甲状腺及甲状旁腺手术中迷走神经及喉返神经适宜刺激电流强度的探讨

Exploration of Optimal Current Intensity for Neural Monitoring of Vagus Nerve and Recurrent Laryngeal Nerve During The Thyroid and Parathyroid Surgery

目的探索甲状腺及甲状旁腺手术中迷走神经及喉返神经标准化监测各步骤的适宜刺激电流强度,以便更有效、更快速地对神经进行功能判断、定位、辨识及保护。方法前瞻性收集2013年5月至2013年8月期间在四川大学华西医院甲状（旁）腺疾病诊治中心接受同一主刀医师手术治疗并使用IONM的100例甲状腺或甲状旁腺疾病患者的临床资料,其中有损伤风险的喉返神经为186条。按标准化神经监测流程,用1-5 mA和1-3 mA的电流强度分别间接和直接刺激迷走神经及喉返神经,记录其肌电信号振幅以及监测刺激过程中患者的心率及血压变化情况,来寻求术中神经监测各阶段最适宜的电流强度。结果颈动脉鞘外监测迷走神经信号时,186条受测迷走神经中,1 mA时有109条（58.6%）有信号,得到稳定的肌电图及提示音,2 mA时有164条（88.2%）有信号,3 mA时有177条（95.2%）有信号,5 mA时有182条（97.8%）有信号;且在神经电刺激前后,患者的心率和血压均无明显变化。直接探测迷走神经时,1 mA监测V1信号时有2条（1.1%）无应答,V2时有9条（4.8%）无应答,而2 mA和3 mA的电流刺激时均得到了稳定的肌电信号。定位寻找喉返神经时,1 mA时有92条（49.5%）有信号,2 mA时有171条（91.9%）有信号,3 mA时有184条（98.9%）有信号。当鉴别喉返神经时,用2 mA的电流强度刺激,会出现电流旁传导而产生假象;以1 mA的电流刺激强度时,探针置于喉返神经邻近组织时则无肌电信号。鉴别RLN各分支时,用1 mA的电流强度刺激各神经分支,均可以得到肌电信号,其中入喉的主干分支振幅最高,支配食管及气管的分支肌电图振幅数值相近,为主干振幅数值的1/3-1/4。结论建议用5 mA的电流强度在颈鞘表面间接监测迷走神经以得到V1信号,可替代剖开颈鞘直接监测迷走神经的步骤;如鞘外监测V1信号失败,再解剖颈鞘,用3 mA的电流强度来直接监测迷走神经;用3 mA的电流强度寻找定位喉返神经;用1 mA的电流强度来鉴别喉返神经及其食管分支、气管分支、血管等。

Objective To explore optimal current intensity for neural monitoring of vagus nerve and recurrent laryngeal nerve during the thyroid and parathyroid surgery, so that we can judge function, location, identify, and protect the nerve more effectively and more quickly. Methods A total of 100 patients who underwent thyroid or parathyroid operations by the same surgeon in West China Hospital, meanwhile accepted intraoperative neuromonitoring（IONM）, and 186 nerves at risk were enrolled in this study. According to the standardized process of nerve monitoring, we stimulated the vagus nerve with the current strength of 1-5 mA, and respectively stimulated laryngeal recurrent nerve with 1-3 mA indirectly and directly, and recorded the amplitude of electromyographic signal, and changes of heart rate and blood pressure during the process. The purpose was seeking the optimum current strength for each stage of IONM. Results In 186 vagus nerves being tested, when monitoring the vagus nerve outside the carotid sheath, 109 vagus nerves（58.6%） sent out signals and got stable electromyography and warning tone with 1 mA, 164（88.2%） vagus nerves had signals with 2 mA, 177（95.2%） vagus nerves had signals with 3 mA, 182（97.8%） vagus nerves had signals with 5 mA.Before and after the vagus nerve stimulation, heart rate and blood pressure of patients had no significant change. When directly monitoring the vagus nerve with 1 mA, V1 signals had no response in 2 vagus nerves（1.1%）, V2 signals had no response in 9 vagus nerves（4.8%）. But if the current intensity of stimulation was 2 mA or 3 mA, all patients got stable electromyographic signals. When searching for the laryngeal recurrent nerve, 92（49.5%） got signals with 1 mA, 171（91.9%） got signals with 2 mA, 184（98.9%） got signals with 3 mA. When identifying laryngeal recurrent nerve and others, if the intensity of current was more than 2 mA, the current might conduct around and produce illusion. However, if the intensity of stimulation current was 1 mA, there’s no electromyographic signal when we put the probe onto the tissue close to the laryngeal recurrent nerve. During identification of branches of laryngeal recurrent nerve with current strength of 1 mA, each electromyographic signal could be obtained. The chief branch into the throat produced the highest amplitude. The esophagus and trachea branch emg amplitude value was similar, equalling to 1/3-1/4 of the amplitude value in chief branch. Conclusions We suggest using current intensity of 5 mA on the surface of the carotid sheath to monitor the vagus nerve indirectly and obtain V1 signal, as an alternative to opening the carotid sheath. If fail, dissecting the carotid sheath, and using current intensity of 3 mA to monitor the vagus nerve directly; 3 mA is the optimal current intensity to search for the laryngeal recurrent nerve, and 1 mA is the optimal current intensity to identify the laryngeal recurrent nerve and its branches of esophagus and trachea, blood vessels, and so on.