[Alterations of the brain stem and mid-latency evoked potentials under oxygen-nitrous oxide-sevoflurane anesthesia].

We evaluated the alterations of the brain stem and mid-latency evoked potentials (BAEP and MLAEP) in 10-patients who were scheduled for elective abdominal surgery under oxygen-nitrous oxide-sevoflurane anesthesia. With oxygen 2 l.min-1 and nitrous oxide 4 l.min-1, we measured the latency of BAEP and MLAEP at the end-expired sevoflurane concentrations of 0%, 0.3%, 0.6%, 1.0%, 1.5% and 2.0%, respectively. The latency of BAEP was slightly prolonged with oxygen-nitrous oxide-sevoflurane anesthesia. The latency of MLAEP was markedly prolonged with the increase of sevoflurane concentration, and all waves but Na wave disappeared at the 2.0% sevoflurane concentration.