Influence of gender on propofol consumption and recovery times

Introduction. We investigated gender differences of drug consumption and recovery times for propofol-remifentanil anaesthesia. Methods. Adult patients scheduled for minor orthopaedic surgery were randomised to receive a propofol-remifentanil anaesthesia controlled either by EEG monitoring (Narcotrend or BIS) or solely by clinical parameters. Anaesthesia was induced with remifentanil 0.4 mu g/kg/min and a propofol target-controlled infusion (TCI) at 3.5 mu g/ ml. After intubation remifentanil was reduced to 0.2 mu g/kg/min whereas propofol TCI was adjusted according to clinical parameters or to the following EEG target values: during maintenance to "D-0" (Narcotrend) or "50" (135), 15 min before the end of surgery to "C-1"(Narcotrend) or "60" (BIS). Recovery times were recorded and average normalised propofol consumption was calculated from induction and maintenance doses. Results. A total of 60 male and 60 female patients completed the study. Gender differences were observed for recovery times (with standard practice) and for propofol consumption (with BIS monitoring). In the standard protocol group, propofol consumption was nearly identical for male and female patients whereas recovery times were significantly longer in the male group. In both EEG-guided groups propofol consumption was less for male patients while recovery times were slightly longer. In the group of female patients higher propofol TCI concentrations had to be used to reach the same BIS or Narcotrend values. Conclusion. With propofol-remifentanil anaesthesia, gender has impact on recovery times and propofol consumption. If the same amounts of propofol are applied, males awake later, with BIS or Narcotrend monitoring males receive less propofol for comparable EEG effects.