The Decision to Intubate
Ron M. Walls
Timely, effective airway management in an emergency can mean the difference between life and death, or between ability and disability. As such, airway management is the single most important skill of the emergency physician, and emergency airway management is one of the defining domains of the specialty of emergency medicine. Anesthesia providers, hospitalists, and intensivists often are called upon as the primary responders to airway emergencies arising in hospital inpatient units. Paramedics and critical care transport personnel are responsible for the out-of-hospital airway. Regardless of specialty or locus of care, these practitioners must maintain the cognitive base and technical skill set required for swift, decisive airway management, which is often required without warning and in suboptimal circumstances.
The emergence of new technology, principally the various methods of video laryngoscopy, is changing the fundamental approach to airway decision-making, particularly with respect to difficult intubation. Nevertheless, emergency airway management, whether in the emergency department (ED) or elsewhere in the hospital or prehospital setting, still comprises a series of complex actions:
Rapidly assess the patient’s need for intubation and the urgency of the situation.
Determine the best method of airway management.
Decide whether pharmacologic agents are indicated, which to use, in what order, and in what doses.
Construct a plan in the event that the primary method is unsuccessful; recognize when the planned airway intervention has failed, and quickly and effectively execute the alternative (rescue) technique.
Physicians responsible for emergency airway management must be proficient with the techniques and medications used for rapid sequence intubation, the preferred method for most emergency intubations. The entire repertoire of airway skills must be mastered, including bag-mask ventilation, conventional and video laryngoscopy, flexible endoscopy, the use of extraglottic airway devices, adjunctive techniques such as use of an endotracheal tube introducer (ETI, EI; also known as the gum elastic bougie), and surgical airway techniques (e.g., cricothyrotomy).
This chapter focuses on the decision to intubate. Subsequent chapters describe airway management decision-making, methods of ensuring oxygenation, techniques and devices for airway management, the pharmacology of airway management, and considerations for certain special clinical circumstances, including the prehospital environment and care of pediatric patients.
INDICATIONS FOR INTUBATION
The decision to intubate is based on three fundamental clinical assessments:
1. Is there a failure of airway maintenance or protection?
2 Is there a failure of ventilation or oxygenation?
3. What is the anticipated clinical course?
The results of these three evaluations will lead to a correct decision to intubate or not to intubate in virtually all conceivable cases.
A. Is there a failure of airway maintenance or protection?
A patent airway is essential for adequate oxygenation and ventilation, and protection of the airway against aspiration of gastric contents is vital. The conscious, alert patient uses the musculature of the upper airway and various protective reflexes to maintain a patent airway and to protect against the aspiration of foreign substances, gastric contents, or secretions. The ability of the patient to phonate with a clear, unobstructed voice is strong evidence of both airway patency and protection. In the severely ill or injured patient, such airway maintenance and protection mechanisms are often attenuated or lost. If the spontaneously breathing patient is
not able to maintain a patent airway, an artificial airway may be established by the insertion of an oropharyngeal airway or a nasopharyngeal airway. Although such airway devices may restore a patent airway, they do not provide any protection against aspiration. As a general rule, any patient who requires the establishment of a patent airway also requires protection of that airway, and the use of an oropharyngeal or nasopharyngeal airway should be considered a temporizing measure, pending establishment of a definitive airway: placement of an appropriate (cuffed for adults and uncuffed for small children) endotracheal tube in the trachea.
not able to maintain a patent airway, an artificial airway may be established by the insertion of an oropharyngeal airway or a nasopharyngeal airway. Although such airway devices may restore a patent airway, they do not provide any protection against aspiration. As a general rule, any patient who requires the establishment of a patent airway also requires protection of that airway, and the use of an oropharyngeal or nasopharyngeal airway should be considered a temporizing measure, pending establishment of a definitive airway: placement of an appropriate (cuffed for adults and uncuffed for small children) endotracheal tube in the trachea.
A patient who is seemingly able to maintain a patent airway and adequate gas exchange cannot be assumed to be able to protect the airway against the aspiration of gastric contents, which carries a significantly increased risk of morbidity and mortality. It has been widely taught that the gag reflex is a reliable method of evaluating airway protective reflexes. In fact, this concept has never been subjected to adequate scientific scrutiny, and the absence of a gag reflex is neither sensitive nor specific as an indicator of loss of airway protective reflexes. The presence of a gag reflex has similarly not been demonstrated to ensure the presence of airway protection. In addition, testing the gag reflex in a supine, obtunded patient may result in vomiting and possible aspiration. Accordingly, the gag reflex is of no clinical value when assessing the need for intubation and should not be used for this purpose.
The assessment of spontaneous or volitional swallowing is probably a better assessment of the patient’s ability to protect the airway than is the presence or absence of a gag reflex. Swallowing is a complex reflex that requires the patient to sense the presence of material in the posterior oropharynx and then to execute a series of intricate and coordinated muscular actions to direct the secretions down past a closed airway into the esophagus. The finding of pooled secretions in the patient’s posterior oropharynx indicates a potential failure of these protective mechanisms, hence a failure of airway protection. In the absence of an immediately reversible condition, such as opioid overdose or reversible cardiac dysrhythmia, prompt intubation is indicated for any patient who is unable to maintain and protect the airway. A common clinical error is to assume that spontaneous breathing is proof that the ability to protect the airway is preserved. Although spontaneous ventilation may be adequate, the patient may be sufficiently obtunded to be at serious risk of aspiration.
B. Is there a failure of ventilation or oxygenation?
Stated simply, “gas exchange” is adequate to sustain vital organ function. If the patient is unable to ventilate adequately, or if adequate oxygenation cannot be achieved despite the use of supplemental oxygen, then intubation is indicated. In such cases, the intubation is performed to facilitate ventilation and oxygenation rather than to establish or protect the airway. An example is the patient with status asthmaticus, for whom bronchospasm and fatigue lead to ventilatory failure and hypoxemia, heralding respiratory arrest and death. Airway intervention is indicated when it is determined that the patient will not respond sufficiently to treatment to reverse the cascading events leading to respiratory arrest. Similarly, although the patient with severe acute respiratory distress syndrome may be maintaining and protecting the airway, he or she may have progressive oxygenation failure and supervening fatigue that can be managed only with tracheal intubation and positive-pressure ventilation. Unless ventilatory or oxygenation failure is resulting from a rapidly reversible cause, such as opioid overdose, intubation is required.
C. What is the anticipated clinical course?
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