[The effects of halothane and nitrous oxide on transcranial magnetic evoked potentials]

The influence of volatile anaesthetic agents on transcranial magnetic motor evoked potentials (TMEP) is not known. The effect of halothane and nitrous oxide on TMEP as recorded from hand was studied in 10 patients undergoing lumbar spinal surgery. In no case were the TMEP documented when halothane and nitrous oxide were administered. After withdrawal of both agents it took up to 29 minutes until the TMEP reappeared. It is concluded that intraoperative monitoring of TMEP is not possible if halothane and nitrous oxide are administered.