et al. (71) documented a 14% incidence of grade III or IV views despite optimizing maneuvers such as the optimal external laryngeal manipulation (OELM) and the backward upward right pressure (BURP) technique (Fig. 38.8). This is further complicated, as up to 33% of critically ill patients have a limited view with laryngoscopy (epiglottis only or no view at all) (44,45,72). This is why the critical care practitioner responsible for airway management must be prepared to embark on a Plan B or Plan C immediately if conventional direct laryngoscopy fails to offer a reasonable glottic view that allows timely and accurate intubation.
Blades
Laryngoscope blades are of two principal kinds, curved and straight, varying in size for use in infants, children, or adults (Fig. 38.9). Many varieties of both the curved and straight blades have been redesigned in the hopes of augmenting visualization to facilitate passage of an endotracheal tube. Innovations to improve laryngeal exposure include a hinged blade tip to augment epiglottic lifting during laryngoscopy (73), rigid fiberscopes, and video-assisted laryngoscopy (74,75,76,77,78,79,80). These innovations may, depending on the individual patient airway characteristics, offer an improved view of the glottis to improve the first-pass success rate, reduce intubation attempts, potentially reduce the time to intubation in the difficult airway, and potentially result in a reduction in esophageal intubation and other airway-related complications that are relatively commonplace with standard techniques. The future lies with visualizing “around the corner” in the hopes of improving patient airway safety (74,75,76,77,78,79,80).
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Figure 38.8. Diagrammatic representation of the optimal external laryngeal movement (OELM) and backward upward rightward pressure (BURP) maneuvers for optimal visualization of the glottis. |
Endotracheal Tubes
Most endotracheal tubes (ETs) are disposable and are made of clear, pliable polyvinylchloride, with little tendency to kink until they attain body temperature. Though the ETs mold to the contour of the upper airway and present a smooth interior, affording easy passage of suction catheters or a flexible bronchoscope, they may become encrusted with secretions, biofilm, and concretions that may decrease luminal patency and endanger patient care.
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Figure 38.9. Various types of laryngoscope blades in common use. |
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Figure 38.10. The Malinkrodt Hi-Lo Evacuation tube. While it comes in various sizes, it is not optimal for all patients. There is level 1 evidence that, with proper use, it decreases risk of ventilator-associated pneumonia. (From American Thoracic Society. Guidelines for the management of adults with hospital-acquired, ventilator-associated and healthcare-associated pneumonia. Am J Respir Crit Care Med. 2005;171:388–416.) |
In adults, all commonly used ETs are of the cuffed variety, and many now used are types that allow suctioning of subglottic secretions—the Hi-Lo Evacuation ET (Fig. 38.10). The ET cuff ensures a closed system, permitting control of ventilation and reducing the possibility of silent or active aspiration of oronasal secretions, vomitus, or blood, although microaspiration is well recognized. Commonly, ET cuffs are the high volume–low pressure models that offer a broad contact with the tracheal wall and potentially limit ischemic damage to the mucosa. The tube size used depends upon the size of the patient (Table 38.3).
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Table 38.3 Recommended sizes for endotracheal tubes |
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The primary reasons for tracheal intubation will vary from patient to patient and by practitioner, related to not only the patient's pathophysiology, but also the physician's judgment and experience in caring for the critically ill. The main goals of tracheal intubation include protecting the airway from contamination, providing positive-pressure ventilation, providing a patent airway, and permitting access to the tracheobronchial tree for suctioning, instillation of medications, or diagnostic/therapeutic bronchoscopy. While the vast majority of tracheal intubations are via the oral route, the choice between the oral and the nasal—or the transcricoid/transtracheal route—will again be primarily determined by the patient's physical and airway conditions, the expected duration of mechanical support, and the judgment and skills of the practitioner.
Malleable Stylet
A well-lubricated malleable stylet (Fig. 38.11) is preferred by many to preform the ET into a shape that may expedite passing through the glottis. The stylet should be viewed as a guide, not a “spear,” and its tip should be safely inside the ET, never distal to the ET tip (81,82). It should not be used to force the ET into the airway or ram its way through the vocal cords when they are closed or otherwise inaccessible. Also, the popular “hockey stick”–shaped tip used by many is useful, yet its angle must be appreciated by the operator. The angle often will impede advancement into the airway since the ET tip may impinge on the anterior tracheal wall and the sharp angulations of the stylet may impede its own removal from the ET (81,82,83). Ideally, the styleted ET tip should be placed at the entrance of the glottis, and then, with stylet removal, the ET will advance into the trachea less traumatically. Unfortunately, many practitioners unknowingly advance the styleted ET deep into the trachea without appreciating the potential damage the stylet-stiffened ET tip may cause to the tracheal wall.
How Might the Airway Be Accessed?
General Indications and Contraindications
The oral approach is the standard method for tracheal intubation today. The indications are numerous and it may be best to focus on the contraindications. The oral route would not be a reasonable choice when there is limited access to the oral cavity due to trauma, edema, or anatomic difficulties. These contraindications for the oral route would presume that the nasal approach is feasible from both the patient's and clinician's standpoint. If not, a surgical approach via the cricothyroid membrane or a formal tracheostomy would be clinically indicated. Though nasal intubations were a mainstay in earlier decades, the oral approach has displaced it due to the popularity of the “rapid sequence intubation” and the better appreciation of the potential detriments of long-term nasal intubation.
Orotracheal Intubation
The airway care team members should expediently prepare both the patient and the equipment for the airway management procedure. While bag ventilation (preoxygenation) is being provided, obtaining appropriate towels for optimizing head and neck position or blankets for ramping the obese patient and adjusting the bed height and angulation should be carried out (Fig. 38.12, left panel); how not to position is noted in the right panel of Figure 38.12. Assembling the necessary equipment, such as the ET, syringes, suction equipment, lubricant, CO2 detector, and a stylet if desired, should be quickly carried out for the primary airway manager. During this time, a rapid medical-surgical history is obtained, the review of previous intubation procedures sought, and an airway examination completed (30,42). Intravenous access is ensured and a primary plan for induction developed. Access to airway rescue devices should be addressed and, of course, it is best if they are at the bedside. Clear communication among team members is imperative as well as discussion of the plan with the patient, if appropriate. Chaos is to be avoided and, in this context, the individual managing the procedure must insist that unnecessary talking and agitation be limited.
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Figure 38.11. Malleable stylet for use with insertion of an endotracheal tube. |
A tube of appropriate diameter and length should be selected and, though gender is an important factor in size selection, patient height is equally important as there is a linear relationship between the latter and glottic size. Typically, the choice in a woman would be a 7.0 to 8.0 mm ET, and in males an 8 to 9 mm ET would be used. Nonetheless, smaller-diameter ETs should be readily available for any eventuality. A team member should examine the ET for patency and cuff integrity. The 15-mm proximal adapter should fit snugly and the ET kept in its sterile wrapper and not handled until insertion. It may be placed in warm water to soften the PVC tubing, which may assist with passing the ET over a stylet, a tracheal introducing catheter (bougie), or a fiberscope, or during an ET exchange.
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Figure 38.12. Ramping of an obese patient's torso to improve glottic visualization is noted on the left panel. The right panel shows the patient position without proper ramping. |
Based on the patient history and physical examination, combined with the practitioner's judgment, past experience, available equipment, and the needs of the patient, a determination is made as to what induction method is best. Patient preparation for tracheal intubation may range from little to no medication to the other extreme of unconsciousness with muscle relaxation (41,84,85). Considering the earlier discussion involving airway risk assessment, the practitioner will need to determine if preservation of spontaneous ventilation is in the patient's best interest, as well as the depths of amnesia, hypnosis, and analgesia the patient may require so that airway manipulation is tolerated (30,63,64). Titration of a sedative-hypnotic or analgesic to render the patient tolerant of airway manipulation is often based on the practitioner's knowledge and experience of the available induction agents, combined with the perceived needs of the patient plus the predicted tolerance of their administration. The pharmacodynamic effects following administration via an IV site will depend on the IV location (central vs. peripheral, hand vs. antecubital fossa), vein patency, catheter diameter and length, IV flow rate, and the patient's cardiac output.
Central IV access may speed administration and time to onset plus potentially deliver a more concentrated medication bolus as compared to an equal dose administered through an IV on the dorsum of the hand.
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Figure 38.13. Equipment used to topicalize the airway prior to instrumentation: Tongue blade with lidocaine jelly, nebulizer with 4% lidocaine, and nasal dilators of various sizes. |
The practitioner has several choices for patient preparation: (a) awake with no medication; (b) awake with topical anesthesia or local nerve blocks, and with or without light sedation; (c) sedation/analgesia only with the option of neuromuscular blocker use; and (d) a set induction regimen for a rapid sequence intubation (e.g., etomidate and succinylcholine) (41,77,84,85). Faced with a variety of preparation choices and a wide breadth of patient circumstances, the critical care physician will need to decide what approach to pursue based on the medical, surgical, and airway situation; the patient's needs and level of tolerance, balanced by the practitioner's judgment; and access to and experience with airway equipment (41,44,45,84,85).
Awake Intubation
Awake intubation techniques comprise both nasal and oral routes and, most often, involve topically applied local anesthetics (Fig. 38.13) or local nerve blocks. Conversely, if the patient's mental status and response to oropharyngeal stimulation are depressed, no medication may be needed to accomplish intubation. The application of topical anesthesia and a local nerve block requires more time and effort, expanded access to such agents and equipment, more patience, and finesse combined with a broader familiarity of head and neck anatomy (24,86). If done properly, the patient's airway may be managed with nearly all conventional and accessory devices with the exception of the Combitube. Practitioners may prefer to maintain spontaneous ventilation during emergency airway management by avoiding excessive sedative-hypnotic agents and/or muscle relaxants (87). Light sedation and analgesics, however, are typically administered despite the label of being “awake.” Awake intubation techniques have been largely supplanted by induction of unconsciousness or deep sedation with or without muscle relaxation (87,88). Though the “awake intubation” is an extremely useful approach, its reduced utilization means that practitioners and their students will be less comfortable with this method through lack of experience and confidence. Its subsequent use by less experienced practitioners may complicate patient care due to poorly administered topical anesthesia, ineffective local nerve block techniques, and the lack of judicious and creative sedative/analgesic measures.
Awake intubation may benefit from the addition of a narcotic agent by providing analgesia, antitussive action, and better hemodynamic control. Many reserve an awake approach for the known or suspected difficult airway to avoid “burning any bridges” and for those with severe cardiopulmonary compromise, pre-existing unconsciousness, or marked mental or neurologic depression. However, if the patient is a poor candidate for an awake approach, or preparation for an awake approach is suboptimal, patient injury and difficult management may still ensue since an awake approach does not guarantee successful intubation nor is it devoid of morbidity or mortality (89,90,91).
Following proper preparation, unless the patient is unconscious or has markedly depressed mental status, the “awake look” technique incorporates conventional laryngoscopy to evaluate the patient's airway to gauge the feasibility and ease of intubation (46); explanation to the patient (if applicable) is imperative for cooperation. If viewing the airway structures during an “awake look” proves fruitful, intubation should be performed during the same laryngoscopic attempt either directly—grade I or II view—or by bougie assistance—grade I, II, or III—or by other means (92,93). Many “awake look” procedures that yield a reasonable view, but in which intubation is not performed, are followed by anesthetic induction with the potential for a worse view due to airway tissue collapse and obstruction by redundant tissue due to loss of pharyngeal tone. Too often, patient comfort is placed well above patient safety. The critically ill patient is often tolerant of bougie-assisted intubation (Fig. 38.14), supraglottic airway placement (e.g., LMA) (Fig. 38.15), or the placement of specialty airway devices such as the rigid fiberscopes following topical anesthetic application, local nerve blocks, or even light sedation (24,93,94,95,96).
