Anesthetic Fade in Intraoperative Transcranial Motor Evoked Potential Monitoring Is Mainly due to Decreased Synaptic Transmission at the Neuromuscular Junction by Propofol Accumulation

Satoshi Tanaka; Kenta Yamamoto; Shinsuke Yoshida; Ryosuke Tomio; Takeshi Fujimoto; Misuzu Osaka; Toshio Ishikawa; Tsunemasa Shimizu; Norio Akao; Terutaka Nishimatsu

doi:10.1055/a-2103-7381

Anesthetic Fade in Intraoperative Transcranial Motor Evoked Potential Monitoring Is Mainly due to Decreased Synaptic Transmission at the Neuromuscular Junction by Propofol Accumulation

J Neurol Surg A Cent Eur Neurosurg. 2023 Dec 19. doi: 10.1055/a-2103-7381. Online ahead of print.

Affiliations

¹ Department of Neurosurgery, Numata Neurosurgery & Cardiovascular Hospital, Numata, Gunma, Japan.
² Department of Clinical Laboratory, Numata Neurosurgery & Cardiovascular Hospital, Numata, Gunma, Japan.
³ Department of Neurosurgery, Saitama Medical Center, Kawagoe, Saitama, Japan.
⁴ Department of Neurosurgery, Honjo Neurosurgery & Spinal Surgery Clinic, Honjo, Saitama, Japan.

PMID: 37257841
DOI: 10.1055/a-2103-7381

Abstract

Background: We previously reported that normalization of motor evoked potential (MEP) monitoring amplitude by compound muscle action potential (CMAP) after peripheral nerve stimulation prevented the expression of anesthetic fade (AF), suggesting that AF might be due to reduced synaptic transfer in the neuromuscular junction.

Methods: We calculated the time at which AF began for each of craniotomy and spinal cord surgery, and examined whether AF was avoided by CMAP after peripheral nerve stimulation normalization in each. Similar studies were also made with respect to the upper and lower limb muscles.

Results: AF was observed in surgery lasting 160 minutes for craniotomy and 260 minutes or more for spinal surgery, and 195 minutes in the upper limb muscles and 135 minutes in the lower limb muscles. In all the series, AF could be avoided by CMAP after peripheral nerve stimulation normalization.

Conclusion: AF of MEP occurred in both craniotomy and spinal cord surgery, and it was also corrected by CMAP after peripheral nerve stimulation. AF is considered to be mainly due to a decrease in synaptic transfer of the neuromuscular junction due to the accumulation of propofol because of the avoidance by CMAP normalization. However, it may be partially due to a decrease in the excitability of pyramidal tracts and α-motor neurons, because AF occurred earlier in the lower limb muscles than in the upper limb muscles.