Effect of Halothane Anesthesia on the Human Cortical Visual Evoked Response

Abstract

The visual evoked response (VER) was monitored in 8 women intraoperatively during anesthesia with halothane in O2 administered via endotracheal tube. Control measurements were made prior to anesthetic induction in these unpremedicated patients. The latency of the positive peak designated P1 increased progressively from a mean of 113 .+-. 10 (SD) ms in the awake state to the following values at indicated end-tidal halothane concentrations: 123 .+-. 10 ms at 0.75% 130 .+-. 9 ms at 0.90%; 134 .+-. 9 ms at 1.13%. The differences among mean latency values at these anesthetic concentrations were insufficient to conclude that VER latency would be a useful monitor of anesthetic depth. Significant effects were seen at clinical levels of halothane anesthesia and the prolongation due to anesthesia must be considered when using VER to monitor CNS function during neurosurgery.