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Figure 38.14. Array of tracheal “bougies” used to access the airway in difficult situations. |
Sedated to Asleep Techniques
Titration of medication to provide amnesia, analgesia, anxiolysis, sedation, or a combination of these desirable effects with the goal of providing comfort while preserving spontaneous ventilation is possible (44,97). Muscle relaxants may be added as an option if pharmacologic attempts to render the patient accepting of airway manipulation prove suboptimal or unsatisfactory. Sedation and amnesia are mandatory when paralysis is induced (43,44,87,88). The variety of agents available to render the patient accepting of airway manipulation and ultimately tracheal intubation have been outlined previously. Though more physical effort is required when spontaneous ventilation is maintained, allowing continued respiratory efforts may assist the practitioner in navigating the ET successfully into the trachea by the appreciation of audible breaths via the ET, coughing after intubation, ventilation bag expansion/contraction, vocalization with esophageal intubation, following the pathway of bubbles percolating around the otherwise hidden glottis, or the “up and down” movement of secretions that may offer direction in the difficult-to-visualize airway (43,44,76,87,88). Breath-holding, glottic closure, laryngospasm, swallowing, biting, jaw clenching, and gagging may contribute adversely to the intubation process, but most of these are overcome with patience and the acceptance that these are “signs of life.” In difficult situations, titration techniques that provide sedation/analgesia offer the opportunity to abort such “signs of life” with the hope of returning the patient to his or her previous state at a later time (30,63,64). The “awake” approach is accomplished by the application of topical local anesthetics and/or local nerve blocks or simply proceeding without medication based on the concurrent suppression of mental status and gag reflexes.
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Figure 38.15. Laryngeal mask airways for emergent/difficult intubation. A: The intubating laryngeal mask airway (LMA). B: Various sized LMAs for patients of different sizes and ages. |
Rapid Sequence Intubation
Rapid sequence intubation (RSI) refers to the administration of an induction agent followed by a neuromuscular blocking agent, with the goal of hastening the time needed to induce unconsciousness and muscle paralysis based on a concern for aspiration of orogastric secretions. By minimizing the time the airway is unprotected, the risk of aspiration theoretically should be reduced. Preoxygenation is paramount since oxygenation/ventilation efforts via a bag-mask during the induction process are not typically carried out, thus hypothetically avoiding esophagogastric insufflation (41,98,99). Cricoid pressure is applied, in theory, to reduce the risk of passive regurgitation of any stomach contents (29). These practices during an RSI may not always be practical nor able to be carried out, since patients do desaturate during the apneic phase of the RSI, particularly in obesity, pregnancy, poor or suboptimal preoxygenation efforts or the presence of cardiopulmonary pathology.
If needed, bag-mask support should be delivered despite the concern about esophagogastric insufflation and subsequent regurgitation/aspiration. Additionally, the application of cricoid pressure—both quantitative and qualitative—is so variable that concerns with its ubiquitous use and overall effectiveness have been raised (100,101,102,103,104). Cricoid pressure may actually improve or worsen the laryngoscopic view, plus impede mask ventilation; hence, adjustment or release of cricoid pressure should be considered in these circumstances. Further, cricoid pressure may alter the ability to place accessory devices, such as the LMA, and impede fiberoptic viewing (105,106,107,108). Despite these potential limitations of cricoid pressure, no desaturating patient—high risk for aspiration or not—should have bag-mask ventilation support withheld because of the fear of aspiration.
When performing an RSI or, for that matter, any induction method involving a neuromuscular blocking agent, an understanding of ventilation, and intubation options in the event conventional methods fail, and a preplanned strategy to assist the patient must be in place prior to induction. The development of such strategies during a crisis is difficult, often short-sighted and incomplete, and may be counterproductive and destructive to patient care. Education, training, and immediate access to airway rescue equipment that the practitioner can competently incorporate in an airway crisis is a goal worthy of expanded effort, time, and finances (30,41,43,45,46,63,64).
The proponents of rapidly controlling the airway using RSI cite a reduction in the risk of aspiration as a main thrust for this technique. Moreover, an RSI is said to be associated with a lower incidence of complications and higher first-pass intubation success rate as compared to the “sedation only” method (41,43,98,99). A predetermined induction regimen, such as etomidate and succinylcholine, is popular, easy to teach and replicate, easy to administer (e.g., 0.25 mg/kg IBW etomidate and 0.25 mg/kg IBW of succinylcholine), requires little planning or forethought, can be standardized, and, most importantly, generally works well for most critically ill patients. Though the standard dosing regimen of succinylcholine is 1 to 1.5 mg/kg, the authors find that a variety of doses may fit the needs of the operator. One should consider that the higher the dose administered, the longer the duration to recover (patient-initiated spontaneous ventilation).
Nevertheless, it appears that this approach is so commonly practiced by some individuals that it becomes the chosen induction regimen, with little regard for the patient's individual clinical condition and airway status. Several authors tout near-perfect success rates with RSI coupled with a minimum number of complications (41,43,98,99). This “slam-dunk” approach may not be the best for a significant number of the critically ill patients, namely the obese, the known or suspected difficult airway patient, the hemodynamically unstable patient, or those with significant cardiopulmonary compromise, such as pulmonary embolism, cardiac tamponade, and/or myocardial ischemia. Though there is little argument that many intubations may be made easier by the administration of a muscle relaxant, selective use based on the patient evaluation and clinical circumstances is the best option (30,44,45,46,63,64,70,72,87,88).
Positioning the Patient
One of the most important factors in improving the success rate of orotracheal intubation is positioning the patient properly (Fig. 38.3). Classically, the sniffing position, namely cervical flexion combined with atlanto-occipital extension, will assist in improving the line of sight of the intubator. Bringing the three axes into alignment (oral, pharyngeal, and laryngeal) is commonly optimized by placing a firm towel or pillow beneath the head (providing mild cervical flexion) combined with physical backward movement of the head at the atlanto-occipital joint via manual extension. This, when combined with oral laryngoscopy, will improve the “line of sight” for the intubator to better visualize the laryngeal structures in most patients (46). Optimizing bed position is imperative, as is the angle at which the patient lies on the bed. The variety of mattress material (air, water, foam, gel) provides a challenge to the practitioner since these mattresses may worsen positioning characteristics in an emergency setting. Optimizing the position of the obese (Fig. 38.12, left panel) patient is an absolute requirement to assist with (a) spontaneous ventilation and mask ventilation; (b) opening the mouth; (c) gaining access to the neck for cricoid application, manipulation of laryngeal structures, or invasive procedures; (d) improving the “line of sight” with laryngoscopy; and (e) prolonging oxygen saturation after induction (109,110,111,112,113). A ramp is constructed with blankets, a preformed wedge, or angulation of the mechanical bed to bring the ear and the sternal notch into alignment by ramping the patient's head, shoulders, and upper torso, thus facilitating spontaneous ventilation, mask ventilation, and laryngoscopy. The extra time spent to properly position the patient will reap great benefits (77,110,113).
Blade Use
The Curved Blade
Following opening of the mouth, either by the extraoral technique (finger pressing downward on chin) or the intraoral method (the finger scissor technique to spread the dentition), the laryngoscope blade is introduced at the right side of the mouth and advanced to the midline, displacing the tongue to the left. The epiglottis is seen at the base of the tongue and the tip of the blade inserted into the vallecula. If the oropharynx is dry, lubricating the blade is helpful; otherwise, suctioning out excessive secretions may assist greatly in visualizing airway structures. The laryngoscope blade should be lifted toward an imaginary point in the corner of the wall opposite the patient to avoid using the upper teeth as a fulcrum for the laryngoscope blade. Moreover, a forward and upward lift of the laryngoscope and blade stretches the hyoepiglottic ligament, thus folding the epiglottis upward and further exposing the glottis. As a result, the larynx is suspended on the tip of the blade by the hyoid bone. The practitioner's right hand, prior to picking up the ET, should be used to apply external pressure on the laryngeal cartilage (thyroid cartilage) to potentially afford better visualization of the glottis. OELM (Fig. 38.8), as this maneuver is called, is optimized and turned over to an assistant who attempts to replicate the optimal position for the operator's viewing. This description, while obviously optimal, is not always feasible.
With visualization of the glottic structures, the ET is passed to the right of the laryngoscope through the glottis into the trachea until the cuff passes 2 to 3 cm beyond the vocal cords. As described earlier, a Lehane-Cormack grade II or III airway may preclude easy placement of the tracheal tube. Thus, a blind guide underneath the epiglottis (tracheal tube introducer, bougie) or a rigid fiberoptic stylet may be incorporated to improve the insertion success rate.
The Straight Blade
Intubation with a straight blade involves the same maneuvers but with one major difference. The blade is slipped beneath the epiglottis, and exposure of the larynx is accomplished by an upward and forward lift at a 45-degree angle toward the corner of the wall opposite the patient. Again, leverage must not be applied against the upper teeth.
With either technique, the common causes of failure to intubate include inadequate position of the head, misplacement of the laryngoscope blade, inadequate muscle relaxation, insufficient depth of sedation/analgesia or general anesthesia, obscuring of the glottis by the tongue, and lack of familiarity with the anatomy, especially where pathologic changes are present. Inserting a laryngoscope blade too deeply, usually past the larynx and into the cricopharyngeal area, results in lifting of the entire larynx. If familiar landmarks are not appreciated, stop advancing the scope, withdraw the blade, and start over. If more than 30 seconds have passed or there is evidence that the oxygen saturation has dropped from the prelaryngoscopy level, bag-mask support to reoxygenate the patient is imperative. There is now evidence that repetitive laryngoscopies are not in the best interest of patient care and may place the patient at extreme risk for potentially life-threatening airway-related complications (44,45). Unless the first one to two laryngoscopy attempts were performed by less experienced members of the team, attempts at conventional laryngoscopy alone to intubate the trachea should be abandoned in favor of incorporating an airway adjunct to assist the clinician in hastening the process of gaining airway control (30,44,45,63,64,114,115).
Nasotracheal Intubation
Nasotracheal intubation, once the mainstay approach in the emergency setting, is still commonly used in oral and maxillofacial operative interventions, but less commonly in emergency situations outside the operating room. Nasotracheal intubation is an alternative to the oral route for patients with trismus, mandibular fracture, a large tongue, or edema of the oral cavity or oropharynx, and is a useful approach for the spontaneously breathing patient who refuses to lie supine or in the presence of excessive secretions. The presence of midfacial or posterior fossa trauma and coagulopathy are absolute contraindications to this technique. Thus, it is best avoided in patients with a basilar skull fracture, a fractured nose, or nasal obstruction. It is also contraindicated in the presence of acute sinusitis or mastoiditis. Additionally, as the nasal portal dictates a smaller-diameter tracheal tube, it must be remembered that as downsizing takes place, the length of the tracheal tube is shortened; hence, the length must be considered when placing a small-caliber tube (e.g., a 6.0-mm diameter in an individual taller than about 69 inches), as the nasal tracheal tube may end up as an elongated nasal trumpet, without entrance into the trachea (116,117,118).
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Figure 38.16. Magill forceps for manipulating the endotracheal tube into the glottis. These come in several sizes. |
The method of intubation via the nasal approach is variable. It may be placed blindly during spontaneous ventilation, combined with oral laryngoscopic assistance to aid with ET advancement utilizing Magill forceps (Fig. 38.16); utilize indirect visualization through the nares via an optical stylet (Fig. 38.17) or a flexible (Fig. 38.18) or rigid fiberscope (Fig. 38.19); or incorporate a lighted stylet (Fig. 38.20) for transillumination of the laryngeal structures (78,119,120).
Technique
The patient may be prepared for the nasal approach by pretreatment of the mucosa of both nostrils with a solution of 0.1% phenylephrine and a decongestant spray such as oxymetazoline for 3 to 10 minutes. This is followed by progressive dilation, starting with either a 26 French or 28 French nasal trumpet, and progressing to a 30 French to 32 French trumpet lubricated with 2% lidocaine jelly (Fig. 38.13). The method is relatively expedient. Conversely, placement of cotton pledgets soaked in a mixture of vasoconstrictor agent and local anesthetic is equally effective if one is experienced with the nasal anatomy and the proper equipment is available. Supplemental oxygen may be provided by nasal cannulae placed between the lips or via a face mask. The patient is best intubated with spontaneous ventilation maintained, yet incremental sedation/analgesia may be provided to optimize patient comfort and cooperation. Sitting upright has the advantage of maximizing the oropharyngeal diameter (116,121).
