Bispectral index monitoring does not improve early recovery of geriatric outpatients undergoing brief surgical procedures

Abstract

To assess if titration of sevoflurane using the bispectral index (BIS) monitor improves the early and intermediate recovery in geriatric outpatients undergoing brief urologic procedures under general anesthesia without muscle relaxants. After a standardized induction with propofol and fentanyl, a laryngeal mask airway was inserted and sevoflurane was administered in combination with 60% nitrous oxide in oxygen for maintenance of anesthesia in spontaneously breathing outpatients. In the Control group (n = 25), sevoflurane and fentanyl were titrated according to standard clinical practice. In the BIS-directed group (n = 25), sevoflurane was titrated to maintain a BIS value between 50 and 60, and supplemental fentanyl, 25 mug iv boluses were administered to treat tachypnea. The intraoperative anesthetic and analgesic requirements, as well as the times to eye opening, removal of the laryngeal mask airway device, response to simple commands, orientation to person and place, and postanesthesia care unit discharge eligibility (fast-track score of 14) were assessed at specific time intervals. The minimum alveolar concentration-hour of sevoflurane (0.25 +/- 0.15 and 0.31 +/- 0.2) and end-tidal concentrations of sevoflurane at the end of surgery (0.3 +/- 0.3 and 0.4 +/- 0.20%) did not differ significantly between the Control and BIS-directed groups, respectively. Although the percentage of patients requiring supplemental boluses of fentanyl was reduced in the BIS-directed group (16 vs 48%, P <0.05), the intraoperative BIS values and recovery times were similar in the two groups. In this non-paralyzed elderly outpatient surgery population, the use of BIS monitoring for titrating the maintenance anesthetic (sevoflurane) failed to improve the early recovery process.