刺激次数对术中运动诱发电位监测的影响

The effects of multiple stimuli on intraoperative monitoring of motor-evoked potentials

目的观察多次刺激模式对全麻下经颅磁刺激运动诱发电位(tcMMEPs)的影响。方法20例择期行脊髓手术的病人,在麻醉前后分别记录tcMMEPs在单次、2次和4次刺激下的波幅、潜伏期和阈值,2次和4次模式的刺激间隔均为2ms。结果麻醉后各种刺激模式的波幅都比麻醉前有极显著降低(P<0.01);但随着刺激次数的增加,波幅逐渐增大(P<0.01)。麻醉后各种刺激模式的刺激阈值都比麻醉前显著升高(P<0.01),但随着刺激次数的增加,阈值逐渐下降(P<0.01)。在麻醉后行单次刺激时,只有3例病人能引出tcMMEPs;2次刺激时有15例病人能引出tcMMEPs。在麻醉前后各刺激模式下的潜伏期都无显著变化。结论麻醉药显著抑制单次tcMMEPs的波幅,提高兴奋阈值;而2次和4次刺激在麻醉状态下能显著升高被抑制的波幅,降低兴奋阈值,部分对抗麻醉药的抑制作用,4次刺激的这种作用比2次更强。在麻醉状态下行tcMMEPs监测时应选用2次以上的刺激模式来增加监测的准确性。

Objective To evaluate the effects of multiple stimuli on magnetic transcranial motor-evoked potentials（tcMMEPs） under general anesthesia. Methods Twenty patients undergoing elective spinal surgery were stimulated by single, double and quadruple magnetic transcranial stimulation before and after anesthesia. The inter-stimulus intervals of double and quadruple stimulation were 2 ms. The amplitude,latency and threshold were recorded respectively. Results The amplitude of each stimulation pattern after anesthesia was significantly decreased compared to that before anesthesia （P〈0.01）. But the amplitude increased in company with the increase of the number of stimulation （P〈0.01）. The threshold of each stimulation pattern after anesthesia was significantly increased compared to that before anesthesia （P〈0.01）. But the threshold decreased in company with the increase of the number of stimulation （P〈0.01）. tcMMEPs were induced only in 3 patients with single stimulation pattern and in 15 patients with double stimulation pattern. The latency of all stimulation patterns was not significantly changed after anesthesia. Conclusion With single stimulation pattern, anesthetics inhibited the amplitude and increased the threshold of tcMMEPs, which could be partially antagonized by double and quadruple stimulation patterns. We suggest that more than two stimuli should be chosen during tcMMEPs monitoring under general anesthesia.