Systolic blood pressure, not BIS, is associated with movement during laryngoscopy and intubation

To compare bispectral index (BIS) values to hemodynamic variations, in order to evaluate adequacy of anesthesia during orotracheal intubation with muscle relaxants.

Forty-one patients ASA I-II, scheduled for elective peripheral surgery under general anesthesia with tracheal intubation were enrolled in the study. Fentanyl/thiopental followed by vecuronium were used for induction. Onset of relaxation was monitored at the orbicularis occuli (OO) muscle using train-of-four stimulation. Intubation was performed when no response at the OO was detected visually. Intubating conditions were noted. The "isolated forearm" technique was used to detect movement during laryngoscopy/intubation. BIS values, pulse rate (PR), and systolic pressure were recorded before induction, during laryngoscopy/intubation and 60 sec after intubation.

Although intubating conditions were clinically adequate for all patients, ten out of 41 had movement of the isolated arm during laryngoscopy/intubation. BIS values were not significantly different for these patients: 67 (55-83) compared to those who had no movement: 60 (35-80), P = 0.6. During laryngoscopy, PR increased for all patients while systolic pressure increased significantly only in patients who moved: 125 (100-136) mmHg vs those who did not: 108 (67-140), P < 0.05.

Systolic pressure elevations were associated with inadequate anesthesia as evaluated by the "isolated forearm" technique, during laryngoscopy/intubation. BIS values were not different between groups, suggesting that systolic blood pressure may be a better predictor of inadequate anesthesia under the circumstances described.