Patrick A. Nee
Diane M. Birnbaumer
The Clinical Challenge
People age 65 and older now represent about 15% of the population. The number of retirees in the United States will reach 52 million by 2020. Those age 85 years and older will number 7 million by that year and increase to 14 million by 2040. Elderly patients present disproportionately frequently to the emergency services. A recent U.S. study identified increasing numbers of very old patients requiring urgent airway interventions in the emergency department (ED). Chronic obstructive pulmonary disease (COPD), cardiogenic shock, and severe sepsis are predominantly diseases of older age. Table 34-1 shows the ten most frequent diagnoses in ED patients (older than 65 years) who were intubated in a UK general hospital.
Aging is characterised by a progressive, irreversible deterioration in physiological reserve.
Advanced age affects airway management decision making in three primary areas.
A. Respiratory Reserve
Age-related changes in the lungs impair gas exchange, reducing oxygen tension at baseline. The normal PaO2 falls by 4 mm Hg per decade after the age of 20 years and may be calculated by the formula 100 - (age/4) mm Hg or 13.3 - (age/30) kPa. Reduced sensitivity of central respiratory drive, weakened respiratory muscles, and altered chest wall mechanics reduce the ability of the older adult to respond to hypoxia and hypercarbia. Consequently, oxygen saturation may fall rapidly in the face of a respiratory threat. Impaired airway reflexes, swallowing disorders, drug effects, and delayed gastric emptying may worsen the situation because of increased risk of pulmonary aspiration. Finally, the presence of cardiovascular or cerebrovascular disease reduces the patient's tolerance of hypoxemia.
B. High incidence of difficult airway
Elderly patients have a relatively high incidence of difficult airways, necessitating early planning of the approach and contingencies in case of failure to intubate.
C. Ethical Considerations
Advanced age should not be a contraindication to advanced airway interventions, but the patient's desires, advance directives, and comorbidities must be considered. Poor outcomes relate to functional limitation and comorbidities rather than chronological age.
Continuous positive airway pressure and bilevel positive airway pressure are often used in elderly patients with respiratory failure, in whom invasive ventilation is deemed inappropriate. Life-sustaining interventions, including intubation, may not be appropriate (or desired) in all cases. The principle of autonomy determines that a patient's views on treatment and treatment limitation must be respected. However, communication with sick, elderly patients in the ED setting may be difficult, especially in those with cognitive dysfunction.
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TABLE 34-1 Most Common Diagnoses in Patients (older than 65 years) Intubated in the Emergency Department |
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Approach to the Airway
In view of their poor tolerance of hypoxia, elderly patients may be considered for intubation at an earlier point in the course of an airway or respiratory emergency. Rapid sequence intubation (RSI) is the procedure of choice and may be appropriate even in patients with clinical features suggesting difficulty. Advanced age may be attended by poor mouth opening, carious or missing teeth, stiff lungs, and reduced cervical range of motion.
Preoxygenation is critically important; older patients desaturate relatively quickly due to age-associated changes in the lungs and pre-existing heart and lung disease. For the same reasons, preoxygenation may not be completely effective. Oxygen saturation must be monitored meticulously, and bag-mask ventilation (BMV) with high-flow oxygen must be instituted if saturation falls below 90%. Mask seal may be problematic because of facial wasting, and a two-handed, two-person technique, with a nasal or oral airway, may be required. Well-fitting dentures should be left in place during BMV and removed for intubation. Mouth opening may be limited by temporomandibular joint arthrosis, and cervical spondylosis may restrict neck flexion and head extension. Loss of elastic tissues promotes collapse of the upper airways and partial obstruction. Reduced lung compliance and chest wall stiffness may make BMV, and ventilation with an extraglottic device difficult. This situation is made worse by coexisting COPD or heart failure.
Anticipating a difficult intubation, the physician must attempt to optimize all six components of the best attempt (see Chapter 6) before proceeding. Alternative airway approaches, such as fiberoptic intubation, may be considered at the outset, or if difficulty is encountered. Blind nasotracheal intubation is a poor choice in older subjects due to increased risk of pharyngeal perforation and bleeding.
