刺激参数对经颅电刺激运动诱发电位的影响

目的：评价不同刺激参数对经颅电刺激运动诱发电位（MEPs）监测的影响,为临床进行MEPs监测提供参考。方法：选取神经外科择期手术患者18例,年龄23～64岁。美国麻醉医师学会（ASA）分级Ⅰ～Ⅱ级。采用经颅电刺激技术记录MEPs,患者采用丙泊酚和瑞芬太尼全凭静脉麻醉。选择拇短展肌作为记录肌肉。分别给于不同的刺激强度（100、200、300、400和500V）、刺激频率（100、200、500和1000Hz）和脉冲数（2、3、4、5和6个）时记录MEPs的波幅和潜伏期。不同刺激参数对MEPs波幅和潜伏期的影响采用重复测量方差分析。结果：①刺激强度≥300V,刺激频率≥500Hz以及脉冲数≥3个时的MEPs记录成功率为100%。②刺激频率和脉冲数可显著影响MEPs的波幅（P值均〈0.01）,以刺激频率的影响更为显著;刺激强度对MEPs波幅的影响不显著。刺激频率可显著影响MEPs的潜伏期（P〈0.001）;刺激强度和脉冲数对MEPs潜伏期的影响不显著。③随刺激频率的增高,MEPs波幅呈显著增高趋势,潜伏期呈显著下降趋势;脉冲数5和6个时记录的MEPs波幅最高;不同刺激强度记录的MEPs波幅和潜伏期的差异无统计学意义。④最佳刺激参数为刺激强度300V,刺激频率1000Hz,脉冲数6个。结论：刺激频率是影响MEPs波幅的最主要因素;选择合适的刺激参数可显著提高MEPs的波幅。

The Effects of Stimulation Pattern on Transcranial Electrical Motor Evoked Potentials

Objective：To investigate the effects of different stimulation patterns on intra-operative transcranial electrical motor evoked potentials（MEPs）.Methods：Eighteen ASA Ⅰ-Ⅱpatients aged 23-64 years undergoing craniotomy were enrolled. Stimulation patterns including intensity,frequency and number of stimuli were varied randomly while propofol and remifentanil was administered at a constant rate. The amplitudes and latency were recorded by abductor pollicis brevis muscle. Repeated measures anova was used to analyze the effects of stimulation patterns on MEPs.Results：①The success rates of MEPs recording was 100% during 3 to 6 stimuli delivered at 500-1000 Hz and 300-500 V. ②The significant effects for increasing frequency and number of stimuli on MEPs amplitude were observed （P0.001）.The effect of intensity on the MEPs amplitude was not significant. MEPs latency varied significantly with changes in frequency and less so with changes in intensity and number of stimuli. ③The higher MEPs amplitude was observed in frequency 1000 Hz and from 5 to 6 stimuli. There was no significant difference among different intensity for the MEPs amplitudes. ④Maximum MEPs amplitudes and recording success rates were observed during 6 stimuli delivered at 1000 Hz and 300 V. Conclusions：The stimulation frequency plays an important role in the MEPs characteristics. The results suggest that the suitable stimulation pattern allow intraoperative use of MEPs monitoring.