The long-latency auditory evoked potential as a measure of the level of consciousness during sufentanil anesthesia.

The long-latency auditory evoked potential was recorded during opioid anesthesia to evaluate its usefulness for assessing the level of consciousness. Eight patients undergoing coronary artery surgery under high-dose sufentanil anesthesia following a lorazepam premedication were tested. Four waves were studied: the N1, P2, P3, and the slow wave (SW). The amplitude of N1 and that of the SW were reduced by sufentanil, but the differences did not reach significance. The amplitude and latency of P2 and the latency of the SW were significantly reduced. The P3, which is possibly a specific indicator for consciousness, was present before induction and absent during anesthesia. There was no conscious recall for intraoperative events. Preservation of the N1, P2, and SW, which are abolished by nonopioid general anesthetics, suggests that auditory processing proceeds further during anesthesia with sufentanil. However, no electrophysiologic evidence of consciousness was found during sufentanil anesthesia.