Robert C. Luten
Niranjan Kissoon
Technique
Securing an airway in a patient, adult or child, is made more challenging or difficult for two principal reasons:
1. The patient's normal airway anatomy is modified because of an acute insult
2. The patient with an abnormal airway (e.g., a congenital anomaly) requires airway management for an unrelated cause, such as respiratory failure due to an asthma exacerbation
The approach to the emergent difficult airway is described in Chapter 7, which should be read before this chapter. Pediatric difficult airways, especially those encountered in emergency situations, are far less common than in adults, not well studied, and not extensively covered in any textbook. For purposes of this discussion, difficult pediatric airways are divided functionally into difficult airways secondary to:
1. Acute infectious disease
2. Acute noninfectious disease
3. Congenital anomalies, most commonly with a superimposed indication for emergency airway management unrelated to the airway abnormality (e.g., respiratory failure secondary to asthma or pneumonia)
Difficult Airways Secondary to Acute Infectious Disease
Examples of entities in which an otherwise normal anatomy is altered by an infectious process include
1. Epiglottitis
2. Croup (usually not a difficult intubation; Table 22-1)
3. Retropharyngeal abscess
4. Bacterial tracheitis
5. Ludwig's angina
Most often, children with the disorders described in this and in the next section present because the normal anatomy is altered, usually by swelling, which leads to varying degrees of airway obstruction. The pediatric patient is especially susceptible to airway obstruction from swelling, often from conditions that are less threatening to the adult. This is illustrated in Table 22-2, which outlines the effect of 1-mm of edema on airway resistance in the infant (4-mm airway diameter) versus adult (8-mm airway diameter). These figures reflect the quietly breathing infant or adult. If the child cries, the work of breathing is increased 32-fold, hence the principle of maintaining children in a quiet, nonthreatening, and comfortable environment during evaluation and in preparation for management.
Table 22-1 outlines the two most notorious infectious diseases involving the upper airway with potential for obstruction in children, epiglottitis and croup. Epiglottitis is rarely seen in the Western world since the introduction of the Haemophilus influenza vaccine, and croup, commonly referred to in the differential diagnosis of epiglottitis, is usually a clinically distinct entity that is rarely a difficult intubation because the obstruction is subglottic. It is of value still to discuss epiglottitis because it represents the prototype indication for needle cricothyrotomy (see Chapter 21) as an obstruction proximal to the glottic opening when bag-mask ventilation (BMV) and intubation fail. Other, noninfectious problems causing obstruction proximal to the glottic opening include facial trauma, angioedema, and caustic ingestions and burns involving the hypopharynx. To put these “most-feared” diseases in perspective, the following points should be kept in mind:
A. These problems have in common the fact that airway intervention in the emergency department (ED) should never be attempted unless deterioration occurs or is imminent. If one adheres to this principle and then follows a stepwise approach as outlined in Table 22-1, results will be optimal and complications, especially iatrogenic complications, will be avoided.
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Table 22.1 Management of The “Most-Feared” Pediatric Airway Problems |
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Table 22.2 Effect of 1-mm Edema on Airway Resistance |
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B. Epiglottitis and croup are distinct clinical entities, that rarely, if ever, require radiologic studies to distinguish the two. The fact that textbooks group them together in the differential diagnosis of acute life-threatening upper airway obstruction is misleading because the differentiation is usually clinically obvious.
C. Croup, as opposed to epiglottitis or foreign body aspiration, will respond to medical intervention (inhaled epinephrine), which usually obviates the need for intubation.
D. Retropharyngeal abscess in children usually presents without airway compromise, although it is virtually always found in textbooks in the differential diagnosis of acute life-threatening airway obstruction. The same is true of Ludwig's angina, an even less common disease. The term para-airway diagnoses is used to describe conditions involving the airway above the level of the glottis. These conditions rarely require emergency airway intervention of the pediatric patient in the ED. A retropharyngeal abscess most commonly presents with odynophagia and neck stiffness. Lateral neck films reveal thickening of the retropharyngeal space. Most of these patients have retropharyngeal cellulitis and respond to antibiotics. If an abscess is present, incision and drainage is required, but rarely, if ever, is it necessary to actively manage the airway in the ED.
Difficult Airways Secondary to Noninfectious Causes
1. Foreign body
2. Burns
3. Anaphylaxis
4. Caustic ingestion
5. Trauma
6. Other swellings (angioedema, Quinke disease, etc.)
Foreign body aspiration is probably the most feared pediatric airway problem. They should be managed “expectantly,” meaning that no intervention should be attempted in the ED and that resources should be summoned to provide definitive care (removal) in the operating room setting. If the patient converts to complete obstruction, immediate intervention is required. With complete obstruction of the airway, oxygen desaturation, rendering the patient unconscious, ordinarily occurs within 1 minute or so. A stepwise approach should be followed.
A. The conscious child
Although controversy exists regarding the ideal emergency procedure for relief of choking, the Heimlich maneuver is suggested by the American Heart Association for children older than 1 year. For children younger than 1 year, a series of five back blows followed by five chest thrusts is recommended.
