Rosen’s Emergency Medicine: Concepts and Clinical Practice, Sixth Edition, 3 volume set

Book Preface

Airway management is a defining element for the specialty of emergency medicine. Although practitioners from other specialties often have knowledge and skills that overlap those of the emergency physician, the ability to provide critical care and definitive airway management for all patients, regardless of the cause of their presentation, is unique to the specialty of emergency medicine. The emergency physician has primary responsibility for management of the airway. All techniques of airway management lie within the domain of emergency medicine. Rapid sequence intubation (RSI) is the cornerstone, but emergency airway management includes various intubation maneuvers, use of ancillary devices, approaches to the difficult airway, and rescue techniques when intubation fails.

Since the first reported use of neuromuscular blocking agents (NMBAs) in the emergency department by emergency personnel in 1971, there has been progressive sophistication of emergency airway techniques, pharmacologic agents, and special devices used to facilitate intubation.^[] The American College of Emergency Physicians stated in its policy on RSI that the use of NMBAs to facilitate tracheal intubation is within the domain of emergency medicine and that emergency physicians should possess the necessary knowledge, experience, and training to apply RSI in the clinical care of patients.^[4] In the 1990s, widespread adoption of RSI as the method of choice for most emergency intubations in the emergency department occurred, and increasing attention has been focused on identification and management of patients with anticipated difficult intubation.^[]

PATHOPHYSIOLOGY Decision to Intubate

A decision to intubate should be based on careful patient assessment with respect to three essential criteria: (1) failure to maintain or protect the airway, (2) failure of ventilation or oxygenation, and (3) the patient’s anticipated clinical course and likelihood of deterioration.^[7]

Failure to Maintain or Protect the Airway

A patent airway is essential for adequate ventilation and oxygenation. If the patient is unable to maintain the airway, patency must be established by artificial means, such as repositioning, chin lift, jaw thrust, or insertion of an oral or nasal airway. Likewise, the patient must be able to protect against aspiration of gastric contents, which carries significant morbidity and mortality. Traditionally, presence or absence of a gag reflex has been advocated as a reliable indicator of the patient’s ability to protect the airway, but the gag reflex is absent in 12% to 25% of normal adults, and there is no evidence that its presence or absence corresponds to airway protective reflexes or the need for intubation.^[] A more reliable indicator may be the patient’s ability to swallow or handle secretions, but this also remains to be tested. The recommended approach is to evaluate the patient’s ability to phonate (which provides information about level of consciousness and voice quality), level of consciousness, and ability to manage his or her own secretions (e.g., pooling of secretions in the oropharynx, absence of swallowing spontaneously or to command.) In general, a patient who requires a maneuver to establish a patent airway or who easily tolerates an oral airway probably requires intubation for protection of that airway, unless a temporary or readily reversible condition, such as opioid overdose, is present.

Failure of Ventilation or Oxygenation

Ventilatory failure that is not reversible by clinical means or increasing hypoxemia that is not adequately responsive to supplemental oxygen is a primary indication for intubation. This assessment is clinical and includes evaluation of the patient’s general status, oxygenation by pulse oximetry, and changes in the ventilatory pattern. Continuous capnography also can be helpful, but is not essential when oximetry readings are reliable. Arterial blood gases (ABGs) generally are not required to make a determination regarding the patient’s need for intubation. In most circumstances, clinical assessment, including pulse oximetry, and observation of improvement or deterioration lead to a correct decision. ABGs are rarely helpful, and may be misleading, so, if obtained, they must be interpreted carefully in the context of the patient’s clinical status. Patients who are clinically stable or improving despite severe ABG alterations may not require intubation, whereas a rapidly tiring patient may require intubation when ABG values are only modestly disturbed or even improving.

Regardless of the underlying cause, the need for mechanical ventilation generally mandates intubation. External mask devices increasingly have been used to provide assisted mechanical ventilation without intubation (see Chapter 2 ), but despite these advances, most patients who need assisted ventilation or positive pressure to improve oxygenation require intubation.^[]

Anticipated Clinical Course

Certain conditions indicate the need for intubation even in the absence of frank airway, ventilatory, or oxygenation failure. These conditions are myriad and are characterized by a reasonable likelihood of predictable deterioration that would require airway intervention either to preserve the airway and ventilation or as part of the overall management of the patient. Intubation may be indicated relatively early in the course of severe cyclic antidepressant overdose. Although the patient is awake, protecting the airway, and exchanging gas well, intubation is advisable to guard against the strong likelihood of clinical deterioration, which can occur relatively abruptly and includes coma, seizure, cardiac dysrhythmia or arrest, and possible aspiration of activated charcoal or gastric contents.

Significant multiple trauma, with or without head injury, may be an indication for intubation.^[] Many of these patients are ventilating normally through a patent airway, and oxygen levels frequently are normal or supernormal with supplemental oxygen. Despite this, anticipated deterioration, loss of the ability to protect the airway, the need for invasive and painful procedures, or the need for studies outside the emergency department (e.g., computed tomography, angiography) may mandate intubation.^[16] A patient with penetrating neck trauma may present with a patent airway and adequate gas exchange. Nevertheless, intubation is advisable with any evidence of vascular or direct airway injury because these patients tend to deteriorate and because increasing hemorrhage or swelling in the neck tends to both compromise the airway and confound later attempts at intubation.^[]

Although these indications for intubation may seem quite different and individualized, the common thread is the anticipated clinical course over time. In each circumstance, it can be anticipated that future events will compromise either the patient’s ability to maintain and protect the airway or the patient’s ability to oxygenate and ventilate. Knowledge of the natural history of the emergency condition is essential to determine whether intubation is necessary when airway compromise or gas exchange failure is not present on evaluation. A similar thought process is applied to any patient who will be leaving the emergency department for diagnostic studies (e.g., a computed tomography scan) or who may be transported to another facility. If it seems clinically likely that the patient may deteriorate, ‘prophylactic’ or ‘preemptive’ intubation is the prudent course.