Surgical cricothyrotomy is the appropriate choice in a “can't intubate, can't oxygenate” failed airway situation, but abnormal airway anatomy, past radiation therapy or surgery, and relatively inelastic tissues increase the challenge.
Drug Dosage and Administration
A. Pretreatment
The pretreatment agents for older adults are the same as for others: lidocaine and fentanyl. These are used according to the “ABC” mnemonic in Chapter 3. Lidocaine is recommended for elderly patients with elevated intracranial pressure or reactive airways disease, and does not require dose adjustment. Fentanyl mitigates catecholamine response to laryngeal manipulation, which can be particularly important in the elderly who have a high incidence of cardiovascular and cerebrovascular disease. Although senescence blunts these autonomic responses to some extent, critically ill hypoxic and acidotic older patients remain at risk of stroke, myocardial infarction, aortic dissection, or rupture of an abdominal aortic aneurysm.
Attenuation of these responses is not without risk. Older patients are more sensitive to the respiratory depressant and hypotensive effects of opioids. Consequently, fentanyl should be given more slowly (over 2–3 minutes) and in smaller doses (1–2 µg/kg) in the elderly.
B. Paralysis with induction
Etomidate is the preferred agent in older patients because of its superior hemodynamic stability. Etomidate will not blunt the pressor response to laryngoscopy, and fentanyl pretreatment is indicated. The controversy regarding etomidate in shock and its effects on adrenal function are addressed in Chapter 18.
Thiopental can cause significant hypotension in the elderly, and, if used, the dose should be reduced to 1.5 or 1 mg/kg, even in euvolemic, normotensive patients. Similarly, propofol can be used, with the dose reduced to 1 mg/kg or even lower. Ketamine causes less cardiovascular lability and is useful in reactive airways disease. However, its sympathomimetic properties are a disadvantage in patients with ischemic heart disease, cerebrovascular disease, elevated intracranial pressure, or Parkinson disease.
Succinylcholine is the paralytic agent of choice for RSI in the elderly, but older patients are more likely to have conditions that can predispose to succinylcholine-induced hyperkalemia, especially stroke. Recent denervating stroke (occurring 3 days to 6 months before the succinylcholine is given) is associated with a risk of hyperkalemia. When there is any uncertainty regarding precisely when the stroke occurred, use of an alternative paralytic agent, such as rocuronium or vecuronium, is advised. In chronic renal failure, absent other risk factors, succinylcholine is safe.
Postintubation Management
The principles of postintubation management set out in Chapter 3 are appropriate to the aging adult. Sedatives (midazolam, propofol) and analgesics (morphine, fentanyl, alfentanil) should be given at reduced doses, and titrated to response, to minimize adverse effects (“start low, go slow”). Neuromuscular blocking agents are rarely necessary and, if used, should also be given in reduced doses and with increased intervals between doses. Ventilator settings are not usually affected by age, but decreased chest wall and pulmonary compliance may elevate ventilation pressures. In COPD, it is advisable to limit peak pressure and allow a prolonged expiratory phase. Positive-pressure ventilation, particularly with high levels of positive end-expiratory pressure, can unmask relative hypovolemia and may exacerbate the hypotensive effects of sedative drugs. Pressure-controlled ventilation is the preferred mode.
Tips and Pearls
RSI is the procedure of choice, but the physician must anticipate difficulty and prepare for alternative approaches. Elderly patients desaturate quickly, and preoxygenation is important. Interposed breaths may be required after induction. Age-related cardiovascular changes, pre-existing disease, and drug interactions enhance the hypotensive response to induction, and reduced doses of sedatives and hypnotics should be used. Reduced cardiac output prolongs the arm-brain circulation time, and a delayed onset of action should be expected for all intravenous drugs. Pretreatment is as for younger patients. Rocuronium may be substituted where there are contraindications to succinylcholine. Finally, where there is incomplete information in respect of the patient's views on treatment limitation, it is advisable to proceed with interventions.
