Difficult and Failed Airway Management in EMS

THE PREHOSPITAL CHALLENGE

As discussed in Chapter 29, the prehospital environment presents an array of unique challenges to the prehospital provider including, but not limited to, noise, bright sunlight or darkness, temperature extremes, patient access issues, and challenges in patient positioning. Taken in sum, it is clear that all airway management in the prehospital setting should be treated as difficult, although careful evaluation for specific features predicting difficulty is still warranted to allow any modifiable factors to be addressed and to make a comprehensive informed decision about whether, and how, to proceed. Experience would suggest that errors in prehospital medication-facilitated airway management (MFAM) are more often errors in decision making than errors in performance of purely technical skills, often related to a failure to anticipate difficulty.

PREDICTION OF THE DIFFICULT AIRWAY IN THE PREHOSPITAL SETTING

The anatomic and physiologic factors governing the prediction of difficult intubation, difficult bag-mask ventilation (BMV), difficult extraglottic airway placement and ventilation, and difficult performance of a cricothyroidotomy are all discussed at length in Chapter 2, and for the most part apply equally well in the prehospital setting. In emergency medical services (EMS), however, we modify the LEMON mnemonic to become LEMONS with the “S” standing for Situation. Situational factors to consider include immediate hazards, personnel and equipment resources and limitations, environmental considerations, limitations in patient access and positioning, planned mode of transportation, and transport time. For example, an edentulous thin patient with no anatomic predictors of difficulty may become very difficult to manage when trapped in a vehicle at night with an ambient temperature of 20°F and snow. Physiologic factors contributing to difficulty are also paramount in the prehospital setting just as they are in the hospital. The patient’s oxygen saturation, after attempts at optimal preoxygenation, will be a major determinant of the time available for laryngoscopy before it becomes necessary to abort. When time is limited, many borderline laryngoscopy and intubation cases become impossible. In other words, preoxygenation creates reserve and reserve creates time, which in turn results in greater intubation success. Careful evaluation for anatomic, physiologic, and situational factors that may cause airway difficulty allow the provider to make informed decisions and establish an optimal primary backup and rescue airway plan.

THE PREHOSPITAL CONUNDRUM

Although basic airway measures can never wait, prehospital providers have the unique option to defer advanced airway management until arrival at an emergency department (ED). Therefore, predictive factors must be placed into a more complicated decision algorithm that not only includes questions such as “Does this patient need advanced airway management?” but also “Does this patient need advanced airway management right now?” and “Is this patient better served by airway management now or delaying until arrival at the hospital or arrival of additional providers such as a critical care transport team?” These questions must be asked before rushing a patient off the scene into a moving ambulance to avoid critical airway compromise during transport. In addition, some patients, such as those with inhalation injury or anaphylaxis, may have better outcomes if managed aggressively early, when they have more reserve and/or before their disease process progresses. Given these factors, the decision to embark on invasive airway management is complex.

When Is it Better to Wait?

Although this question should be asked with every emergency airway encounter, it is particularly important in the prehospital setting. Consider, for example, the following two cases, each with an anticipated 10-minute transport time to an appropriate receiving facility:

• A 40-year-old, 80-kg man with sudden collapse, new left hemiparesis, Glasgow Coma Scale of 6, marked hypertension, no swallowing reflex, normal respiratory pattern with O₂ saturations of 99%, nasal end-tidal CO₂ of 40, and severe ankylosing spondylitis.

• A 40-year-old, 80-kg man extricated from a house fire, with stridor, O₂ saturations of 70% despite mask ventilation, and evidence of upper airway burns.

Both patients have clear indications for securing the airway, although the decision process for the prehospital airway manager, particularly with respect to urgency, should be quite different. In the first case, if the patient is not deteriorating further, assessment of risks and potential benefits suggest it would be best to defer intubation to the ED, where a more formal and controlled rapid sequence intubation (RSI), augmented by difficult and failed airway tools, can be performed. In addition, alternate management options (such as awake techniques) for this predicted difficult airway are available and easier to perform in a hospital setting. In this case, the difficulty is related to a chronic condition, one that is unlikely to become more difficult if intubation is delayed until hospital arrival. The patient’s oxygenation and ventilation status is adequate, and although the patient is clearly at risk for aspiration, this is a theoretical risk or it may have already occurred. Training must emphasize that having the ability to perform a procedure, especially to prevent a complication that may or may not occur, does not always equate with the need to perform the procedure. The provider and system medical directors and administrators must be wary of the technical imperative—that operators generally will perform an authorized procedure more often than it is required or indicated. In fact, there is growing evidence that in certain situations, prehospital intubation may not improve outcomes and may even lead to worse outcomes (see Evidence section, Chapter 28).

In the second case, the provider is forced to actively manage the airway despite predicted difficulty with laryngoscopy. Even a brief delay, such as a 10-minute transport, allows time for further deterioration and hypoxemic damage, increasing the threat to the patient and making intubation progressively more difficult. If the provider is authorized to perform MFAM, the decision to intubate here is clear on the basis of “Forced to Act” (see Chapter 2). The non-MFAM ALS provider may be forced to perform a cricothyroidotomy. Thus, both the nature and the “stability” of the difficult airway become key factors in the “intubate-vs.-transport” decision. This has been previously identified as “context sensitive” airway management.

APPLYING THE EMS DIFFICULT AIRWAY ALGORITHM FOR MFAM PRACTITIONERS

The EMS difficult airway algorithm is modeled after the ED difficult airway algorithm and incorporates both predicted difficult airways and experienced difficult airway situations encountered in the prehospital environment, with modification as necessary to consider transport times, local protocols, preference, and medical direction (Fig. 30-1). The first step is to call for help when available from a second paramedic unit, a supervisor, or a critical care unit. Critical Care Transport providers managing patients at outlying hospitals should not overlook any providers that might be available in the facility.