The airway approach algorithm: a decision tree for organizing preoperative airway information

Abstract

Anticipatory decision-making in airway management requires the integration of both history and physical examination findings. Though all airways can be managed along some branch of the American Society of Anesthesiologists' (ASA) Difficult Airway Algorithm, by predicting specific difficulties and integrating this information into an airway approach strategy, emergency branches of the ASA algorithm may be avoided. The Airway Approach Algorithm (AAA) consists of five clinical questions, with “yes” or “no” answers, to be addressed prior to the management of the airway. A positive answer to any question leads the clinician to the next, whereas a negative answer directs the operator to a root point of the ASA algorithm. The AAA is introduced with the anticipation that trainees in Anesthesiology, as well as others, will find it helpful in organizing preoperative information concerning the airway.

Introduction

In 1993, the American Society of Anesthesiologists' (ASA) Task Force on the Difficult Airway published an algorithm that is the foundation of airway management practice.1 These guidelines have been recently updated. 2 The ASA-Difficult Airway Algorithm (DAA) gives clinicians a rational decision tree to follow when faced with the anticipated difficult airway, the cannot intubate/can ventilate nonemergency, and the cannot intubate/cannot ventilate emergency. 2 Based upon the clinician's preoperative evaluation, the airway management of all patients undergoing general anesthesia with tracheal intubation follows a branch of the DAA commencing at one of the two root points: awake intubation (Figure 1, Box A) or intubation after anesthetic induction (Figure 1, Box B) Though stressing that the clinician must make this initial root distinction, the Task Force provided little guidance to this end, noting that routine preoperative evaluation “rating systems exhibit modest sensitivity and specificity.”1, 2

Identifying the truly difficult airway can be problematic. An airway may be considered difficult for mask ventilation, supralaryngeal ventilation, direct laryngoscopy (DL), DL and tracheal intubation, or intubation by other means (e.g., fiberoptic bronchoscope, retrograde wire, intubating laryngeal mask, etc.). The profound effect that the utilization of supralaryngeal airways (SLA) has had on routine, emergency, and rescue airway management has influenced the most significant change made in the 2003 revision—the removal of the LMA from the emergency pathway. The LMA is now considered within the algorithm to be a nonemergency mode of ventilation.* ^,2, 3

The 2003 revision of the guidelines also recognized that the proliferation of routine supralaryngeal ventilation has altered many practitioners' views on what constitutes the difficult airway.2, 4 This concept was first broached by Tekenaka et al.5 in 2000. In a letter, these authors proposed an algorithm for electively managing the patient who appears to have an airway that might be difficult but not impossible to intubate via direct laryngoscopy. They suggested that the induction of anesthesia could proceed as long as a laryngeal mask airway (LMA) was available for airway rescue should DL fail: this supralaryngeal airway offers the clinician a high success rate, even in patients with physical characteristics compatible with difficult laryngoscopy.2 This brief report by Tekenaka et al. did not define which patients would be candidates for such an approach. In identifying these patients, the ability to ventilate with a supralaryngeal device and minimal aspiration risk would need to be assured to the best of the clinician's judgment. An evaluation of these factors, as well as the likely ease or difficulty of DL, and the risk to the patient of a judgment error could be integrated into preanesthetic airway assessment in a manner, which draws on the concepts of Tekenaka et al. Such an assessment protocol could aid not only in choosing an appropriate root of the DAA, but also in anticipating the course along the algorithmic tree. Anticipating a pathway, which leads to an undesirable branch, could allow reconsideration of the entry root. This report describes a decision tree approach to patient evaluation. The “Airway Approach Algorithm” (AAA) is meant to be used by the clinician prior to the induction of anesthesia to organize information vital to airway evaluation, choose an appropriate DAA entry root and avoid the emergency branch of the DAA.