Evidence
1. Is older age an independent predictor of difficult intubation? Airway morphology may be adversely affected by age. Turkish investigators found the greatest reduction in thyromental and sternomental distances, as well as reduced Mallampati class and cervical range of movement, in patients ages 50 to 70 years (1). In contrast, in a Scottish ED-based study of 156 intubations, there was no relationship between mean age and (Cormack-Lehane) grade at intubation (2).
Independent covariates associated with difficulty in intubation were derived in two sizeable prehospital studies. Age was not independently associated with intubation difficulty in either population (3,4).
Injury during tracheal intubation is more common in the elderly. A North American group found an almost threefold increase in the risk of pharyngoesophageal perforation in patients older than 60 years (5). Of 203 dental injuries reported in Israeli hospitals over a 7-year period, the majority were sustained in patients ages 50 to 70 years (6).
2. Which pretreatment drugs should be used in the elderly? There is no specific evidence regarding the use of lidocaine in older adults with reactive airways disease or increased intracranial pressure in the emergency setting. Pending confirmatory evidence, we recommend that the elderly be considered for pretreatment agents (lidocaine, fentanyl) as for their younger counterparts. Although fentanyl is most familiar to emergency physicians, theoretically, shorter-acting opioids may offer advantage in the elderly. Alfentanil and remifentanil attenuated the pressor response to laryngoscopy and intubation in 40 elective surgical patients older than 65 years. However, adverse effects were common; in fact, hypotension was noted in three and four patients, respectively (7). Opioids onset more slowly in older subjects, and their effects persist longer, compared with younger age groups. The elderly are more sensitive to the respiratory and cardiovascular effects of these drugs and a 30% to 50% dose reduction is required (8,9).
3. Which induction agent (and what dose) should be used in the elderly? Options for intravenous induction in the elderly include etomidate, midazolam, propofol, and thiopental. Observational studies have shown that the plasma concentration required to induce the (desired and undesired) effects of these agents is up to 50% less in older subjects. Clinical effects take longer to become apparent and persist longer. A 40% reduction in dose of propofol, midazolam, or thiopental sodium is recommended in patients older than 65 years (9,10).
Etomidate (0.3 mg/kg) was used as the induction agent in 522 intubations in a Canadian hospital during a 42-month period. Sedation (and paralysis with succinylcholine) was deemed to be excellent in 88% of intubations. There was a high incidence of technical facility and a low rate of complications, with clinically insignificant elevations in heart rate and blood pressure, not related to age. Cardiac arrest occurred within 15 minutes of intubation in 17 patients, 10 of whom were older adults. In these cases, cardiac and cerebrovascular disease predominated as indications for the procedure, and the induction agent was not implicated in the outcome (11).
In a study of 160 cases from Hong Kong, midazolam caused significantly more hypotension than etomidate, particularly in patients with age older than 70 years (12). Similar advantage was found for etomidate compared to propofol when used for procedural sedation in the critically ill ED patients (13). A recent review of the literature on the use of etomidate in the ED setting concluded that the drug was effective and appropriate, even in hypovolemic patients and those with limited cardiac reserve (14). Dose reduction of etomidate in adults undergoing elective procedures has been described without loss of effect. However, evidence is lacking in the emergency situation, and 0.3 mg/kg continues to be recommended (15).
4. Which muscle relaxant (and what dose) should be used in RSI in the elderly? The advantages of succinylcholine in RSI are set out in Chapter 19. Many of the adverse effects are germane to the elderly patient and consideration is as for nonelderly adults. A reduced dose of succinylcholine (0.6 mg/kg) produced acceptable intubating conditions in elective surgical patients, with shortened neuromuscular recovery time (16,17), but data specific to the elderly are lacking, and we recommend that the standard RSI dose of 1.5 mg/kg be used for emergency intubation of all patients, regardless of whether they are elderly (15).
References
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