If the patient is conscious, the correct initial treatment is the application of these maneuvers, which should be repeated until the foreign body is expelled or the patient loses consciousness. To summarize
· Children younger than 1 year: five back blows followed by five chest thrusts.
· Children older than 1 year: repetitive abdominal thrusts.
· Attempt ventilation.
· Continue this sequence as long as the child is conscious.
Attempting instrumentation to remove the foreign body of a completely obstructed upper airway while the patient is still conscious is not wise. If the maneuvers are successful in removing the foreign body, and the patient can phonate and breathe normally, an observation period of 12 to 24 hours is advised.
The disposition of a child with a stable partial obstruction to the operating room as described previously may not be possible if expert resources are unavailable or unwilling, and an alternative plan, preferably crafted in advance as time is of the essence, must be activated. Removal of the foreign body in the ED should only be done if other options are unavailable. The approach to the partially obstructed airway is described elsewhere (see Chapter 36).
Recognizing that conscious children are unlikely to cooperate with efforts to remove the foreign body sedation is important. As described in the Tips and Pearls section of Chapter 30, the intravenous titration of ketamine beginning at the induction dose (1–2 mg/kg), or 4 mg/kg intramuscularly, produces dependable deep sedation/anesthesia while maintaining respiratory drive and reflexes.
B. The unconscious child
If the maneuvers are unsuccessful in removing the foreign body and the patient loses consciousness, or if the patient with an upper airway foreign body presents unconscious, direct laryngoscopy should be attempted. This is a “crash airway” (see Chapter 2), and the administration of a neuromuscular blocking agent is not indicated for the initial attempt. However, if the child presents with clenched teeth or other signs of substantial muscle activity, use of succinylcholine to achieve relaxation in order to identify and remove the foreign body may be necessary. If the foreign body can be identified under direct laryngoscopy, it should be removed.
Occasionally, BMV using high pressure (usually a two-person, two-handed technique is required to achieve an adequate seal) may be successful. If ventilation is successful in these cases, it is usually because the foreign body has been forced beyond the glottis and subglottic region into one of the mainstem bronchi.
If BMV is unsuccessful, the child should be intubated and an attempt made to advance the foreign body into either mainstem bronchus. The tube should then be withdrawn above the carina and ventilation of the unobstructed lung attempted. Resuscitation guides such as the Broselow-Luten tape provide a “lip-to-tip” distance number as an objective guide for positioning the endotracheal tube (ETT) in the trachea of a child. With the ETT positioned at the stipulated distance at the lip, the distal opening of the ETT is halfway between the vocal cords and the carina, although clinical verification is always recommended. Occasionally, soft foreign bodies such as foodstuff or adenoidal tissue, if a nasal intubation was performed, may lodge within the ETT, necessitating withdrawal of the ETT. In the event that the patient breathes spontaneously following this maneuver, BMV or intubation may not be required.
Percutaneous approaches (e.g., needle cricothyrotomy) are rarely indicated in foreign body aspirations, and will only be successful if the foreign body is lodged in the airway above the entrance of the needle into the airway (e.g., a ball bearing seen to be lodged below the vocal cords at the cricoid ring on laryngoscopy that cannot be extracted with instruments). In the event that the foreign body cannot be visualized on direct laryngoscopy, it is unlikely that a percutaneous approach will be distal to the object, rendering the procedure ineffective. An overview of the sequence is presented in Table 22-1, and detail is provided in Figure 22-1.
In both adults and children, if the foreign body becomes lodged causing complete obstruction and cannot be retrieved or expelled by blind maneuvers, attempts at BMV followed by advancement of the foreign body into a mainstem bronchus as described previously should be immediately performed.
C. Timing the intervention
As is the case for adults, the anticipated clinical course of the presenting condition becomes a key determinant in the decision whether to actively intervene in the airway (e.g., intubate) or to observe the patient for possible deterioration. Table 22-3 groups disorders from both infectious and noninfectious causes according to timing of intervention based on anticipated clinical course.
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Figure 22-1 • Stepwise approach for the management of an aspirated foreign body. |
The expectant intervention group represents patients in whom the intervention itself may be more hazardous than a period of close observation, during which preparation is rapidly undertaken for definitive management. In these children, the airway should be actively managed in the ED only if deterioration occurs. The rationale in these cases is that intervention is best done in a controlled environment by a multidisciplinary team with expertise in the management of difficult airways. Treatment in less than ideal conditions may lead to untoward outcomes.
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Table 22.3 Timing of Intervention According to Anticipated Clinical Course |
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The signs and symptoms of impending airway obstruction in children are important indicators that guide the approach to the early intervention group. These disorders, if left to expectant treatment, have a greater potential for deterioration. An example is the burn or caustic ingestion patient who is beginning to develop a raspy voice. This symptom heralds the potential for deterioration, although the degree and pace of progression cannot be predicted. However, it must be assumed that progression to the point of obstruction is possible, in which case should intubation become necessary, it will be extremely difficult if not impossible. For this reason, intervention earlier rather than later is recommended. Patients with compromised airways secondary to anaphylactic or anaphylactoid reactions (e.g., angioedema) who do not respond to immediate medical treatment similarly require early intervention to prevent a more difficult, unmanageable problem later.