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Figure 38.17. An optical stylet, allowing visualization of the glottis as the endotracheal tube is advanced. |
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Figure 38.18. A fiberoptic bronchoscope with associated cart as used at Shands Hospital at the University of Florida. |
Orientation of the tracheal tube bevel is important for patient comfort and to reduce the risk of epistaxis and tearing or dislocation of the nasal turbinates. On either side of the nose, the bevel should face the turbinate (away from the septum). Due to bevel orientation, the tracheal tube's manufactured curve (concavity) may be facing posterior “toward the patient's face” (left nares) or anterior (right nares); once the ET reaches the nasopharynx, the concavity of the tube should face posteriorly.
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Figure 38.19. A rigid bronchoscope. |
In the ICU setting, this approach may be helpful in those with restricted cervical spine motion, trismus, and oral cavity swelling/obstruction, to name but a few conditions of interest. Awake, sitting upright with spontaneous ventilation is an ideal setting for nasal intubation. The blind approach is best accomplished with ventilation preserved. Topically applied local anesthetics, local nerve blocks, and judicious sedation and analgesia supplement the awake approach. Warming the tracheal tube combined with generous lubrication will assist rotation and advancement while providing a soft and pliable airway to reduce injury to the nasal mucosa or turbinates. Tube advancement should be slow and gentle, with rotation when resistance is encountered. Excessive force, rough maneuvers, poor lubrication, and use of force against an obstruction should be discouraged. If advancement is met with resistance from glottic/anterior tissues, helpful maneuvers to overcome these obstacles include sitting the patient upright, flexing the head forward on the neck, and manually pulling the larynx anteriorly. Conversely, if advancement is met with posterior displacement into the esophagus, sitting the patient upright, extending the head on the neck, and applying posterior-directed pressure on the thyrocricoid complex may assist in intubation. Rotation of the tube and manual depression or elevation of the larynx may be required to succeed. Voluntary or hypercapnic-induced hyperpnea helps if the patient is awake because maximal abduction of the cords is present during inspiration. Entry into the trachea is signified by consistent breath sounds transmitted by the tube and inability to speak if the patient is breathing, as well as by lack of resistance, often accompanied by cough. Often one can then feel the inflation of the tracheal cuff below the larynx and above the manubrium sterni, followed by connecting the tube to the rebreathing system and expanding the lungs (122). Confirmation with end-tidal CO2 measurement or fiberoptic viewing is imperative. Application of a specially designed airway “whistle” that assists the clinician with spontaneous ventilation intubation may be advantageous (123).
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Figure 38.20. A lighted stylet (Lightwand) for blind insertion of an endotracheal tube. Utilization of this technique requires significant practice. |
Nasotracheal intubation may also be accomplished with fiberoptic assistance. When the blind approach is met with difficulty, the fiberoptic adjunct may expedite intubation, but may be of limited assistance if secretion control is poor or if relied upon as a salvage method following nasal trauma. However, use of a fiberoptic bronchoscope is an excellent choice for the primary nasal approach with the patient sitting upright and the intubator preferentially standing in front or to the side of the patient as opposed to “over the top” (124,125). Advancement of the ET into the glottis may be impeded by hang-up on the laryngeal structures: The vocal cord, the posterior glottis, or, typically, the right arytenoid (126,127). When resistance is met, a helpful tip is as follows: withdrawing the tube 1 to 2 cm, rotate the tube counterclockwise 90 degrees, then readvance with the bevel facing posteriorly (126,127). Matching the tracheal tube to the fiberscope to minimize the gap between the internal diameter of the tube and the scope may also improve advancement (126). Tracheal confirmation and tip positioning are added advantages to fiberoptic-assisted intubation.
Complications of Nasal Intubation
Though the nasally placed ET has the advantage of overall stability, the nasal approach has decreased in popularity due to a restriction of tube size, the potential to add epistaxis to an already tenuous airway situation, the potential for sinus obstruction and infection beyond 48 hours, nasal tissue damage, and perceived discomfort during insertion. Nasotracheal intubation can cause avulsion of the turbinate bone when the tube engages the anterior end of the middle turbinate's lateral attachment in the nose and forces the avulsed turbinate into the nasopharynx (116,117,118,128,129). Additionally, prolonged nasotracheal intubation may contribute to sinusitis, ulceration, and tissue breakdown (117,130,131).
Intubation Adjuncts
Indirect Visualization of the Airway
Fiberoptic Bronchoscopy
There is an immense amount of interest in advancing airway management well beyond simply placing a laryngoscope blade into the oropharynx in the hopes that tracheal intubation can be quickly and easily accomplished. It is the critically ill ICU patient who precisely would benefit from improving the “line of sight,” a straight line from the operator's eyes to the level of the glottic opening (71,72,80,132). Being able to see “around the corner” is immensely important when one's goal is to minimize intubation attempts and hasten the time to securing the airway (74,77,78,79,83). Flexible bronchoscopy is the gold standard in indirect visualization of the airway. Its role in the critically ill ICU patient is as broad as it is adaptable to various clinical scenarios, and serves many life-saving roles, both diagnostic and therapeutic. Flexible bronchoscopy does require expertise and patience and may be limited by secretions and edema (124). Its role in tracheal intubation in the critically ill patient probably best lies in its use as a first-line technique (124), rather than as a rescue technique (26,115,132,133) (Table 38.4). Edema, secretions, and bleeding often complicate visualization of the airway following multiple failed conventional laryngoscopies, thus leaving fiberoptic capabilities limited.
Incorporating a portable TV monitor to broadcast the fiberoptic view (Fig. 38.18) to the airway team is an excellent teaching modality, plus it allows input by other team members to optimize communication, positioning, and other maneuvers to hasten the intubation process (124,134). Fiberoptic intubation effectiveness is reduced by inadequate patient preparation (e.g., topical local anesthesia application when mucosal desiccation or excessive secretions are present, or excessive sedation in an attempt to counter poorly functioning topical anesthesia coverage or inadequate local anesthesia blocks). An inexperienced practitioner, one of the prime reasons for failure or suboptimal or no assistance (hence the inability to provide adequate jaw thrust or lingual retraction); improper choice of equipment (using a pediatric-sized bronchoscope to place a 9.0 ET); and improper positioning (utilizing the supine approach in a morbidly obese patient) all will impact negatively on success. An awake technique chosen in an uncooperative patient, the lack of bronchoscope defogging, inadequate lubrication, and poor judgment in the approach (e.g., a nasal fiberoptic approach in the face of a coagulopathy or nasofacial abnormalities, or a fiberoptic approach when patient has excessive, uncontrollable secretions or bleeding) further contribute to failure and frustration. Inadequate patient preparation with medication (e.g., too light sedation leading to discomfort or an uncooperative patient, or excessive sedation leading to hypoventilation, airway obstruction, or excessive coughing or procedural pain due to lack of narcotic administration) will place an undue and likely uncorrectable burden on the fiberoptic technique.
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Table 38.4 Clinical uses of fiberoptic bronchoscopy in the intensive care unit |
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Table 38.5 Keys to fiberoptic intubation success |
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Successful fiberoptic intubation is dependent on a wide range of factors, each being performed in a timely manner (Table 38.5). Any single factor that is neglected or improperly executed may hamper the fiberoptic effort; hence, the practitioner's inexperience is a primary factor in both failures and difficulty encountered. A properly prepared and positioned patient undergoing fiberoptic nasal intubation may become a challenge—or the procedure may even fail—if too large an ET is chosen to pass through the nasal cavity or when arytenoid hang-up is encountered upon advancing the ET without counterclockwise rotation (124).
Video-laryngoscopy and Rigid Fiberscopes
In an effort to overcome the difficulty of “seeing around the corner,” various advancements have been made to the standard laryngoscope. Though a difficult-to-visualize glottis is reported to be uncommon (22), Kaplan et al. reported that direct laryngoscopy in a large cohort of elective general anesthesia patients had a Lehane-Cormack view of III or IV in 14% despite maneuvers to optimize viewing with a curved laryngoscope blade (71). The incidence of a grade III/IV view in the emergency intubation population is more than double this rate; hence the need to improve visualization capabilities “around the corner” (44,135).
The addition of optical fibers or mirrors plus design alterations have improved one's line of sight over conventional blades. Devices such as the Bullard (20,22,76) (Fig. 38.21) and the Wu scopes (25,136,137,138) and the Upsher-Scope rigid fiberscopes (138) provide unparalleled visualization of the airway in most instances and may be particularly useful in the presence of restricted cervical mobility (18,74,75). Each has an eyepiece for viewing via fiberoptic bundles for a single operator but may be attached to a teaching video head for team viewing and instruction (124,134). Video capabilities allow viewing on a television monitor, pushing video-laryngoscopy to a new and higher level of sophistication. The Macintosh (curved) video-laryngoscope (Karl Storz Endoscopy) was developed and produced by modifying a standard laryngoscope to contain a small video camera (71,139). Currently, improvements in video screen resolution, portable power sources, and the refinement in optics have afforded a new class of airway devices to assist in management of the difficult airway in the operating room, the ICU, and even remote floor locations (78,135,137,140). Alterations of the curved blade with an approximate 60-degree tip deflection separate the GlideScope and McGrath scope from the others. Though visualization is excellent, a principal observation to appreciate is that these instruments allow visualization, but they do not perform intubation of the trachea. Visualization of structures with failure to intubate is uncommon (less than 4%) (140,141), though various ET maneuvers and the use of a bougie may overcome many of these failures (142). The effectiveness and efficiency of these advanced devices require an understanding of their proper use, preparation, and restrictions, as well as practice on a normal airway before one ventures to use one in an emergency situation or a potentially difficult airway.
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Figure 38.21. Bullard intubating laryngoscope. |
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Figure 38.22. The Airtraq laryngoscope. |
A recent addition to advanced airway management is a disposable, low cost, J-shaped rigid optical laryngoscope utilizing mirrors and lenses, and which offers a clear and panoramic view of the glottic structures when placed midline in the lower airway (143). The Airtraq laryngoscope (Fig. 38.22) is an excellent adjunct for tracheal intubation, for evaluating the difficult airway for extubation, and for providing impressive indirect viewing of the glottic structures of the difficult airway during ET exchange (144). For advancement into the airway, a minimum amount of mouth opening must exist; its bulky dimensions may limit its use in the presence of a Halovest and restricted mouth opening.
Optical Stylets
Another class of intubation adjuncts that are very useful in improving success in the difficult-to-visualize airway (Lehane-Cormack grade III/IV) is the fiberoptic tracheal tube introducer or stylet. Typically fashioned like a stylet, the ET is loaded onto the fiberoptic shaft and then the stylet is maneuvered into the trachea. Visualization via an eyepiece on the scope or from a video screen affords a view of the airway structures that would otherwise remain restricted or blind (18,19,77,78,135). The ability to navigate the ET-loaded stylet past airway structures and visually confirm entrance into the trachea may hasten intubation in the difficult airway that otherwise would be considered difficult or impossible with conventional laryngoscopy (77,135,145). Again, edema, secretions, mucosal swelling, and limited mouth opening, as well as operator inexperience, may limit visualization capabilities (135). Several manufacturers produce relatively inexpensive hand-held rigid fiberoptic stylets that facilitate “seeing around the corner”; hence, they can be transported to the bedside in the ICU or to remote locations throughout the hospital (77,78,135). The use of these devices is improved by optimal positioning, lubrication, defogging, warming the ET/scope, secretion control, and, above all, practice under controlled conditions prior to deployment in the emergency setting (77,78,80,135).
