Laryngoscopy in conscious patients with remifentanil: how useful is an "awake look"?

To determine the sensitivity and specificity of direct laryngoscopy in the conscious patient as a diagnostic test for difficult direct laryngoscopy in the unconscious patient.

Prospective case series.

Various operating rooms in a Canadian tertiary-care hospital.

81 ASA physical status 1, 2, and 3 subjects undergoing elective surgery.

A bolus of midazolam was given and a continuous infusion of remifentanil was started and adjusted as needed. Direct laryngoscopy was performed in the conscious subject. No topical anesthesia was applied to the upper airway.

The modified Cormack-Lehane grade was recorded with each subject conscious and unconscious. Other data collected before the intervention included age, gender, height, weight, body mass index, Mallampati class, thyromental distance, mouth opening, previous history of failed or difficult intubation, history of hypertension or obstructive sleep apnea, and routine use of beta blockers. The time of intravenous placement, total dose and duration of remifentanil infusion, and time of endotracheal tube placement were recorded. The lowest oxygen saturation, lowest and highest systolic blood pressure and heart rate, and presence or absence of gagging, coughing, or chest wall rigidity were also noted. Subjects were also asked to complete a questionnaire in the recovery room regarding recall and the degree of discomfort experienced.

43 of 81 subjects were graded 1 or 2a when the laryngoscopy was done in the conscious subject. Six of the 38 subjects who were graded as a difficult laryngoscopy (grade 2b or higher) when they were conscious also remained a difficult laryngoscopy when unconscious and paralyzed. Sensitivity and specificity of direct laryngoscopy in the conscious subject as a diagnostic test for difficult direct laryngoscopy in the unconscious subject were 100% [95% confidence interval (CI) 0.52 to 1] and 57% (95% CI 0.47 to 0.70), respectively.

Using remifentanil as the sole analgesic allows evaluation of the larynx with direct laryngoscopy in a conscious patient. A poor Cormack-Lehane grade in a conscious patient may or may not improve with general anesthesia.