Effects of halothane on motor evoked potential recorded in the extradural space

We studied the effects of supplementing nitrous oxide-oxygen anaesthesia with halothane (1 MAC end-tidal concentration) on the motor evoked potential recorded in the extradural space of eight patients before corrective surgery for idiopathic adolescent scoliosis. The motor cortex was stimulated electrically through the scalp. An additional eight patients in whom anaesthesia was supplemented with an infusion of propofol acted as a control group. Halothane had no significant effect on the amplitude or latency of the motor evoked potential. We conclude that halothane is unlikely to alter the interpretation of motor evoked potentials recorded extradurally during scoliosis surgery.