Intraoperative pelvic nerve stimulation performed under continuous electromyography of the internal anal sphincter.
OBJECTIVE
The aim of this animal study was to investigate the effect of intraoperative pelvic nerve stimulation on internal anal sphincter electromyographic signals in order to evaluate its possible use for neuromonitoring during nerve-sparing pelvic surgery.


METHODS
Eight pigs underwent low anterior rectal resection. The intersphincteric space was exposed, and the internal (IAS) and external anal sphincter (EAS) were identified. Electromyography of both sphincters was performed with bipolar needle electrodes. Intermittent bipolar electric stimulation of the inferior hypogastric plexus and the pelvic splanchnic nerves was carried out bilaterally. The recorded signals were analyzed in its frequency spectrum.


RESULTS
In all animals, electromyographic recordings of IAS and EAS were successful. Intraoperative nerve stimulation resulted in a sudden amplitude increase in the time-based electromyographic signals of IAS (1.0 (0.5-9.0) μV vs. 4.0 (1.0-113.0) μV) and EAS (p < 0.001). The frequency spectrum of IAS in the resting state ranged from 0.15 to 5 Hz with highest activity in median at 0.77 Hz (46 cycles/min). Pelvic nerve stimulation resulted in an extended spectrum ranging from 0.15 to 20 Hz. EAS signals showed higher frequencies mainly in a range of 50 to 350 Hz. However, after muscle relaxation with pancuronium bromide, only the low frequency spectrum of the IAS signals was still present.


CONCLUSIONS
Intraoperative verification of IAS function by stimulation of pelvic autonomic nerves is possible. The IAS electromyographic response could be used to monitor pelvic autonomic nerve preservation.
Kneist
Werner
W
Department of General and Abdominal Surgery, University Medical Centre of the Johannes Gutenberg-University Mainz, Langenbeckstrasse 1, Mainz, Germany. kneist@ach.klinik.uni-mainz.de
Kauff
Daniel W
DW
Rahimi Nedjat
Roman K
RK
Rink
Andreas D
AD
Heimann
Axel
A
Somerlik
Karin
K
Koch
Klaus P
KP
Doerge
Thomas
T
Lang
Hauke
H
D001003:Anal Canal / Q000294:innervation* / Q000601:surgery*; D000818:Animals; D019540:Area Under Curve; D004558:Electric Stimulation; D004566:Electrodes; D004576:Electromyography; D005260:Female; D007430:Intraoperative Care; D008297:Male; D010388:Pelvis / Q000294:innervation* / Q000601:surgery*; D034421:Sus scrofa