• Akihiko Nonaka, Kenzo Makino, Satomi Suzuki, Kodai Ikemoto, Atsushi Furuya, Fumiaki Tamaki, and Nobumasa Asano.
• Department of Anesthesia, Yamanashi Prefectural Central Hospital, Kofu 400-8506.
• Masui. 2012 Apr 1;61(4):364-7.

BackgroundKetamine is associated with an increase in the bispectral index (BIS) values that can lead to an overdose of hypnotic agents. We investigated the effect of ketamine on BIS values during general anesthesia with a target-controlled infusion (TCI) of propofol and infusion of remifentanil.MethodsForty-five ASA I or II patients undergoing gynecological surgery were included in this study. After 5 min of steady-state anesthesia (BIS at 35-45) without surgical stimulation, patients received either a bolus administration of ketamine 0.2 mg x kg(-1) (LK group) or ketamine 0.5 mg x kg(-1) (HK group). Patients in the control group received no intervention. BIS values were recorded every minute until 15 min after ketamine administration.ResultsAfter ketamine administration, BIS value in HK group increased significantly compared with that at baseline. There were no significant changes for BIS values in LK group and control group over time. BIS values in HK group were significantly higher than those in the LK group and control group after ketamine injection. BIS values were not statistically different between LK group and control group.ConclusionsUnder stable propofol and remifentanil anesthesia, a small dose of ketamine did not increase the BIS value over the next 15 min.

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