The Difficult Airway Algorithm of the American Society of Anesthesiologists

To the Editor:

The Difficult Airway Algorithm of the American Society of Anesthesiologists (ASA) was developed to guide clinicians in the management of the patient who is either predicted to have a difficult airway or whose airway cannot be adequately managed after induction of anesthesia ⁽¹⁾. Though the ASA’s task force did not attempt to enumerate the features which identify those patients who may prove difficult to manage, they did recognize that an airway evaluation should be performed. In their algorithmic approach, the task force also did not contemplate the possibility of using supralaryngeal airway devices in the routine anesthetic care of patients whose preoperative evaluation predicted difficulty with direct laryngoscopy. This concept was broached by Takenaka et al ⁽²⁾. These authors suggested that when a patient presents with inconclusive evidence of a difficulty airway, it is reasonable to proceed with the induction of anesthesia, with a plan to use a laryngeal mask airway should direct laryngoscopy fail. In their algorithm, these authors suggested that conclusively identified difficult airways should be managed with awake intubation.

While we agree with the premise that all patients anticipated to be a “difficult direct laryngoscopy” do not require awake intubation, the Tekenaka et al algorithm was incomplete in defining those situations where the clinician may proceed with the induction of general anesthesia and laryngoscopy, with a supralaryngeal airway acting as a contingency and/or “rescue” device.

In response to this, we have developed a preoperative decision tree, the goal of which is to aid the clinician in organizing pertinent information regarding the patient, so that a rational choice in airway management can be made (Fig. 1). Like the ASA Algorithm, the Airway Approach Algorithm (AAA) is not meant to help identify all difficult airways, but rather to manage all airways in a safe and rational fashion. However, unlike the ASA Algorithm, whose most significant contribution is in airway rescue, the AAA is meant to be a cognitive exercise prior to the induction of anesthesia. Once the AAA has been completed, the ASA algorithm is applied as appropriate.

Figure 1: The Airway Approach Algorithm.

The AAA consists of five questions. A positive answer to any question leads the clinician onto the next, whereas a negative answer suggests an airway management option. The algorithm makes no pretense as to be able to direct how a clinician should answer each question: for example, a particular Mallampati grade, thyromental distance or similar index does not trigger a difficult laryngoscopy “arm.” The answer to each question will depend on the individual practitioner’s clinical experience and review of the evidence based data.

Though seasoned clinicians who have casually reviewed the AAA concept have acknowledged that it agrees with their subjective assessments, this concept has been especially helpful for our trainees who are still trying to organize their perioperative assessment thoughts. We put forth the AAA concept as a tool for the novice (or more experienced clinician) to use in formulating airway management strategies. We are currently designing protocols to test the usefulness of this algorithm, and invite comments from readers.

William H. Rosenblatt, MD

Joy Whipple, MD