[Effects of isoflurane, sevoflurane and enflurane on median nerve somatosensory evoked potentials in humans].

Median nerve somatosensory evoked potentials (SEPs) were recorded over neck (N13) and scalp (N20) in 18 neurologically normal subjects anesthetized with isoflurane, sevoflurane or enflurane for abdominal or lower limb surgery. SEP recordings were made at 0.5, 1.0 and 1.5 MAC of each volatile agent without nitrous oxide. These three agents did not change N13 latency and amplitude. Increasing concentrations of isoflurane and sevoflurane were associated with graded reductions in N20 amplitude and increases in N20 latency and N13-N20 interpeak latency. During enflurane anesthesia N20 amplitude was smaller than that at increased in dose related manner. At 1.0 MAC of enflurane N20 amplitude was smaller than that at 0.5 MAC, but further decrease was not produced at 1.5 MAC. The data suggest that effects of sevoflurane on SEPs were more similar to those of isoflurane than those of enflurane.