Tracheal Tube Introducer/Bougie
The tracheal tube introducer (TTI, or bougie) (Fig. 38.14) has earned a position in anesthesia care as an effective airway adjunct by assisting navigation of the ET into the trachea when anatomic constraints and/or an overhanging epiglottis limit the view of the glottic opening. A grade II (arytenoids and posterior cords only) or grade III laryngeal view (epiglottis only) is ideal for bougie-assisted intubation (93,146). The TTI is listed as a rescue option in national guidelines and should be included in a difficult airway cart or portable bag (30,31,63,64). The advantages of the bougie include low cost, no power supply, portability, a rapid learning curve, minimal set-up time, and a relatively high success rate and its immediate use reduces intubation-related complications (93,146). Placement involves passing it underneath the epiglottis with further navigation through the glottis to a depth of 20 to 24 cm, with potential tactile feedback as the curved tip bounces over the cartilaginous trachea rings. The tracheal ring “clicks” may not be appreciated in all cases. Further gentle advancement to 28 to 34 cm leads to the “hang-up test” or Cheney test. This maneuver is useful not only for bougie-assisted intubation itself, but also when ET verification maneuvers and devices are imprecise or confusing. Passing the ET is assisted by laryngoscopy to clear the airway of obstacles, lubricating the ET, and counterclockwise rotation to limit arytenoid hang-up of the ET tip. The bougie's role in difficult airway management is underappreciated and, given its potentially prominent role as a simple “no frills” airway tool, more attention to its position in an airway management strategy is warranted (114,115,147).
Confirmation of Tracheal Intubation
Physical Examination
Confirmation of ET location following intubation is imperative to optimize patient safety (30,46,63,64,89,91,92,148,149). Indirect clinical indicators of intubation such as chest excursions, breath sounds, tactile ET placement test, ET condensation, observing abdominal distension or auscultating the epigastrium, and oxygen saturation monitoring are considered nonfail-safe methods since each may be lacking, misinterpreted, or falsely negative or positive in the elective setting, and this fallibility is exaggerated in the emergency setting (149). Clinician interpretation of these and many other clinical findings in an acutely ill patient in a noisy environment under adverse conditions is marginal at best (149). Even experienced personnel are plagued by inadequacies of their interpretation and understanding (89,91,92). Nonetheless, and notwithstanding these limitations, our practice for initial confirmation of ET placement is as follows:
1. Observation of the ET passing through the vocal cords
2. Chest rise with bagging
3. Presence of condensation upon exhalation
4. Absence of gurgling over the stomach
5. Presence of breath sounds over the lateral midhemithoraces
6. Presence of CO2 (Fig. 38.23)
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Figure 38.23. Disposable colorimetric CO2 detector. Yellow signifies the presence of CO2, violet its absence. |
Capnography
To supplement the clinician's skill of accurately assessing ET location, the identification of exhaled CO2 via disposable colorimetric devices or capnography should be considered an accepted standard of practice for elective as well as out-of-the-operating-room intubation (30,46,148). Considered “almost fail-safe,” these methods may fail due to a variety of causes, namely the disposable colorimetric devices may fail in low-flow or no-flow cardiac states (no pulmonary blood flow as a source of exhaled carbon dioxide), or the color change may fail or confuse the clinician due to simple misinterpretation or more commonly by soilage from secretions, pulmonary edema fluid, or blood. Conversely, capnography may fail due to temperature alterations (outside, helicopter rescue), soilage of the detector, battery or electrical failure, or equipment failure due to age, missing accessories, or lack of maintenance.
Other Devices
Esophageal detector devices, either the syringe or the self-inflating bulb (Fig. 38.24) models, assist in the detection of ET location based on the anatomic difference between the trachea (an air-filled column) and the esophagus (a closed and collapsible column) (150). Applying a 60-mL syringe to the ET and withdrawing air should collapse the esophagus, while the trachea should remain patent. This concept was simplified by replacing the syringe with a self-inflating bulb that can be attached to the ET following placement. Either compression of the bulb prior to attachment to the ET or following attachment may still lead to false-negative results (no reinflation even though the ET is in the trachea) in less than 4% of cases (150). Failures of this technique include ET soilage, carinal or bronchial intubation in the obese, and those with severe pulmonary disease (chronic obstructive pulmonary disease [COPD], bronchospasm, thick secretions, or aspiration), and gastric insufflation. This technique is not affected by a low-flow or arrest state and, hence, it may be useful when capnography or colorimetric devices fail (150,151,152).
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Figure 38.24. Esophageal detector devices, either the syringe or the self-inflating bulb models, assist in the detection of endotracheal tube location based on the anatomic difference between the trachea (an air-filled column) and the esophagus (a closed and collapsible column). Note that a 15 mm adaptor inserts onto the tip of the bulb syringe so that the connection may be made. |
Two techniques considered infallible or fail-safe when used under optimal conditions are extremely accurate in detecting and confirming ET position: (a) visualizing the ET within the glottis and (b) fiberoptic visualization of tracheal/carinal anatomy (46). However, the critically ill population may have limited glottic visualization on laryngoscopy in up to 33% of cases (44,135). Following intubation, visualization of laryngeal structures may be obscured due to the presence of the ET. Likewise, fiberoptic visualization may be hampered by secretions and blood, as well as access to and the expertise to use such equipment.
Cheney Test
A clinically useful adjunct for assisting in the verification of the ET location includes the hang-up test, consisting of passing a bougie or similar catheterlike device for the purpose of detecting tip impingement on the carinal or bronchial lumen. Typically, gently advancing a bougie to 27 to 35 cm depth may allow the practitioner to appreciate hang-up on distal structures as compared to unrestricted advancement if the ET is in the esophagus (153).
Depth of Endotracheal Tube Insertion
Classic depth of insertion is height and gender based, as well as impacted by the route of ET placement (i.e., oral vs. nasal) and the patient's intrinsic anatomy. The depth will vary with head extension/flexion and lateral movement. Final tip position is best at about 2 to 4 cm above the carina to limit irritation with head movement and patient repositioning. Typically, the height of the patient is most specific in determining ET tip depth. ET depth in the adult patient less than or equal to 62 inches (157 cm) in height should be approximately 18 to 20 cm; otherwise, 22 to 26 cm may be the appropriate depth. Chest radiography only determines the tip depth at the time of film exposure. Fiberoptic depth assessment is the real-time method that garners the most clinical data for diagnostic and therapeutic purposes (123,154).
American Society of Anesthesiologists Practice Guidelines
These guidelines and others specifically suggest that airway management procedures should be accompanied by capnography or similar technology to reduce the incidence of unrecognized esophageal intubation, hypoxia, brain injury, and death (30,63,64). We can think of no reason, in the economically advanced countries, why these recommendations would not be followed.
American Society of Anesthesiologists Difficult Airway Practice Guidelines
Though reviewed earlier in this chapter, the salient points of the algorithm (Table 38.6) as they relate to the critically ill patient requiring emergency airway management are well worth repeating. Preintubation evaluation in the hopes of recognizing the difficult airway is paramount, yet is meshed with the understanding that the unrecognized or underappreciated difficult airway (mask ventilation, intubation, or both) occurs frequently. Examination of the patient, however, may be restricted due to emergent conditions, and the medical record may provide little to no useful data, especially when the patient previously had an easily managed airway but the airway status has changed substantially. When difficulty is known or predicted, patient preparation and access to airway equipment become primary focal points. This is not the case with the unrecognized or underestimated difficult airway. The induction technique is obviously not customized to the known difficulty; hence, the practitioner must counter this “surprise” by a preplanned rescue strategy, immediate access to advanced airway equipment, and personnel assistance combined with the expertise and competence to initiate and accomplish such a rescue strategy (30,63,64).
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Table 38.6 American Society of Anesthesiologists difficult airway algorithm |
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Figure 38.25. Large-bore IV catheter and tubing for emergency airway. This is useful for emergency jet ventilation. |
Primary questions for the practitioner when accessing the patient are:
1. Is there a reasonable expectation for successful mask ventilation?
2. Is intubation of the trachea expected to be problematic?
3. Should the airway approach be nonsurgical or surgical?
4. Should an awake or a sedated/unconsciousness approach be pursued?
5. Should spontaneous ventilation be maintained?
6. Should paralysis be pursued (30)?
With forethought and experience, these considerations may be answered rapidly following patient assessment. Conversely, a predetermined strategy that dictates an RSI “will be easy” to pursue and thus requires minimal assessment, since the technique has been predestined rather than modeled around the findings of the above considerations, is fraught with risk to the patient (30,63,64).
Awake Pathway
If difficulty is recognized, an awake approach may be appropriate, barring lack of cooperation or patient refusal and given the practitioner's familiarity with this approach. Patient preparation with an antisialogogue, assembling equipment and personnel, discussion with the patient, and optimal positioning should be pursued unless the patient conditions dictate immediate awake intervention due to respiratory distress and hypoxemia. The awake choices, following optimal preparation, may allow the practitioner to take an “awake look” with conventional laryngoscopy; utilize bougie-assisted intubation, LMA insertion, or indirect fiberoptic techniques (rigid and flexible); or proceed with a surgical airway. The Combitube would not be indicated in the awake state. Access to the airway via cricothyroid membrane puncture via large-bore catheter insertion (Fig. 38.25A) with either modified tubing or a jet device (Fig. 38.25B) to ventilate, or Melker cricothyrotomy kit (Fig. 38.26) is an option prior to other awake or asleep methods, but is often forgotten and rarely executed. If the awake approach fails or the patient deteriorates, prompting rapid intervention, the rescue strategy must be pursued immediately (6,46,155,156).
Asleep Pathway
Following induction in the patient with a known or suspected difficult airway who is uncooperative or agitated, or in the unrecognized difficult airway, the ability to provide adequate mask ventilation will determine the direction of management. If mask ventilation is adequate but conventional intubation is difficult, incorporating the nonemergency pathway is appropriate, utilizing the bougie, specialty blades, supraglottic airway, flexible or rigid fiberoptic technique, or surgical airway (30,46). If mask ventilation is suboptimal or impossible, intubation of the trachea may be attempted, but immediate placement of a supraglottic airway such as the LMA is the treatment of choice. When entering the emergent pathway, if the supraglottic device fails, then an extraglottic device such as the Combitube or similar device may be placed; otherwise, transtracheal jet ventilation may be pursued by personnel knowledgeable in its application and execution, or a surgical airway placed (30,46).
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Figure 38.26. The Melker cricothyrotomy kit for emergency subglottic access to the airway. |
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Table 38.7 Strategy for emergency airway management of the critically ill patient |
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A recently suggested strategy for emergency airway management of the critically ill patient outside the operating room is shown in Table 38.7 (114,115). Patient care was compared before (no immediate access to rescue equipment or ETCO2 monitoring) and after (immediate access to rescue equipment and ETCO2 monitoring) the management strategy was in place. A substantial improvement in patient care was realized with the following strategy: Hypoxemia, defined as SpO2 <90%, was reduced from 28% to 12%; severe hypoxemia, defined as SpO2 <70%, was reduced by 50%; esophageal intubation was reduced by 66%; multiple esophageal intubations were reduced by 50%; regurgitation and aspiration were reduced by 87%; and the rate of bradycardia fell by 60%. Any rescue strategy, however, should be customized to the practitioner's skill level, his or her access to rescue equipment, and his or her knowledge and competence of using such equipment (113,114). Similar strategies have been used in the operating room with an improved margin of safety for airway management (84,85,147).
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Table 38.8 Risks of tracheal intubation |
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Complications Related to Accessing the Airway
Tracheal intubation is an important source of morbidity and, occasionally, of mortality (30,43,44,45,46,89,91,92,148). Complications occur in four time periods: during intubation, after placement, during extubation, and after extubation (Table 38.8). Patients with smaller airways, especially infants and children, have a higher incidence of complications, combined with an increased risk of upper airway obstruction secondary to glottic edema and subglottic stenosis.
