Women emerge from general anesthesia with propofol/alfentanil/nitrous oxide faster than men

Background: Recovery from general anesthesia is governed by pharmacodynamic and pharmacokinetic factors. Gender has not previously been recognized as a factor influencing the time to emergence from general anesthesia. Methods: This multicenter study was originally designed to measure the effe cts of the bispectral index on intraoperative anesthetic management and pat ient recovery. We compared the wake-up and recovery times of 274 adults aft er propofol/alfentanil/nitrous oxide anesthesia. Patients were randomly ass igned to have the titration of propofol performed with or without the use o f bispectral index monitoring. Specific guidelines were given for the titra tion of drugs. The aim in all cases was to provide a safe anesthetic with t he fastest possible recovery. Results: There was a significant reduction in propofol dose, time to eye op ening, and response to verbal command when the anesthetic was titrated usin g the bispectral index. Unexpectedly, gender proved to be a highly signific ant independent predictor for recovery time. Women woke significantly faste r than men: the time from end of anesthesia to eye opening was 7.05 versus 11.22 min, P < 0.05, and response to verbal command was 8.12 versus 11.67 m in, P < 0.05. These differences were significant at all four study sites an d in each treatment group. Men consistently had prolonged recovery times co mpared to women, P < 0.001, There was no difference in the dose of anesthet ic used between gender. Conclusions: Gender appears to be an important variable in recovery from ge neral anesthesia. These findings may explain the increased reported inciden ce of awareness in women (three times more frequent) and support the need t o include gender as a variable in pharmacokinetic and pharmacodynamic studi es of anesthetic drugs.