The ASA Difficult Airway Algorithm: New Thoughts and Considerations Chen, Chien-Yu June 8, 2001

Introduction and Recognition Of A Difficult Airway ASA difficult airway algorithm ( from Anesthesiology 1993, 1996) Pre-op airway evaluation: The more predictors used, the better the prediction

Recognized Unrecognized Awake intubation choices LMA Combitube TTJV Mask ventilation Intubation Choices Intubation Choices

Pre-op airway evaluation (1) No equipment,noninvasive, less than 1 min 1.Teeth 2. Inside of the month 3. Mandibular space 4. Neck

Pre-op airway evaluation (2) Usually it is the combination of findings that determines the index of suspicion of airway difficulty Pathological state ( cancer, infection, bleeding, disruption) Bread Obesity Large breast

Recognized difficult airway- awake limb of algorithm (1) Difficult airway (DA) Awake Intubation

Recognized difficult airway- awake limb of algorithm (2) Proper preparation is the most important determination of the success of an awake intubation Psychological support Use of drying agent Titrated sedation Vasoconstriction Nerve block

Recognized difficult airway- awake limb of algorithm (3) Very occasionally awake intubation may fail due to either lack of p’t cooperation, equipment and operator limitation Fail of awake intubate: Re-prepare Cancel the op GA Regional anesthesia Surgical airway

Recognized difficult airway- awake limb of algorithm (4) Surgical airway first choice Laryngeal/ tracheal disruption Upper airway abscess Mandibular-maxillary fracture

Recognized difficult airway- awake limb of algorithm (5) Use of regional anesthesia in a patient with a known difficult airway requires a high degree of judgment

Unrecognized difficult airway (1) Mask ventilation  nonemergency pathway 考慮是否使用conventional laryngoscopy  缺點: edema, bleeding  惡化mask ventilation and intubation  CVCI  Plan B

Unrecognized difficult airway (2) Definition of optimal intubation attempt reasonably experienced endoscopist: 2-3 yrs no significant muscle tone optimal sniff position optimal external laryngeal pressure change length of blade*1 change type of blade*1

Unrecognized difficult airway (3) Macintosh blade-- small narrow month, palate, oropharynx Miller blade-- small mandibular space, large incisors, long floppy epiglottis

Unrecognized difficult airway (4) DA 又可定義 laryngoscope use > 3 attempts and/or > 10 min Laryngoscope fail 後的choices  fiberoptic intubation, LMA, airway intubator  mask ventilation  awaken or surgical airway

CVCI (1) 2 persons effort: Better mask seal Jaw thrust Better tidal volume Large oral pharyngeal, nasopharyngeal airways

CVCI (2) The decision to abandon mask ventilation should be made after the anesthesiologist has made an optimal/best attempt at mask ventilation

CVCI (3) 8.5 min fully preoxygenated, p‘t 也會hypoxemic, dead 給1mg/kg SCC, 50% recovery P’t will die before SCC wear off awaken option  0.5-0.7 mg/kg

CVCI (4) LMA or Combitube-- conduit for fiberscope work as ventilatory mechanism few complications inserted blindly, quickly, low level of skill can’t solve glottic, subglottic problems TTJV-- barotrauma