Cuffed tube usage for prolonged intubation and artificial ventilation substantially increases the rate of tracheal and laryngeal injury. The extent of injury is dependent on duration of exposure, the presence of infected secretions, and severity of respiratory failure. Cuff pressures above 25 to 35 mm Hg further add to risk by compressing tracheal capillaries, which predisposes to ischemic mucosal damage despite the high-volume, low-pressure cuffs that are standard today (157,158,159,160). Other factors of importance include the duration of intubation, reintubation, and route of intubation, with nasal intubation producing more complications than oral; patient-initiated self-extubation; excessive tracheal tube movement; trauma during procedures; and poor tube care. As one might expect, clinicians unskilled in intubation techniques increase the complication rate.
During Intubation
Trauma
Tracheal intubation dangers begin at the time of initial tube insertion. Direct airway trauma depends on operator skill and the degree of difficulty encountered during intubation (27). Injuries include bruised or lacerated lips and tongue, inadvertent tooth extraction, upper airway hemorrhage, vocal cord tears, and nasal polyp dislodgement. Inadvertent contact of the cornea by the operator's hand may cause a corneal abrasion. Nasopharyngeal mucosa perforation can create a false passage, whereas a tear in the pyriform fossa mucosal lining may lead to mediastinal emphysema, tension pneumothorax, and infectious complications (27,89,91,92). Fracture or subluxation of the cervical spine, though rare, may result from careless movement of the head or forceful hyperextension during attempts to improve laryngeal exposure (18). Laryngoscopy may lead to swelling, edema, and bleeding of the oropharyngolaryngeal complex. Pre-existing edema or a coagulopathy will only exaggerate further swelling and bleeding. Continued efforts to control the airway with conventional laryngoscopic attempts may prove detrimental if supraglottic-glottic edema/swelling/closure results from repetitive trauma. Accessory devices such as the LMA and Combitube are dependent on a patent glottic opening; thus, exacerbating tissue damage with repetitive attempts may reduce rescue success with these devices (46).
Delay
Excessive delay in cardiopulmonary resuscitation may occur while an inexperienced practitioner tries to visualize the vocal cords. If intubation cannot be accomplished within 30 seconds, a more experienced person should make the attempt whenever possible. Multiple intubation attempts by any practitioner, unskilled or skilled, may make subsequent attempts more problematic and markedly increase the risk of hypoxemia, esophageal intubation, regurgitation, aspiration, bradycardia, cardiovascular collapse, and arrest (44,45,46). If effective mask ventilation and oxygen delivery are not possible during cardiopulmonary resuscitation (CPR), then prompt placement of an accessory device (LMA, Combitube) to support ventilation and oxygenation should be pursued (30,46,63,64). The LMA may assist with tracheal intubation itself and/or support ventilation and oxygenation in lieu of intubation.
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Table 38.9 Airway complications contributing to hypoxemia |
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Airway-related Complications
Airway-related complications in the emergency setting are similar in variety but outflank their elective counterpart in magnitude, occurrence, and consequence. Excessive secretions, edema, and bleeding, especially from repetitive instrumentation, may plague these interventions. The incidences of laryngospasm, bronchospasm, bleeding, tissue trauma, aspiration, inadequate ventilation, and difficult intubation remain relatively poorly documented.
Hypoxemia
Hypoxemia during emergency intubation has a variable incidence, ranging from 2% to 28% (12,44,89,90,140,161,162,163). Currently, there is little specific literature reporting the influence of age, comorbid conditions, and pathologic states on the incidence of hypoxemia during emergency airway management, yet the risk increases as the patient's clinical situation worsens (Table 38.9) (70,163). Moreover, the patient's oxygenation reserves, obesity-related pulmonary limitations, and difficulty with airway management will influence the incidence of hypoxemia (112,164,165,166,167).
Hypoxemia-related concerns for emergency airway management include:
1. The limits of preoxygenation in the critically ill
2. The increased incidence of multiple intubation attempts
3. The increased incidence of encountering a “difficult airway” in the emergency setting (30,44,45,72,85,90)
Esophageal Intubation
Delayed recognition of esophageal intubation (EI) is a leading adverse event contributing to hypoxemia, aspiration, central neurologic system damage, and death (27,30,89,90,91,92,148,149). Failure to recognize EI is not limited to inexperienced trainees and, despite the use of verification devices, EI-related catastrophes persist (88,90,91). Indirect clinical signs of detecting tracheal tube location are imprecise and their interpretation is further restricted under emergent circumstances (Fig. 38.27) (46,89,91,149). Curbing the ill effects of EI by vigilant monitoring and rapid detection is warranted (148,149). Viewing the tube between the vocal cords, considered fail-safe, is impractical in 10% to 30% of patients due to anatomic limitations (44,168). Fiberoptic verification is fail-safe, yet is limited by blood and secretions, the operator's skill, and equipment access (124).
Regurgitation and Aspiration
Perioperative pulmonary aspiration is uncommon, occurring in approximately 1 in every 2,600 cases, but is magnified in the emergency surgical setting (169). Regurgitation during emergency intubation varies widely, ranging between 1.6% and 8.5%, with aspiration of the regurgitated material ranging between 0.4% and 5% (44,45,90,170). Emergently, there is little control over NPO status, ileus, upper gastrointestinal bleeding, or altered airway reflexes. Hypoxemia, bradycardia, and arrest may be magnified during regurgitation/aspiration (44,45,84,170). Immediate access to, and use of, accessory devices and ET-placement verifying equipment has reduced regurgitation and aspiration by 43% and 75%, respectively (148,149). Upper gastrointestinal bleeding is particularly risky, as it increases regurgitation by a factor of 4 and aspiration by a factor of 7 when compared to nonbleeding patients undergoing emergency intubation (95,171).
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Figure 38.27. Incidence of complications with (EI) and without (non-EI, i.e., tracheal intubation) esophageal intubation detected by indirect clinical signs. (From Mort TC. Esophageal intubation with indirect clinical tests during emergency tracheal intubation: a report on patient morbidity. J Clin Anesth. 2005;17[4]:255.) |
Airway Injury
The “airway” may sustain minor, nondisabling to catastrophic, life-threatening degrees of trauma during emergency intubation unbeknown to the practitioner. Difficult intubation is a factor in many, but not all, cases; for example, in several series, 50% of intubations resulting in esophageal perforations were believed to have been atraumatic intubations (27,89,91,92). Injury, shrouded by generalized nonspecific signs and symptoms combined with sedated, intubated patients unable to communicate, may limit the consideration of any injury (27,92). Pneumothorax, subcutaneous emphysema, pneumomediastinum, dysphasia, chest pain, coughing, or deep cervical pain advancing to a febrile state should be investigated (27,92).
Bronchial Intubation
Undetected bronchial intubation discovered by a postintubation chest radiograph is common, being seen in between 3.5% and 15.5% of cases. This undetected event increases substantially following difficult intubation, often leading to hypoxemia, atelectasis, bronchospasm, lobar collapse, and barotrauma if left uncorrected (44,45,172,173,174,175,176). Lung auscultation and palpation of the inflated cuff above the sternal notch may decrease bronchial intubation or carinal impingement, but are not fail-safe (122). Fiberoptic evaluation is definitive; thus, access to this modality in the ICU is important to allow for investigation of any unexplained oxygen desaturation, coughing, bronchospasm, or changes in peak inspiratory pressures, or an abrupt or gradual reduction in tidal volume (174,175,176,177,178).
Multiple Intubation Attempts
National guidelines define a difficult intubation as the inability to intubate within three attempts, at which point alternative airway techniques should be incorporated (30). Repeated interventions increase tissue trauma, bleeding, and edema, and may transform a “ventilatable” airway to one that is not (44,45,46). The number of laryngoscopic attempts directly increases complications, increasing with the second laryngoscopic attempt and accelerating rapidly with three or more attempts (44,45). All critically ill patients who require emergency airway management likely should be regarded as a potentially unanticipated difficult airway. Hence, observing the one or two attempts “rule” under “optimal conditions” before rapidly moving to an alternative strategy is prudent (27,43,44,45,46,85).
Though the literature has recommended a rapid sequence intubation technique as the definitive method of patient preparation, airways are as individual as their owners, and practitioner skills are variable. Thus, patients may benefit from an individualized approach (41,97,98). Incorporating a strategy that is adaptable to the practitioner and the patient (and his or her airway) may lead to a lower incidence of complications (27,44,45,85,86,87,88,114,115).
After Intubation
Acute Endotracheal Tube Obstruction Following Intubation
Acute ET obstruction has a differential diagnostic list that is long but, in most cases, can be discerned rapidly. Biting may be from an awake, agitated, or delirious patient or, on the other hand, the ET tip may abut the tracheal wall. A bite block in the patient's mouth, additional sedation/analgesic agents, or slight rotation of the tube may correct the obstruction. Kinking of the tube or herniation of the cuff can occlude the airway and compromise ventilation, as can blood clots, tissue, dried secretions, tube lubricants, and foreign bodies. Partial or complete obstruction (Fig. 38.28) of a newly placed ET or tracheostomy tube by intraluminal or extraluminal sources may present as a life-threatening emergency requiring immediate corrective measures to reduce the risk of hypoxia-related morbidity and mortality (155,179).
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Figure 38.28. Obstruction of the endotracheal tube by intraluminal material, in this case, a bloody mucous plug. |
Signs of ET or tracheobronchial obstruction are high inflation pressures, absent or impaired chest excursion, marked respiratory effort with paradoxical movement, cyanosis, hypoxemia, and venous congestion. Acute severe bronchospasm following primary tracheal intubation or during a tube exchange may mimic acute obstruction.
The rescue therapy differs between the in situ ET obstruction—depending upon its degree—and obstruction distal to the ET tip. Rapid removal of a completely obstructed ET may be life saving and, conversely, partial obstruction of the ET or tracheobronchial tree by inspissated mucus, blood, or tissue may require rapid irrigation and suctioning, either blindly via a suction catheter or utilizing a fiberoptic bronchoscope.
The etiology of the airway obstruction following intubation in the emergency setting in the ICU is often related to thick secretions. The patient undergoing emergency tracheal intubation may require mechanical support based on respiratory insufficiency due to poor secretion-clearing capabilities, poor cough, retained secretions, and shallow respirations. Once the trachea is intubated and positive pressure is delivered, the retained and dormant secretions mobilize more proximally toward the upper tracheobronchial tree, potentially contributing to airway obstruction. Conversely, during an ET exchange in a patient maintained on positive end-expiratory pressure (PEEP), especially when the level is approximately 8 cm H2O or above, the sudden loss of expiratory pressure during the exchange appears to allow proximal movement of retained secretions, previously undetected or unreachable by standard ET suction techniques, to rapidly migrate toward the tracheocarinal region, potentially leading to very difficult or impossible ventilation.
The incidence of such events is not precisely known, but the most devastating consequence of such airway obstruction, hypoxia-driven cardiac arrest, was noted in the Hartford Hospital database (5 arrests in over 3,000 emergently intubated patients, 0.17%) (148). One of us (TCM) with an airway database composed of over 1,800 patients who underwent primary tracheal intubation or ET exchange over a 16-year period has noted acute airway obstruction leading to arrest in four cases (0.2%) and near arrest (severe desaturation, bradycardia) in 16 cases (0.9%). Swift suction removal following irrigation of the tracheobronchial tree, ET removal, or fiberoptic evacuation of the obstruction was paramount in limiting patient injury.
Bradycardia
The response to laryngoscopy intubation is typically hyperdynamic, but in a small number of patients, slowing of the heart rate may accompany airway manipulation. Patients receiving medications which slow sinoatrial (SA) node, atrioventricular (AV) node, or ventricular conduction, in addition to the aggressive use of fentanyl or other vagotonic medications, may be at increased risk for a further slowing of the heart rate. Preintubation bradycardia due to medication, an intrinsically slow heart rate in hypertensive disease of the elderly and the physically fit, and occasionally severe hypoxemia or the Cushing reflex in elevated intracranial pressure (ICP) may place the patient at a lower threshold to experience bradycardia. Vigorous laryngoscopy and tracheal intubation, inadvertent EI, and airway-related complications with severe or prolonged hypoxemia have led to bradycardia and cardiac arrest (44,45,148,149). Moreover, progressive bradycardia has been noted to precede intraoperative cardiac arrests in the majority of cases (146,148,180,181,182). Propofol's role in bradycardia remains ill-defined, but may be more relevant in the ICU patient on a continuous intravenous infusion rather than when using the agent in a single dose for intubation.
