The Airway Approach Algorithm

The Airway Approach Algorithm

William H. Rosenblatt

It goes without saying, though it is often said, that the most important job of the anesthesia provider is airway management. The occurrence of rescue surgical airway in the elective OR suite is extraordinarily low. Kheterpal et al. recently demonstrated that the incidence of cannot-intubate, cannot-ventilate with face mask or SGA is approximately 1 in 176,000 patients. Yet, in the emergency department (ED) the rescue surgical airway may occur in 6 in 1,000 patients requiring tracheal intubation. Are we, as anesthesia providers, so much better at airway management than our ED colleagues? No, of course not. What accounts for superior success rates in our arena is the luxury of (1) managing patients who can be thoroughly evaluated and optimized, (2) asking for the right instrumentation, and (3) having stable patients on whom we can choose awake airway management. Of course, there will be situations when those luxuries are limited, yet no case in the ED can be “canceled.” On the other hand, our thoughtful approach to so many airways gives us experience that makes anesthesiology a true airway management specialty.

But differences in the skill and capabilities of anesthesia providers will and does vary. Individual variances in clinical experience, daily practice, a yearning to master new techniques, and even gaming proficiency will contribute to not only one’s deftness in managing the difficult patient, but also in the way we choose to manage that patient. Making decisions based not only on available information, but also on the order in which it is considered, is the foundation of good airway management.

The difficult airway algorithm of the American Society of Anesthesiologists (ASAs) has become a gold standard for how we manage airways that prove difficult. But even a cursory examination of the algorithm reveals two fundamental elements that contradict its very name—every patient’s airway is managed in an arm of the algorithm and there are only two entry points into its decision tree: (a) awake intubation and (b) airway management after the induction of anesthesia (Fig. 1.1). The latter, Box B, is the root node for the vast majority of general anesthesia cases. In the case of Box A, awake intubation is often chosen on a presumption of difficulty; therefore, whether the airway is truly difficult may never be known. It is truly an “airway algorithm” as opposed to a “difficult airway algorithm.”

A fundamental condition for applying the ASA’s difficult airway algorithm is that the anesthesia provider makes a critical decision during the evaluation period—which root node is to be entered? The ASA’s Difficult Airway Taskforce asks the reader to ponder basic elements beyond the physical examination and airway history. Each decision is tempered by the experience of the operator, the availability of resources, and the current state of the patient. Once considered, the algorithm is entered at one of the two root nodes. Because the goal of evaluation and the subsequent election of the correct entry point is to keep the patient in a safe state, the luxury of preanesthetic induction choice becomes manifest—the operator can consider all elements and choose the root which will best avoid a failed airway scenario.

This decision tree approach is illustrated in Figure 1.2, the Airway Approach Algorithm (AAA). The provider starts by asking if airway management is necessary (Fig. 1.2, question 1). Taking control of a patient’s airway is a considerable action. The patient’s most elemental survival mechanisms are obtunded and control of oxygenation and ventilation are assumed by the anesthesia provider. Should airway control not be necessary, the provider should consider the feasibility of regional or infiltrative anesthesia. This does not excuse the formulation of an airway plan. In the analysis of airway-related claims in the ASA’s closed claims database, Peterson states that “use of a local anesthetic or regional nerve block does not obviate the need for a strategy for intubation of the difficult airway.” Failure of a regional block, or loss of adequate ventilation and oxygenation during the same, may require airway support and possibly general anesthesia.

Because definitive airway management is most often considered tracheal intubation, we next ask if for any given patient, this will be difficult (Fig. 1.2, question 2). Three factors will affect the anesthesia provider’s answer to this question: patient evaluation, available instrumentation and the operator’s experience with that instrument, and the operator’s risk tolerance. Of the three, the latter is the most dynamic. Yentis points out that unless a test (or index) applied to judge the ease of laryngoscopy and intubation is 100% sensitive, there will always be a number of false-negative findings (false-positive findings are less likely to sway a decision in a way that causes harm, though they may consume resources of equipment, time, and energy). Each time the operator makes a decision based on an imperfect test, an element of risk is accepted. If the operator is risk adverse
that day (e.g., possibly yesterday he/she had a bad outcome during airway management), they are more likely to err on the side of caution. If they are risk tolerant, they are more likely to accept a degree of jeopardy. For this reason, the AAA advises that the answer to the question “will laryngoscopy and intubation be at all difficult” be scored “yes” whenever a minor degree of uncertainty exists. In other words, the most sensitive test should be employed in order to capture all potentially difficult laryngoscopies and intubations. This approach retains the patient within the decision-making process, though it does not imply that the airway will be treated as difficult. The question should be answered “no” only when, in the operator’s opinion, the most sensitive test is negative. In that case, when in the operator’s mind laryngoscopy and tracheal intubation are certain, the ASA’s difficult airway algorithm is entered at the root node B—intubation attempts after the induction of anesthesia. This is akin to the choice of RSI—No consideration is made for the ease of mask ventilation. If, on the induction of anesthesia, the patient proves difficult to intubate (by the operator’s choice of instrumentation), the ASA’s difficult airway algorithm, or those of other organizations, suggests emergency pathways.

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Mar 5, 2021 | Posted by in GENERAL | Comments Off on The Airway Approach Algorithm
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