Discussion
delirium, agitation
In this randomized controlled study, we observed the effects of a bolus of subanesthetic s-ketamine administered during elective laparoscopic gynecological surgery on emergence time in the female patients. We did not find a difference in the time duration from cessation of anesthetics to eye opening between the s-ketamine and saline groups. The agitation level, cognitive function and incidences of delirium, in the s-ketamine group were similar to those in the saline group. However, the administration of subanesthetic s-ketamine induced active EEG spectra with decreased power of slow wave, delta, and alpha bandwidths, and increased power of beta-gamma waves during sevoflurane anesthesia. The alpha peak frequency significantly increased.A synergistic interaction tends to occur when two or more drugs produce similar effects by different mechanisms [We did not find these differences in high-frequency and Ai values between the two groups during recovery period because of the fast metabolic rate of s-ketamine [However, these increases in indices of depth of anesthesia do not indicate the lightened hypnosis [The administration of ketamine (≤ 1 mg/kg i.v.) during general anesthesia has beneficial effects on cognition in elderly patients undergoing major surgery [Our study has some limitations. First, only young and middle-aged female patients were recruited, which may have avoided the bias of gender and age on anesthesia emergence [