Vagotonic influences related to airway manipulation and hypoxemia appear to be primary factors. While an uncomplicated laryngoscopy may reduce the heart rate, airway-associated complications during difficult laryngoscopy and intubation with concurrent hypoxemia increase the incidence of bradycardia dramatically (148,170). The sympathetic outflow stimulated by a moderate reduction in oxygen tension may be overwhelmed by the parasympathetic influence with ongoing or worsening hypoxemia, thus leading to medullary ischemia. In addition, the drop in heart rate is typically associated with a significant reduction in blood pressure, often requiring aggressive therapy. When confronted with bradycardia, it behooves the practitioner to optimize oxygen delivery via the rapid deployment of accessory devices, call for the code cart, and provide pharmacologic intervention as well as interventions for potentially catastrophic pathology such as a tension pneumothorax, unrecognized esophageal intubation, or mainstem bronchus intubation.
Dysrhythmias
The acute onset of a new dysrhythmia during the manipulation of the airway or immediately after completion of securing the airway is infrequently reported. Pre-existing rhythm disturbances may be exaggerated by even rapid, straightforward airway manipulation, but may pale in comparison to the response initiated by a vigorous laryngoscopy, especially if it is associated with multiple attempts, inadequate sedation, or additional myocardial compromise. Bradycardia (see above), supraventricular tachycardia, atrial fibrillation or flutter with a rapid ventricular response, and ventricular disturbances are usually poorly tolerated by the critically ill patient, often complicated by varying degrees of hypotension. Further, succinylcholine—often used in RSI—is a well-known causative factor in contributing to a multitude of atrial and ventricular rhythm disturbances. Ongoing myocardial injury or a prolonged, vigorous, or traumatic manipulation of the airway can potentiate life-threatening dysrhythmias (44,183).
Cardiac Arrest
Anesthesia-related cardiac arrest in the operating room is relatively infrequent (0.01%), with the majority related to airway mishaps/difficulties (146,180,181,182). The risk of cardiac arrest in the ICU patient during emergency airway management may be as high as 2% (44,45,148,170). Specific risk factors contributing to cardiac arrest during airway manipulation included three or more intubation attempts, hypoxemia, regurgitation with aspiration, bradycardia, and esophageal intubation, often with one or more of these complications cascading from one to another (148,149). Nonairway-related cardiac arrests may result from ET obstruction, tension pneumothoraces, massive pulmonary thromboembolism, induction medication, and deterioration in patients suffering from acute myocardial infarction with cardiogenic shock (148). The varied list of etiologic factors that may contribute, singly or in combination, to the risk of cardiopulmonary arrest and cardiovascular collapse related to tracheal intubation is noted in Table 38.10 (170). Immediate access and use of advanced airway equipment and airway-placement verifying devices appear to have a significant impact on the incidence of hypoxemia-driven cardiac arrest (148).
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Table 38.10 Factors contributing to postintubation hemodynamic instability |
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The Hyperdynamic Response to Airway Management
A brief or prolonged hyperdynamic response frequently accompanies direct laryngoscopy and intubation, and may reflect a number of physiologic factors, including wakefulness; the magnitude, vigor, and extent of the airway manipulation; underlying hypertension and cardiovascular disease; intravascular volume status; underlying sympathetic outflow; any related renal and cerebral pathology; induction medication; and the functional reserve of the patient among other clinical causes. Patients with central nervous system (CNS) pathology (stroke, intracerebral hemorrhage, seizure disorder) will have a higher likelihood of hypertension and/or tachycardia with airway manipulation (184,185,186). A persistent hyperdynamic response post intubation may reflect ongoing pain, anxiety, and/or wakefulness that may respond to additional anesthetic induction agents, or may reflect an exaggerated response seen in the high-risk individual with diabetes mellitus, renal or cardiovascular disease, or a CNS insult, and may also be seen in the intoxicated and the traumatized patient (184,185,187,188). Treatment with additional induction agents or vasodilators, diltiazem, or β antagonists may suffice, but overly aggressive treatment may quickly introduce further hemodynamic compromise when the therapy outlasts the self-limited phase of postintubation hypertension (186,187). Pathologic conditions which dictate aggressive therapy include head injury, intracerebral bleed, cerebral vascular accident, or seizure disorder.
Recognizable causes of an exaggerated hyperdynamic response may include balloon inflation, ET suctioning, mainstem bronchial/carinal impingement, coughing, bucking, or “fighting” the ventilator. The aggressive administration of anesthesia induction agents is literally a double-edged sword: capable of limiting the hyperdynamic response during airway manipulation but the quiescent, stimulation-free period that usually follows securing the airway may lead to a sharp reduction in the blood pressure (184,186).
Hypotension
The incidence of postintubation hypotension in the emergency setting is the most common of the hemodynamic alterations stemming from a variety of single and multiple etiologies (44,45,148,189,190). Being mindful of the pre-existing comorbidities and the current clinical deterioration prompting intubation, the airway manager's judgment and experience will influence the medication choices and techniques to prepare the patient for airway instrumentation. The major challenge is to select the agents that will achieve the goal of blunting, attenuating, or blocking the postlaryngoscopy hyperdynamic response, typically lasting for only a brief amount of time, with minimal subsequent influence or contribution to postintubation hypotension. Strategies are best tailored to the individual patient's needs based on the experience and judgment of the airway manager rather than, as we have commented several times previously, a standard intubation protocol such as etomidate and succinylcholine being administered to each and every patient (43,45). The addition of a neuromuscular blocking agent may impact the dosing of induction agents and the subsequent need for vasoactive medications, especially when blood pressure is maintained by agitation, struggling, straining, and muscle contraction of the critically ill patient.
The aggressive use of induction agents may potentiate the reduction in blood pressure following airway manipulation, particularly if no additional stimulation is provided post intubation. The institution of positive-pressure ventilation with PEEP plus any vasodilatation and myocardial depression from anesthetic agents may contribute to postintubation hypotension (189,190). This response is accentuated in incidence and magnitude in the critically ill patient who is struggling with underlying cardiopulmonary deterioration, acid-base imbalance, sepsis, hemorrhage, hypovolemia, and other maladies (44,148,189,190). Postintubation hypotension may require crystalloid resuscitation and/or a vasoactive agent such as ephedrine, Neo-Synephrine, vasopressin, or norepinephrine. Postintubation hypotension, per se, has not been studied in detail, though brief hypotension, in general, has been suggested as a significant contributing factor to patient morbidity and poor outcomes, especially in the traumatized and the neurologically injured patient (191).
Published reports that mention postintubation hypotension suggest that it is a rare occurrence despite the disposition of the critically ill patient. For example, two emergency department studies of nearly 1,200 patients reported less than 0.3% (four patients) developed hypotension (systolic less than 90 mm Hg) (98,99). Conversely, emergency intubation outside the operating room—including the emergency department—by anesthesiologists reported that four of every ten patients suffered hypotension requiring vasoactive medications to supplement crystalloid administration in one half of the victims (44,45,148). Nonetheless, the extent and degree of hypotension will be influenced by the induction agent, volume status, pre-existing comorbidities, and reason for the clinical deterioration, plus numerous other factors. Sepsis and cardiovascular injury such as myocardial infarction, congestive cardiomyopathy, pulmonary embolism, or cardiac tamponade appear to place the patient at greater risk for postintubation hypotension and the subsequent need for vasoactive medications.1
Age appears to play a prominent role in the incidence of postintubation hypotension: The octogenarian (52%) and nonagenarian (61%) are at higher risk as compared to those younger than 30 years old (22%) and the group between 30 and 60 years (35%). The need for vasoactive agents to counter the hypotension is twice as likely in the octogenarian and older groups when compared to those younger than 50 years old (62% vs. 30%) (192).
Endotracheal Tube Displacement/Extubation
Tube displacement out of the trachea or migration of the tube tip into a bronchus may compromise the airway (177,178). Appropriate securing and notation of tube markings in relation to the lip may minimize this complication, but the location of the markings at the dentition level has little bearing on the position of the ET tip (178,193). A chest radiograph may assist in confirming tip location, but only at the time of the filming. Fiberoptic evaluation of the tracheal tube positions offer real-time information that a chest radiograph taken 4 hours earlier cannot offer (154). Hyperextension of the head may cause migration of the tracheal tube tip away from the carina toward the pharynx; conversely, head flexion may advance the tube tip, with an average 1.9 cm movement of the tube (158).
Lateral rotation of the head may move the tube to 0.7 to 1 cm away from the carina. If tube tip position is in question and there is any clinical sign or symptom suggesting a problem (e.g., desaturation, tachypnea, and so forth), then one should consider aggressively pursuing a fiberoptically assisted determination of the tube placement rather than awaiting the call for a chest radiograph or waiting until an emergent situation has developed.
Accidental Extubation
Accidental extubation is a well-known clinical problem with the potential of significant patient morbidity and mortality (193). Accidental extubation, either patient-initiated self-extubation or resultant from external forces (nurse/physician moving patient, radiology team, transport, etc.), is another potential complication after intubation, occurring in 8% to 13% of intubated, critically ill patients (194). To prevent unplanned extubation, secure the tube by taping circumferentially around the upper neck. A variety of manufactured ET securing devices are available for purchase in lieu of the taping option. Tincture of benzoin improves adhesiveness of the tape to the skin and the tube. Restraining the patient's hands, care in turning and moving the patient, and good nursing practices minimize—but do not eliminate—this complication. Proper sedation regimens, close observation, and hastening extubation in those who meet criteria may reduce patient-initiated self-extubations (195,196).
Complete extubation of the trachea is most obvious when the patient self-extubates. However, the trachea may only be partially extubated when the ET cuff-tip complex is displaced proximally between or above the cords (193). An audible cuff leak is common, regardless of whether the final position of the ET cuff is just below, between, or proximal to the vocal cords. Moreover, complete extubation of the trachea—the cuff and ET tip lying in the hypopharynx—may present with a continuous or intermittent leak, or none at all (193). An ET secured at the lips/dentition at a level of 21 to 26 cm does not always equate to a correct tip position within the trachea (193). ET thermolability at body temperature may result in a coiled, kinked, or spirally misshaped (S-shaped) tube. If a cuff leak is heard, an attempt at remediation on a repetitive basis by adding air to the cuff may lead to further cuff-tip displacement (herniation). The hypopharynx may accommodate an ET with an overinflated cuff containing as much as 30 to 150 mL of air. Repetitive “fixing” of a cuff leak with small increments of air over several hours to days may lead to a stretched, highly compliant cuff positioned in the hypopharynx with continued ventilation and oxygenation. Cuff pressure measurements may be misleading due to altered cuff compliance and its position in the upper airway (193).
If a cuff leak—either intermittent or continuous—is noted, the pilot balloon should be checked for integrity. If inflated, the cuff-tip complex may be displaced at or above the glottic opening. Cuff deflation with blind advancement toward the airway should be discouraged by personnel not fully capable of managing the airway in the event of ET displacement, kinking, esophageal intubation, or loss of the airway. Evaluating the airway with direct laryngoscopy (DL) may be very helpful in assessing the location and status of the ET, but ET thermolability reduces one's ability to advance the softened, floppy, or deformed ET (193).
