Virtual Disaster Medicine

Training Center (VDMTC)

Module 12

The American Society of Anesthesiologists' Management

of the Difficult Airway Algorithm and Explanation-Analysis of the Algorithm

Problems with the ASA Algorithm and Likely Future Directions

The ASA Difficult Airway Management Algorithm has been before the anesthesia community, in one form or another, since 1991.  This algorithum has undergone revisions as our knowledge and experience with managing the airway has grown and as new devices and techniques have become available.  The strength of the ASA Difficult Airway Management Algorithum is twofold.  First, it is very thorough and complete with respect to the options available when an anesthesiologist encounters a difficult airway.  Second, it emphasizes the need for and importance of an organized approach to airway management.⁴⁰

On the other hand, the algorithm has several deficiencies that diminish its application in clinical practice.  First, although intended to apply to all patients of all ages, there are certain patient populations in which further considerations are necessary (e.g., pediatric and obstetric patients; see Chapters 33 and 34, respectively, non-fasted patients or patients with obstruction at or below the vocal cords).  Second, its clinical endpoint is successful intubation, but endotracheal intubation may not be necessary and successful ventilation may suffice.  Third, the algorithm is fairly complex, allowing a wide choice of techniques at each stage and its multiplicity of pathways may limit its clinical usefulness in guiding day to day practice.  It is not binary in nature, such as the algorithm used in advanced life support guidelines.²⁰  Fourth, somewhat vague terminology is used in its definitions of difficult tracheal intubation and difficult laryngoscopy.  Definitions of optimal-best attempts at conventional laryngoscopy, mask ventilation, and difficult laryngoscopy/intubation is important because it provides an end point at which practitioners may quit this approach (limit risk) and move on to something that has a better chance of nothing (gain benefit).  Fifth, the algorithm mentions ablation of spontaneous ventilation with muscle relaxants but does not discuss the great clinical management implications of muscle relaxants that have different durations of action.  Sixth, although the algorithm advises confirmation of endotracheal intubation, the usefulness of capnography for this purpose is limited during cardiac arrest, which is not an uncommon consequence of ‘cannot intubate-cannot ventilate’ (CICV) scenerio, whereas the esophageal detector device is not (see Chapter 30). Seventh, it doesn’t provide a definitive flow chart for extubation of the difficult airway, which incorporates the use of a device that can serve as a guide for expedited reintubation or ventilation, if necessary.  Finally, the role of regional anesthesia in patients with a difficult airway requires further clarification (see Chapter 42).

DEFINITION OF DIFFICULT ENDOTRACHEAL INTUBATION

At present, the ASA Difficult Airway Management Algorithm defines difficult endotracheal intubation as “when tracheal intubation requires multiple attempts in the presence of tracheal pathology,” and difficult laryngoscopy as “not being able to visualize any portion of the vocal cords after multiple attempts at conventional lavyngoscopy.”  Since these definitions do not state a specific number of attempts, they can be interpreted differently by practitioners.  Multiple may mean more than one, more or greater than 2, more or greater than 3, etc.  Although this imprecise terminology may be deliberate, it may be more appropriate to provide a definitive number of attempts or not include a number at all, and better define attempt (e.g., assuming best optimal attempt is utilized, and that an attempt is the physical placement and removal of the laryngoscope blade).

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