Effects of sevoflurane on transcranial electrical motor evoked potential monitoring elicted from four-limb muscles

Objective To compare the influence of different end-tidal concentrations of sevoflurane on transcranial electrical four-limb muscle motor evoked potential (MEP) monitoring. Methods Twenty ASA Ⅰ-Ⅱpatients aged 23-62 years undergoing craniotomy were enrolled. Triangular muscle, biceps brachii muscle, triceps brachii muscle, brachioradialis muscle, extensor digitorum communis muscle, abductor pollicis brevis abductor digiti minimi muscle, rectus femoris muscle, tibialis anterior muscle, gastrocnemius muscle and abductor hallucis were selected for MEPs recording. Sevoflurane was introduced at 0.5, 0.75, 1.0 and then 1.3 MAC (15 min each), and the effects on MEPs were studied. Results ①Maximum MEP amplitude was observed at abductor pollicis brevis muscle in upper limb and abductor hallucis muscle in lower limb at baseline and 0.5 MAC. Up to 1.0 MAC, there was no significant difference in MEP amplitude among extensor digitorum communis muscle, abductor pollicis brevis and abductor digiti minimi muscle. ②The success rate of MEP recording from abductor pollicis brevis muscle and abductor hallucis muscle was 100% during the administration of 0.5-1.0 MAC sevoflurane. ③The MEP amplitude was decreased and the latency was increased in a sevoflurane dose-dependent manner. Conclusions Abductor pollicis brevis muscle and abductor hallucis muscle were suitable for MEP monitoring during the administration of 0.5-1.0 MAC sevoflurane.