Airway Evaluation and Management - The Difficult Airway and Emergency Airway Techniques
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Difficult Airway. The 2013 revision of the American Society of Anesthesiologists (ASA) algorithm for managing difficult airways is shown in Figure 14.5. Familiarity with this algorithm is crucial for the anesthesiologist. Since its adoption in 1993, the number of death or brain death claims associated with airway-related events during induction of anesthesia has decreased significantly.
- The difficult airway can be divided into the recognized difficult airway and the unrecognized difficult airway; the latter presents the greater challenge for the anesthesiologist.
- The ASA defines a difficult airway as failure to intubate with conventional laryngoscopy after three attempts and/or failure to intubate with conventional laryngoscopy for more than 10 minutes. Others have suggested that a more appropriate definition of a difficult airway would be that of failure to intubate with conventional laryngoscopy after an optimal/best attempt. This optimal/best attempt is defined as an attempt with a reasonably experienced laryngoscopist, no significant resistive muscle tone, use of optimal sniffing position, use of external laryngeal manipulation, change of laryngoscope blade type a single time, and change of laryngoscope blade length a single time.
- The use of regional anesthesia as a way to avoid the known or anticipated difficult airway deserves special mention. Although the difficult airway algorithm advocates considering regional anesthesia, it must be kept in mind that the regional block can fail, or the patient may require rapid conversion to a general anesthetic for other reasons. Regional anesthesia generally should not be elected for a patient with a known difficult airway if the surgery cannot be terminated rapidly (in case of failed or inadequate block) or access to the patient's airway is compromised.
- The supraglottic airway device or LMA is a prominent airway option throughout the 2013 ASA difficult airway algorithm:
- An airway in patients who can be mask ventilated after general anesthesia is induced but cannot be intubated. It is also an alternative if awake intubation has failed (but only when general anesthesia and mask ventilation are not considered problematic).
- A conduit for intubation in patients who can be mask ventilated but cannot be intubated with conventional laryngoscopy.
- An airway in patients who cannot be intubated and cannot be ventilated. The Combitube and transtracheal jet ventilation are other options.
- A conduit for intubation in patients who cannot be intubated and cannot be ventilated (when a supraglottic airway is insufficient and intubation per se is needed).