Intraoperative neurophysiological monitoring for inhalational anesthesia based on the minimum alveolar concentration level

Abstract

Total intravenous anesthesia (TIVA) is regard as a gold standard for intraoperative neurophysiological monitoring (IONM). Meanwhile, TIVA could induce a substantial reduction of cerebral blood volume and affect to hemodynamic and cardiovascular parameters. Inhalational anesthetics have relatively smaller impact on patients than intravenous anesthesia. But it could affect IONM modality especially in motor evoked potentials (MEP). We experienced four cases with inhalational anesthesia in IONM. According to minimum alveolar concentration (MAC) level, the amplitude of MEP changed. In 1.0 MAC, the wave form of MEP were not recognizable. But when we maintained total MAC of 0.5, we could obtain reliable MEPs and SSEPs. Inhalational anesthetics could inhibit the pyramidal activation of spinal motor neurons and synaptic transmission in the cerebral cortex. Based on our experiences, in the case with unstable hemodynamic state or contraindication to intravenous anesthesia, inhalational anesthesia with MAC 0.5 could be an alternative option.