As discussed previously, children are anatomically less able to accommodate airway swelling than adults and can deteriorate precipitously.
Difficult Airways Secondary to Congenital Anomalies
Patients with difficult airways secondary to congenital anomalies receive the most attention in discussions of difficult airways in pediatrics. However, they are encountered only rarely in the ED, much less frequently than groups 1 and 2. Also, the literature concerning these patients usually describes elective situations, managed by experienced pediatric anesthesiology subspecialists in well-equipped operating rooms with the intubation done under controlled conditions. This kind of discussion is not relevant to the management of the airway if these children present emergently.
Most patients with congenital anomalies presenting to the ED require intubation for reasons unrelated to their difficult airway (e.g., a child with Pierre Robin syndrome with respiratory failure secondary to asthma). The best approach for these patients is to obtain expert subspecialty assistance as early as possible and, as with all patients, to aggressively manage the medical condition to try to obviate the need for intubation. Unlike the conditions discussed previously in this chapter, there is some luxury of time here because those factors that progressively increase the likelihood of being confronted with a difficult airway are not operative. Delay in managing the airway may result in some deterioration of the patient, but will not make the airway itself any more difficult, except possibly by limiting the time available to successfully intubate a severely hypoxemic child.
The micrognathic mandible is the most common anatomical feature in the child rendering intubation difficult, although there are others. The small mandible reduces the space (“mandibular space”) into which the tongue and submandibular tissue must be compressed with the laryngoscope blade to visualize the glottic opening. A significantly recessed (micrognathic) mandible can be recognized by drawing a line that touches the forehead and maxilla and continues inferiorly (Fig. 22-2). In a patient with grossly normal anatomy, the line also touches the tip of the chin. In the micrognathic patient, a gap between the line and the tip of the chin is observed. In such patients, as described in the Difficult Airway Algorithm, an awake look (sedated) to assess the degree to which the tongue can be displaced into the mandibular space may be attempted before opting for rapid sequence intubation (RSI).
For patients in extremis or in crash situations, the clinician is left with no other options than those used in other patients. Often, such simple procedures as BMV or endotracheal intubation are successful in these patients and should remain as the mainstay of therapy.
Therapeutic options for the pediatric difficult airway are outlined in Table 22-4.
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Figure 22-2 • It may not always be obvious that a given patient possesses a difficult airway (A). When compared with a normal child, the differences may be more striking (A vs. B). In the individual patient, however, a line drawn inferiorly from the forehead, touching the maxilla, will also touch the mandible (D). The failure to do so demonstrates a degree of micrognathia (C), which must be correlated with the clinical picture. Source: Extrapolated from Frankville D. ASA refresher course. Parkridge, IL: American Society of Anesthesiologists; 2001:126. |
Evidence
Unfortunately, little evidence is published on the recognition and management of the difficult pediatric airway in an emergency. Most of the descriptions of difficult pediatric airways deal with children with congenital anomalies. The literature on predicting the difficulty airway employing a systematic clinical evaluation is confined to adults and may not necessarily be applicable to children (1; Table 22-5). It is anticipated that the National Emergency Airway Registry project will enable the characterization of the scope of the difficult airway in pediatrics and provide “best practice” approaches to its management.
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Table 22.4 Therapeutic Options for The Difficult Airway |
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1. Heimlich maneuver. There is a controversy in the literature as to the ideal emergency procedure for relief of choking due to foreign body aspiration (2,3). However, the Heimlich maneuver is suggested by the American Heart Association as the maneuver to be tried initially for children older than 1 year. In children younger than 1 year, the danger of intra-abdominal injury precludes its use, and a combination of back blows and chest thrusts is recommended (4). Although little evidence exists, it is recommended that if obstruction is incomplete and the patient is phonating, then no intervention should be attempted. This approach is predicated on the fact that the force of a cough generates five to six times the airflow velocity of other maneuvers and is more likely to expel the foreign body. Moreover, there is concern that these interventions may have the potential to convert a partial obstruction to a total obstruction.
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Table 22.5 A Sample Comparison of Pediatric and Adult Risk Factors |
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References
1. Kopp VJ, Bailey A, Calhoun PE, et al. Utility of the Mallampati classification for predicting difficult intubation in pediatric patients. Anesthesiology 1995;83:3A1147.
2. Redding JS. The choking controversy: critique of evidence on the Heimlich maneuver. Crit Care Med 1979;7:475–479.
3. Heimlich HJ. First aid for choking children: back blows and chest thrusts cause complications and death. Pediatrics 1982;70:120–125.
4. Zaritsky A, Nadkarni V, Hickey R, et al., eds. PALS Provider Manual. Dallas, TX: American Heart Association; 2002.
