Patient sex is an independent factor influencing the response to anaesthesia and recovery after surgery. Women emerged faster from general anaesthesia but their overall quality of recovery was poorer. Female sex hormones, particularly progesterone, might be involved, with premenopausal women having faster recovery time but poor overall recovery.

Physiological and pharmacological differences exist between men and women. Women wake faster than men following general anaesthesia. Women also differ from men in their postoperative recovery as reflected by differences in postoperative pain, nausea and vomiting and overall quality of recovery. These gender differences seem to be more pronounced in premenopausal women, suggesting hormonal mechanisms are a major contributing factor.

Previous studies suggest that women recover faster from general anesthesia than men, but it is unclear whether this is a result of a gender effect or differences in the pattern of drug administration or type of surgery. We performed a subset analysis comparing recovery characteristics from general anesthesia combined with neuromuscular blocking drugs of female and male patients, at risk of awareness, enrolled in a large trial testing the effectiveness of bispectral index (BIS) monitoring. We used multivariate statistical methods to adjust for differences in baseline characteristics, duration and extent of surgery, and anesthetic drug administration in 1079 patients (584 male, 495 female). Female patients had higher BIS values than male patients despite similar amounts of anesthetic drug administration (time-averaged mean [sd] BIS: male 44.6 [7.1] versus female 46.4 [6.6]; P = 0.005). Time to eye opening after anesthesia and time to eligibility to discharge from the postanesthesia care unit were less in women than men (male 13.9 [13.2] min versus female 10.6 [11.6] min; P < 0.001; male 133 [209] min versus female 78 [106] min; P < 0.001, respectively). These differences persisted after multivariate adjustment (both P < or = 0.001). Gender has an independent effect on recovery times in patients undergoing general anesthesia combined with neuromuscular blocking drugs, with women recovering faster than men. Higher BIS values during maintenance of anesthesia in women, despite similar amounts of anesthetic drug administration, suggests that women are less sensitive to the hypnotic effect of anesthetic drugs than men and may help explain faster recovery times in women.