Department of Occupational Therapy, School of Health and Medical Sports, Teikyo Heisei University, Ichihara-city, Chiba, Japan.
Departments of Neurosurgery and.
J Clin Neurophysiol. 2021 Jul 1;38(4):306-311. doi: 10.1097/WNP.0000000000000692.
Anesthetic fade refers to the time-dependent decrease in the amplitude of the intraoperative motor-evoked potential. It is thought to be caused by the accumulation of propofol. The authors examined whether normalization by the compound muscle action potential (CMAP) after peripheral nerve stimulation could compensate for anesthetic fade.
In 1,842 muscles in 578 surgeries, which did not exhibit a motor-neurologic change after the operation, the motor-evoked potential amplitude was normalized by the CMAP amplitude after peripheral nerve stimulation, and the CMAP amplitude and operation times were analyzed.
The amplitudes of both motor-evoked potential and CMAP increased over time after peripheral nerve stimulation because of the disappearance of muscle-relaxant action. Especially, after peripheral nerve stimulation, CMAP significantly increased from the beginning to the end of the operation. Anesthetic fade in transcranial motor-evoked potential monitoring seemed to occur at more than 235 minutes of surgery based on the results of a receiver operating characteristic analysis of the operation time and relative amplitudes. Although the mean amplitude without CMAP normalization at more than 235 minutes was significantly lower than that at less than 235 minutes, the mean amplitude with normalization by CMAP after peripheral nerve stimulation at more than 235 minutes was not significantly different from that at less than 235 minutes.
Compound muscle action potential after peripheral nerve stimulation normalization was able to avoid the effect of anesthetic fade. Anesthetic fade was seemed to be caused by a decrease in synaptic transmission at the neuromuscular junction because of propofol accumulation by this result.
麻醉消退是指术中运动诱发电位幅度随时间的下降。它被认为是由丙泊酚的积累引起的。作者研究了外周神经刺激后的复合肌肉动作电位（CMAP）归一化是否可以补偿麻醉消退。
在 578 例手术的 1842 块肌肉中，术后未出现运动神经功能改变，通过外周神经刺激后的 CMAP 幅度对运动诱发电位幅度进行归一化，并对 CMAP 幅度和手术时间进行分析。
由于肌肉松弛作用的消失，外周神经刺激后运动诱发电位和 CMAP 的幅度随时间增加。特别是，外周神经刺激后，CMAP 从手术开始到结束显著增加。基于手术时间和相对幅度的接收者操作特征分析结果，似乎在 235 分钟以上的手术中出现经颅运动诱发电位监测的麻醉消退。尽管在超过 235 分钟时不进行 CMAP 归一化的平均幅度明显低于在 235 分钟以下时，但在超过 235 分钟时通过外周神经刺激后的 CMAP 归一化后的平均幅度与在 235 分钟以下时没有显著差异。
外周神经刺激后的复合肌肉动作电位归一化能够避免麻醉消退的影响。由于丙泊酚的积累导致突触在神经肌肉接头处的传递减少，因此产生了这种结果，麻醉消退似乎是由其引起的。
