Effect of remifentanil on cardiovascular and bispectral index responses following the induction of anesthesia with midazolam and subsequent tracheal intubation

Abstract

Purpose: We examined the hypothesis that remifentanil decreases the bispectral index (BIS) as well as blunts cardiovascular responses to tracheal intubation during anesthesia with midazolam.

Methods: Sixty patients were randomly allocated to three groups according to the dose of remifentanil-0.1 (S), 0.2 (M), or 0.5 (L) microg kg(-1) min(-1), respectively. Infusion of remifentanil was started 5 min before the induction of general anesthesia with midazolam 0.2 mg/kg in all groups. Following the administration of vecuronium 0.1 mg/kg, the trachea was intubated 5 min after induction, and the infusion rate of remifentanil was then reduced to 0.05 microg kg(-1) min(-1) in all groups. Mean arterial blood pressure (MAP), heart rate (HR), BIS, and 95% spectral edge frequency (SEF95) were measured until 10 min after tracheal intubation.

Results: Infusion of remifentanil alone before the induction of anesthesia did not affect the hemodynamic or electroencephalographic parameters. MAP was significantly decreased after induction in all groups of patients (P < 0.01), with no differences among the three groups, while it was significantly increased after tracheal intubation in the patients of groups S and M, but not in those of group L. The HR did not change after induction in any of the groups, but it was also significantly increased after tracheal intubation of group S and M patients, although not in those of group L. The BIS decreased after induction, and both the BIS and SEF95 were significantly lower in group L patients than in those of group S (P < 0.01). All patients were unconscious after induction, and none complained of intraoperative awareness.

Conclusion: In our patient cohort, remifentanil 0.5 microg kg(-1) min(-1) effectively decreased the BIS after the induction of general anesthesia with midazolam 0.2 mg/kg and suppressed the increase of MAP and HR in response to subsequent laryngoscopy and tracheal intubation.