Effect Of Current Stimulation Of Intraoperative Nerve Monitoring On Vagus Nerve And Recurrent Laryngeal Nerve In Rabbits

Objective:In this study,we preliminarily investigated the effects of intraoperative nerve monitoring current stimulation on the vagus nerve(VN)and recurrent laryngeal nerve(RLN)of rabbits,and observed the changes of nerve electromyography(EMG)amplitude,latency,electrocardiogram(ECG)and histological changes,so as to determine the safety and reliability of current stimulation on nerves.The distance of effective nerve electromyography(EMG)induced by the stimulus point was measured under different current intensities,namely "current radiation distance".The position and course of the vagus nerve and recurrent laryngeal nerve can be accurately determined according to the current radiation distance under different current intensities,which is beneficial to nerve exploration and anatomy.Methods:The rabbits were dissected to expose one side of the vagus nerve and the contralateral recurrent laryngeal nerve,and the vagus nerve and the contralateral recurrent laryngeal nerve were stimulated with 1-30 m A current,respectively.The amplitude and latency of nerve electromyography,ECG changes and histological changes were observed to evaluate the degree of nerve tolerance to stimulation current,the integrity of nerve function and the safety of current.The effective nerve electromyography(EMG)was induced by stimulating the vagus nerve andrecurrent laryngeal nerve with different current intensity.By measuring the distance between the probe stimulation point and the nerve,the current radiation distance corresponding to the current was determined.Results:The EMG latency,amplitude and waveform of recurrent laryngeal nerve and vagus nerve were stable after 1-30 m A current stimulation,indicating that the current stimulation had no effect on the integrity of nerve function.Before and after 1-30 m A current stimulation,there were no significant changes in ECG,heart rate,and R-R interval,indicating that cardiac electrophysiology was stable.The vagus nerve and recurrent laryngeal nerve of rabbits were stimulated with 1-15 m A current.Histological light microscopy showed normal structure of nerve fiber myelin sheath and axon,without interruption of nerve continuity,disorder of microcirculation or hemorrhage,degeneration or necrosis of nerve cells,and no obvious damage to the blood vessels in the nerve,i.e.no injury.The vagus and recurrent laryngeal nerves of rabbits were stimulated with 20-30 m A current.Slight epineurium edema and nonspecific diffuse white blood cells in the epineurium were observed histologically.It indicates that at 20-30 m A current intensity,the nerve function is intact,with microscopic nerve injury.In the experiment,it was measured that when1 m A,2m A and 3m A current were given to stimulate the vagus nerve and the recurrent laryngeal nerve,the corresponding current radiation distance was the same,which was 1mm,3mm and5 mm respectively.When 5m A was administered to stimulate the vagus nerve,the current radiation distance was 10 mm.When 5m A current is given to stimulate the recurrent laryngeal nerve,the current radiation distance is not reliable.When the current was stimulated above 5m A,the current radiation distance could not be measured because the current intensity was too large,which caused a wide range of current radiation reactions in the surrounding nerve tissues.Conclusion:The vagus nerve and recurrent laryngeal nerve of rabbits were stimulated with 1-15 m A current intensity.The nerve function was intact,the heart was electrophysiologically stable,and there was no sign of nerve injury in texture.The current stimulation below 15 m A was safe.The nerve function is complete,the heart is electrophysiologically stable,and there is no sign of nerve injury in texture.The vagus nerve and recurrent laryngeal nerve of rabbits were stimulated with20-30 m A current intensity.The nerve function was intact,but the histological manifestations of nerve injury were observed.The current of 1m A,2m A and 3m A was given to stimulate the vagus nerve and the recurrent laryngeal nerve of rabbits,and the corresponding current radiation distance was the same,1mm,3mm and 5mm,respectively.The current radiation distance of the vagus nerve stimulated by 5m A was 10 mm.The current radiation distance of 5m A to stimulate therecurrent laryngeal nerve is not reliable.The current radiation distance could not be measured by stimulating the vagus nerve and recurrent laryngeal nerve with a current of more than 5m A.