Conversely, a more proximal displaced ET (visible cuff in the hypopharynx) should not be advanced by hand unless the view of the airway is clear. Diagnostic/therapeutic bronchoscopy is the optimal choice. Diagnosing the location and deformity of the ET is possible coupled with its unparalleled utility for advancing the ET into the trachea. Secretions, operator skill, lack of immediate access to such equipment, and an ET tip abutting on the glottic, supraglottic, or hypopharyngeal structures may present reintubation challenges (193). If cuff hyperinflation is noted, complete deflation must be done prior to advancement over the fiberoptic bronchoscope (FOB). Once the airway is resecured, changing the deformed ET to a new one (via an airway exchanger cannula) may be considered (193). This clinical problem is common and life threatening; therefore, equipping the ICU with advanced airway devices is imperative (27,31,44,46).
The Failed Intubation
In the clinical situation in which the patient has been positioned to the best of the practitioner's abilities, the operator is experienced at performing the airway management intervention, and optimal efforts at conventional mask ventilation and tracheal intubation have been attempted but are unsuccessful (a CVCI [can't ventilate, can't intubate] situation), the practitioner will need to rapidly deploy his or her rescue plan in an attempt to salvage the airway and to save the patient's life. Following failure of conventional mask ventilation (no ventilation or oxygen delivery) or when mask ventilation is failing (inadequate gas exchange, SpO2 less than 90%, or a falling SpO2), a supraglottic airway (LMA) should be placed (30,46,63,64). In some instances in which mask ventilation and oxygen delivery fail, or are failing—yet prior to any intubation attempt—intubation could be attempted if it is reasonably assumed to be straightforward and can likely be rapidly completed, as in the case of a patient with a slender habitus, who is edentulous, with no obvious difficult airway risk factors. If unsuccessful, placement of the LMA or a Combitube should proceed immediately (30,46). Conversely, the Combitube may serve as a backup for LMA failure (69). Both devices have a high rate of success for ventilation, are placed rapidly and blindly, and require a relatively simple skill set. However, in the situation described, most practitioners would choose the LMA due to its wider familiarity and because it readily serves as an intubation conduit, whereas the Combitube does not (46).
Limiting intubation attempts is a key to successful management, since repeated attempts that are probably futile (e.g., a grade IV view with conventional methods) waste time; increase trauma, edema, and bleeding; and markedly increase the risk of hypoxemia and other potentially devastating complications (27,30,44,45,63,64). It must be stressed that conventional intubation failure should be supplemented by an airway adjunct such as the bougie, specialty blades, or fiberscopes if immediately available. A key point is: Use them early, and use them often.
The American Society of Anesthesiologists (ASA) guidelines list both the LMA and the Combitube as ventilatory devices in the CVCI situation as less invasive options (30,46). More invasively, transtracheal jet ventilation (TTJV) via a large-gauge (12 or 14 gauge) IV catheter through the cricothyroid membrane may be an appropriate alternative, but advanced planning with ready access to the proper equipment and a sound understanding of “jetting” principles (lowest PSI setting to maintain SpO2 in the 80%–90% range, prolonged inspiration-to-expiration ratio [i.e., 1:5], 6–12 quick breaths per minute, allowing a path for exhalation, constant catheter stabilization, and barotrauma vigilance) must be followed; otherwise, the consequences may be very serious, indeed (46,197).
It is imperative to appreciate the difference between an upper airway CVCI and a lower airway CVCI. A lower airway CVCI due to glottic abnormalities such as spasm, tumor, abscess, massive swelling, or subglottic pathology cannot be solved with a device dependent on glottic patency such as the LMA or Combitube (46). Only a subglottic approach, such as TTJV or a surgical airway, will suffice. Likewise, repetitive intubation attempts leading to airway trauma, bleeding, and edema not only markedly reduce the effectiveness of many intubation adjuncts, but also the once ventilatable airway may deteriorate into one that cannot be managed effectively, thus transforming the airway to a CVCI situation. If, however, management of an upper airway CVCI with noninvasive techniques fails, then rapid transition to TTJV or a surgical approach must be rendered (30,46,63,64). Conversely, successful ventilation and oxygen delivery via a supraglottic device does allow time to gain surgical access if intubation via the supraglottic device is difficult or fails.
All these life-saving maneuvers cannot be accomplished by carrying a laryngoscope in our back pocket or by grabbing the bare essential airway management equipment from a plastic storage bin in the ICU. Advanced planning to acquire and properly deploy conventional and advanced airway equipment, coupled with the education to execute a rescue strategy, is warranted given the precarious airway status of many critically ill patients who require airway management (30,31,46,63,64). Availability of personnel is imperative, as intubation is a team activity. The CVCI situation is very terrifying—indeed, bloodcurdling—so planning ahead to reduce the risks of airway management is both a justifiable and sound endeavor.
Laryngeal/Tracheal Damage
Prolonged intubation may cause laryngeal or tracheal injury (110,112,113,114,115,164). Excessive cuff pressure and prolonged intubation can initiate mucosal erosion, cartilage necrosis, and eventually tracheal stenosis. Movement of the tube during assisted ventilation may erode the trachea, usually in the posterior membranous portion. Blood-tinged sputum or any degree of new-onset hemoptysis should prompt evaluation of the ET or tracheostomy tube position. Erosions, granulation tissue growth, mucosal tears, and suction catheter–related trauma may contribute to bloody secretions, as may an undiagnosed lung tumor or necrotizing infectious process. Tracheal or bronchial rupture occurs more frequently in infants, the elderly, or patients with chronic obstructive lung disease. Because signs and symptoms may be delayed, chest radiographs and prompt endoscopy may confirm the diagnosis.
Miscellaneous
Other problems encountered during intubation are aspiration of gastric contents secondary to passive (silent) regurgitation, and leakage of orogastric secretions past the cuff. Regimens to cleanse the nasal and oropharyngeal cavity suggest a potential reduction in nosocomial pneumonia in the ICU setting. Paranasal sinusitis develops in 2% to 5% of nasally intubated patients and commonly involves the maxillary sinus (119,120,121). Signs and symptoms include fever and purulent nasal discharge, often appearing 2 to 4 days after nasal intubation. Infrequently, a middle ear infection results from bacterial reflux into the eustachian tube, followed by contiguous spread into the middle ear (122,123).
During Extubation
Problems during extubation arise secondary to mechanical damage, which develops while the tube is in place or in response to tissue injury. Failure to deflate the cuff, adhesion of the tube to the tracheal wall, or transfixation of the tube by a suture to a nearby structure may result in a difficult or impossible extubation. Laryngospasm and acute airway obstruction represent the most serious complications during the immediate postextubation period. Positive-pressure ventilation via a bag-mask assembly may assist in oxygen exchange, but prompt relief may require reintubation or rapid administration of a quick-onset muscle relaxant for laryngospasm. Collapse of redundant supraglottic tissue postextubation combined with rapid accumulation of laryngeal edema may occur immediately upon extubation of the trachea. Moreover, edema formation occurs in two other phases of the postextubation period: Acutely during the first 5 to 20 minutes post extubation or on a delayed basis, within 30 minutes to 8 hours of extubation. Laryngeal edema may involve the supraglottic, retroarytenoidal, and subglottic areas. Severe respiratory obstruction may occur after extubation, and frequently requires urgent reintubation or tracheotomy. Steroid use in the treatment of laryngeal edema is controversial, but may reduce postextubation stridor, reduce the need for reintubation in select patients, and hasten the resolution of existing traumatic edema. Utilization of bilevel positive airway pressure (BiPAP) or heliox (helium–oxygen mixture) may also be of use in the postextubation patient with stridor.
Other causes of airway obstruction after extubation are blood clots, foreign bodies, dentures, traumatized dentition, and throat packs inadvertently left in the airway. Passive regurgitation or active vomiting at extubation may result in gastric content aspiration; stridor may be the presenting clinical sign if air movement is possible. Rapid deployment of therapy is imperative; nebulized racemic epinephrine, heliox, judicious use of anxiolytics, noninvasive positive pressure modalities, or tracheal intubation may be in order.
After Extubation
Complications after extubation are divided into early (up to 72 hours) and late (more than 72 hours).
Early Complications
Early complications are listed in Table 38.11. Mechanical irritation to the pharyngeal mucosa causes sore throat. Short-lived or prolonged aphonia—a weakened voice—is common, especially following prolonged intubation. Laryngeal incompetence following extubation is the rule; hence, resumption of an oral diet must be timed appropriately to the patient's ability to cough, control secretions, and competently and safely swallow liquids and solids.
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Table 38.11 Tracheal intubation complications seen after extubation |
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Vocal cord paralysis and arytenoid dislocation and dysfunction may be appreciated following extubation (198,199,200,201,202,203,204). Paralysis may be unilateral or bilateral, with the left cord twice as frequently affected as the right, and males predominating with this complication. Damage to the external laryngeal nerve may cause lasting voice change, with unilateral nerve injury usually causing hoarseness. Paralysis can result and, if the injury is bilateral, may lead to airway obstruction.
Late Complications
Late postextubation complications include laryngeal ulcer, granuloma, polyp, synechiae (fusion) of the vocal cords, laryngotracheal membrane webs, laryngeal or tracheal fibrosis, and nostril stricture from damage to the alae (202,203,205). Laryngeal ulcerations or granulomata are more commonly located at the posterior region of the vocal cords where the endotracheal tube tends to have more continual contact. The patient may complain of foreign body sensation, fullness or discomfort at the back of the throat, and persistent hoarseness. Any patient complaining of airway-related pain, discomfort, fever, or systemic signs of infection following difficult airway management should be evaluated for tissue injury in the upper and lower airway and pharyngoesophageal region (27,92).
Extubation of the Difficult Airway in the Intensive Care Unit
Airway management also constitutes maintaining control of the airway into the postextubation period. The known or suspected difficult airway patient should be evaluated in regard to factors that may contribute to his or her inability to tolerate extubation. A comprehensive review of medical and surgical conditions and previous airway interventions, an evaluation of the airway, and formulation of a primary plan for extubation as well as a rescue plan for intolerance are essential for optimizing safety (206,207,208). Reintubation, immediately or within 24 hours, may be required in up to 25% of ICU patients (209,210,211). Measures to avert reintubation such as noninvasive ventilation for those at highest risk for extubation failure are effective in preventing reintubation and may reduce mortality rate if done so upon extubation (212). However, a delay in the application of noninvasive ventilation when the patient displays signs of early or late postextubation respiratory distress or failure results in a less effective application in most patients, except those with COPD (213,214,215,216). Factors beyond routine extubation criteria that may be helpful in predicting failure include neurologic impairment, previous extubation failure, secretion control, and alterations in metabolic, renal, systemic, or cardiopulmonary issues (209,210,211).
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Table 38.12 Risk factors for difficult extubation |
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“Difficult extubation” is defined as the clinical situation when a patient presents with known or presumed risk factors that may contribute to difficulty re-establishing access to the airway (Table 38.12). The extubation of the patient with a known or presumed difficult airway and the potential for subsequent intolerance of the extubated state poses an increased risk to patient safety. An extubation strategy should be developed that allows the airway manager to (a) replace the ET in a timely manner and (b) ventilate and oxygenate the patient while he or she is being prepared for reintubation, as well as during the reintubation itself (30).
The practitioner should assess the patient's risk on two levels: The patient's predicted ability to tolerate the extubated state and the ability (or inability) to re-establish the airway if reintubation becomes necessary (206,207,208). Weaning criteria and extubation parameters will not be discussed as they vary by locale, practitioner, and the patient's clinical situation. Table 38.13 outlines two categories for pre-extubation evaluation (208).
NPO Status
The NPO status of the patient to be extubated and the subsequent need for reintubation has not been thoroughly studied, but it makes clinical sense to consider 2 to 4 hours off of distal enteral feeds prior to extubation while maintaining the NPO status post extubation until the patient appears at low risk for failing the extubation “trial.” Unfortunately, the ICU patient may succumb to reintubation based on a multitude of factors; hence, predictability of failure and when it will occur is difficult to discern.
