Abstract
With a small-dose remifentanil, some patients showed no reaction and did not remember it postoperatively. We, therefore, hypothesized that remifentanil may decrease the level of consciousness and/or exhibit amnesic effect when stimulations are avoided. Thirty-patients were divided into two groups: non-stimulation group and stimulation group. Anesthesia was induced with 1 micro-g·kg?1·min?1 of remifentanil using no additional hypnotic agent. In the non-stimulation group, patients were left free from any stimulation except non-invasive blood pressure monitoring. In the stimulation group, patients were asked to follow verbal commands. The level of consciousness was evaluated with electroencephalogram and BIS-value derived from it. In the non-stimulation group, all patients reached the decreased level of consciousness in 5 minutes. In the stimulation group, however, 14 patients were judged to be still conscious. 10 patients could open their mouth at the 5th minute, but 9 of these 10 patients did not remember it postoperatively. In conclusion, remifentanil, with no additional anesthetics, exhibited hypnotic and amnesic effects when stimulations were kept minimal.
Highlights
We experienced several cases of severe muscle rigidity during induction of anesthesia using remifentanil
We observed decrease in Bispectral Index (BIS) value with clear delta waves in the electroencephalogram (EEG) only by 1 micro-g·kg−1·min−1 of infusion of remifentanil in a few minutes since the start of infusion, and those patients commented after surgery that they were unconscious and did not remember the situation during induction of anesthesia
Assuming that BIS value and EEG pattern present the level of consciousness, we investigated the effect of verbal stimulation on the BIS value during induction of anesthesia in order to characterize the hypnotic and amnesic effect of remifentanil
Summary
We experienced several cases of severe muscle rigidity during induction of anesthesia using remifentanil. We observed decrease in Bispectral Index (BIS) value with clear delta waves in the electroencephalogram (EEG) only by 1 micro-g·kg−1·min−1 of infusion of remifentanil in a few minutes since the start of infusion, and those patients commented after surgery that they were unconscious and did not remember the situation during induction of anesthesia. We hypothesized that remifentanil may have hypnotic and amnesic effect and may decrease the level of consciousness, and verbal stimulation may attenuate this hypnotic effect. Assuming that BIS value and EEG pattern present the level of consciousness, we investigated the effect of verbal stimulation on the BIS value during induction of anesthesia in order to characterize the hypnotic and amnesic effect of remifentanil
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