Background: The bispectral index (BIS), a parameter derived from the electroencephalograph (EEG), has been shown to correlate with increasing sedation and loss of consciousness. This study determined whether addition of BIS monitoring to standard anesthetic practice results in improvements in the conduct of anesthesia or in patient outcomes.

Methods: Three hundred two patients receiving a propofol-alfentanil-nitrous oxide anesthetic were studied at four institutions. Thirty-four patients were initially enrolled to determine preexisting anesthetic practice and patient outcomes at each institution. Subsequent patients were randomized to either standard clinical practice (SP group), or standard practice plus BIS monitoring (BIS group). In all patients, the anesthesiologist attempted to provide a stable anesthetic with the fastest possible recovery. BIS was recorded for all patients, but viewed only in the BIS group. In the BIS group, propofol infusions were adjusted to achieve a target BIS between 45-60, increasing to 60-75 during the final 15 min of the case. In the SP group, propofol dose adjustments were made based only on standard clinical signs. Drug use, intraoperative responses, and patient recovery parameters were recorded.

Results: Demographics were similar between groups. Compared with the SP group, patients in the BIS group required lower normalized propofol infusion rates (134 vs. 116 microg x kg[-1] x min[-1]; P < 0.001), were extubated sooner (11.22 vs. 7.25 min; P < 0.003), had a higher percentage of patients oriented on arrival to PACU (43% vs. 23%; P < 0.02), had better postanesthesia care unit (PACU) nursing assessments (P < 0.001), and became eligible for discharge sooner (37.77 vs. 31.70 min; P <0.04). There was no significant difference in the incidence of intraoperative responses between the groups.

Conclusions: Titrating propofol with BIS monitoring during balanced anesthesia decreased propofol use and significantly improved recovery. Intraoperative course was not changed. These findings indicate that the use of BIS may be valuable in guiding the administration of propofol intraoperatively.