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Table 38.13 The difficult extubation: Two categories for evaluation |
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The Cuff Leak
Hypopharyngeal narrowing from edema or redundant tissues, supraglottic edema, vocal cord swelling, and narrowing in the subglottic region of any etiology may contribute to the lack of a cuff leak (217,218,219,220,221,222). Too large of a tracheal tube in a small airway should, of course, be considered. A higher risk of post extubation stridor or the need for reintubation is prevalent in those without a cuff leak, in women, and in patients with a low Glasgow coma score (217,218,219,220,221,222). Attempting to determine the etiology for the lack of a cuff leak may impact patient care, as individuals may remain intubated longer than is required or receive an unneeded tracheostomy. If airway edema is the culprit, steps to decrease airway edema include elevation of the head, diuresis, steroid administration, minimizing further airway manipulation, and “time” (223,224,225). The cuff leak test as an indicator for predicting postextubation stridor is helpful, but the performance of a cuff leak test varies by institution and protocol, as does its interpretation by the individual physician. Testing to predict successful extubation is inconclusive (223,224,225). A relatively crude yet effective method of cuff leak test involves auscultation for cuff leak with or without a stethoscope. A more precise method is to take an indirect measurement of the volume of gas escaping around the ET following cuff deflation, determined by calculating the average difference between inspiratory and expiratory volume while on assisted ventilation (218,225). Cuff leak volume (CLV) may be measured as the difference of tidal volume delivered with and without cuff deflation and stated as a percentage of leak, or as an absolute volume. The percentage CLV will vary with the tidal volume administered during the test (8 mL/kg vs. 10–12 mL/kg), but several authors have found an absolute CLV less than 110 to 130 mL (218,219) or 10% to 24% of delivered tidal volume as helpful in predicting postextubation stridor (219,220,221,225). Stridor increases the risk of reintubation. Single- or multiple-dose steroids may reduce postextubation airway obstruction in pediatric patients, depending on dosing protocols, patient age, and duration of intubation (223). Steroid use in adults administered 6 hours prior to extubation—rather than 1 hour prior—may reduce postextubation stridor and decrease the need for reintubation in critically ill patients (210,223,224,225).
Risk Assessment: Direct Inspection of the Airway
Garnering useful information about the airway status may need to go well beyond the cuff leak test since it is relatively crude, provides little direct data regarding one's ability to access the airway in the event of a need for reintubation, and is relatively uninformative as to the actual status of the glottis. While it is mandatory that the records of the known difficult airway patient be reviewed, it is also the case that a record of previous airway interventions in a patient who may have undergone a marked alteration in their airway status could be less than informative. Practitioners should weigh the pros and cons of evaluating such an airway to determine ease or difficulty in the ability to gain access via conventional or advanced techniques. Additionally, some patients may need evaluation of their hypopharyngeal structures and supraglottic airway to assess airway patency and resolution of edema, swelling, and tissue injury. Conventional laryngoscopy is a standard choice for evaluation, but often fails due to a poor “line of sight.” Additionally, the relationship of grading and comparing the laryngeal view of a nonintubated to an intubated glottis is inconsistent (226). Flexible fiberoptic evaluation is useful but may be limited by secretions and edema (124). Video-laryngoscopy and other indirect visualization techniques that allow one to see “around the corner” are especially helpful. The Airtraq, as may other optical or video-laryngoscopy devices, has been found to be particularly useful by offering outstanding wide-angle visualization of the periglottic structures in the critically ill patient with a known difficult airway (144).
American Society of Anesthesiologists Practice Guidelines Statement Regarding Extubation of the Difficult Airway
The ASA guidelines (30) have suggested that a preformulated extubation strategy should include:
1. A consideration of the relative merits of awake extubation versus extubation before the return of consciousness; this is clearly more applicable to the operating room setting than to the ICU
2. An evaluation for general clinical factors that may produce an adverse impact on ventilation after the patient has been extubated
3. The formulation of an airway management plan that can be implemented if the patient is not able to maintain adequate ventilation after tracheal decannulation
4. Consideration of the short-term use of a device that can serve as a guide to facilitate intubation and/or provide a conduit for ventilation/oxygenation
Clinical Decision Plan for the Difficult Extubation
A variety of methods are available to assist the practitioner's ability to maintain continuous access to the airway following extubation, each with limitations and restrictions. Though no method guarantees control and the ability to re-secure the airway at all times, the LMA offers the ability for fiberoptic-assisted visualization of the supraglottic structures while serving as a ventilating and reintubating conduit; it is hampered by a limited time frame in which it may be left in place. The bronchoscope is useful for periglottic assessment following extubation, but requires advanced skills and minimal secretions. Moreover, it offers only a brief moment for airway assessment and access to the airway following extubation (124). Conversely, the airway exchange catheter (AEC, Fig. 38.14) allows continuous control of the airway after extubation, is well tolerated in most patients, and serves as an adjunct for reintubation and oxygen administration (206,227,228,229). Patient intolerance, accidental dislodgment, and mucosal and tracheobronchial wall injury have been reported, but are rare (230,231,232,233,234). Carinal irritation may be treated with proximal repositioning, the instillation of topical agents to anesthetize the airway, and explanation and reassurance. Dislodgment may occur, resultant from an uncooperative patient or a poorly secured catheter. Observation in a monitored environment with experienced personnel should be given top priority, as should the immediate availability of difficult airway equipment in the event of intolerance to tracheal decannulation (206,207,208). Tips for success with the use of this device are shown in Table 38.14.
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Table 38.14 Airway exchange catheter (AEC)-assisted extubation: Tips for success |
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Clinical judgment and the patient's cardiopulmonary and other systemic conditions, combined with the airway status, should guide the clinician in establishing a reasonable time period for maintaining a state of “reversible extubation” with the indwelling AEC (Table 38.15) (206).
Exchanging an Endotracheal Tube
Exchanging an ET due to cuff rupture, occlusion, damage, kinking, a change in surgical or postoperative plans, or self-extubation masquerading as a cuff leak, or when the requesting team prefers a different size or alteration in location, is a common procedure. Preparation for the possible failure of the exchange technique and appreciation of the potential complications is imperative (30).
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Table 38.15 Suggested guidelines for maintaining presence of airway exchange catheter |
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Four methods typify the airway manager's armamentarium of exchanging an ET: Direct laryngoscopy, a flexible or rigid fiberscope, the airway exchange catheter, or a combination of these techniques (2). Proper preparation is imperative and patients should undergo a comprehensive airway exam. Access to a variety of airway rescue devices is of paramount importance in the event of difficulty with ET exchange (208).
Direct Laryngoscopy
DL is the most common and easiest technique for exchanging an ET, but has several pitfalls and limitations. Airway collapse following removal of the ET may impede visualization and, thus, reintubation. This method leaves the patient without continuous access to the airway and should be restricted to the uncomplicated “easy” airway (94).
Fiberscopic Bronchoscope–assisted Exchange
Fiberscopic bronchoscope–assisted exchange (FBAE) is useful for nasal to oral or vice versa exchanges and oral-to-oral exchanges, as well as for immediate confirmation of ET placement within the trachea and positioning precision (3,4,5). Though difficult in the edematous or secretion-filled airway, FBAE allows continuous airway access in skilled hands. Passing the flexible fiberscope through the glottis along the side of the existing ET, although not without significant difficulty, the old ET can be backed out, followed by advancing the ET—preloaded onto the fiberoptic bronchoscope—into the trachea. Conversely, the preloaded flexible fiberscope may be placed immediately adjacent to the glottis. The old ET is then backed out over an AEC and the glottis is intubated with the FOB-ET complex. A larger flexible model is better maneuvered than a pediatric-sized scope. Passing a lubricated, warmed ET that is rotated 90 degrees will reduce arytenoid-glottic impingement. Rigid fiberscopes such as the Bullard, the Wu scope, the Upsher, and the Airtraq are very useful for visualizing the otherwise difficult airway during the exchange by offering the ability to “see around the corner” (124,235,236,237,238). The fiberscope may be rendered useless by unrecognizable airway landmarks, edema, and secretions as well as operator inexperience.
Airway Exchange Catheter
The AEC incorporates the Seldinger technique for maintaining continuous access to the airway. Strategy and preparation are the keys to successful and safe exchange (Table 38.16). Proper sizing of the AEC to best approximate the inner diameter of the ET will allow a smoother replacement. A chin lift–jaw thrust maneuver and/or laryngoscopy will assist the passing of a well-lubricated warmed ET that may need to be rotated counterclockwise by 90 degrees to reduce glottic impingement. A larger-diameter (19 French is the size we most often use) AEC is best in passing an adult-sized ET. Exchanging a tracheostomy tube over an AEC is especially valuable when the peristomal tissues are immature. The use of a tracheal hook to elevate the tracheal cartilage and proper head/neck positioning (shoulder roll) will optimize the exchange. The exchange is often performed “blindly” since laryngoscopy in the ICU patient often reveals little to no view of the supraglottic airway. Thus, incorporation of any of the advanced laryngoscopes that assist in “seeing around the corner” (Bullard, Wu, Glidescope, McGrath, Airtraq, etc.) offer certain advantages to the operator and the patient: (a) assessment of the airway is improved; (b) there is better estimation of what size ET the glottis will accept; (c) visualization during the exchange offers the ability to direct the new ET into the trachea and reduce arytenoid hang-up or impingement; (d) it confirms that the AEC remains in the trachea during the exchange; and (e) it allows visual confirmation that the ET is placed in the trachea and the ET cuff is lowered below the glottis. Finally, the advanced airway device would be in position to assist in reintubation if any unforeseen difficulties arise during the exchange.
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Table 38.16 Strategy and preparation for endotracheal tube (ET) exchange |
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Minimizing the gap between the ET and the AEC is important for ease of exchange. If, due to luminal size restrictions, the smaller-sized AEC (4 mm, 11 French) is used when going from, for example, a double-lumen to a single-lumen ET in a high-risk ICU patient, then temporary reintubation with a smaller warmed (6.5 mm) ET as opposed to a larger (8–9 mm) ET may ease passage into the trachea. Once secured, a larger AEC may be passed via the indwelling ET with subsequent exchange to a larger ET. Various AEC exchange techniques are practiced, and customized variations of the standard methods assist the practitioner to tackle individual patient characteristics (94,235,236,237,238).
ET exchange, while simple conceptually, is not a simple procedure as hypoxemia, esophageal intubation, and loss of the airway may occur. The decision on the method of exchange is based on known or suspected airway difficulty, edema and secretions, and most significantly, the experience and judgment of the clinician. It is recommended that continuous airway access be maintained in all but the simplest and most straightforward airway situations (94).
Follow-up Care
Following a life-threatening airway encounter with a patient, dissemination of such information is often overlooked and there is currently no standard method of relaying information from one caregiver to another (30,89). Notes written in the chart are a start, as is a discernible or highly visible label on the outside of the medical chart, but these may be inadequate. Informative and accurate medical records of airway interventions should be promoted as a potentially life-saving exercise; hence, detailed accounting of an intubation with more information written in the chart—not less—is best for patient care. However, a caveat to note is as follows:
If the chart states difficulty was encountered, assume it will again be difficult; if the notes states it was “easy” or no details are provided, assume and plan on the potential for difficulty.
Discussing difficulties with the patient in this setting is certainly different from the elective surgical case in the operating room. For the future care of the patient, opening a Medic Alert file has many advantages for improved dissemination of patient care information, especially in our mobile society. Obtaining medical records in a timely fashion is a constant deterrent. However, the Medic Alert file will not assist the care for the current hospitalization, only in future ones (27,30,89). Hence, steps for the current hospitalization can be taken to improve communication for efficient transfer of needed information to the airway team. Initially identifying the patient by a colorful wrist bracelet, analogous to a medication or latex allergy bracelet, is a simple but effective trigger for the airway team to investigate the patient's airway status. A computerized medical record may allow a “Difficult Airway Alert” to be readily and prominently displayed, thus allowing identification of the patient on the current and possibly future hospitalizations—although only at the current hospital. Future airway interventions in the unrecognizable or unanticipated difficult airway are particularly benefited by “flagging” the patient. The Medic Alert system is dependent on patient compliance and payment.
References
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