• Takaaki Chino, Osamu Nagata, Masami Naitou, Haruyo Nagao, Minoru Nomura, and Makoto Ozaki.
• Department of Anesthesiology, Tokyo Women's Medical University, Tokyo.
• Masui. 2005 Apr 1;54(4):387-92.

BackgroundThere are some reports on the incidence of awareness during general anesthesia that is usually stable at the maintenance period. The aim of this study is to evaluate the incidence of awareness during the induction period of general anesthesia in which the effects of anesthetics are unstable.MethodsThe research-nurses interviewed the patients, who had undergone general anesthesia, on the awareness during anesthesia within a week after operation. The patients were excluded from the study if they were in deep sedation or unconscious because of the medical reasons. We defined the induction period from the administration of hypnotic drugs to the tracheal intubation.ResultsSeven cases with ages from 20 s to 70 s out of 1922 cases were identified as the residual awareness cases during the induction period. Six cases were managed with low concentrations of inhalation anesthetics after injection of intravenous hypnotics. The incidence was lower, but not significant, if they were managed with total intravenous technique. The BIS values were above 60 in all these cases if the monitor was attached.ConclusionsThe incidence of awareness during the induction was 0.36%. We have to pay more attention to the disappearance of the hypnotic effect at the induction period.

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