Electromyographic response of facial nerve stimulation under different levels of neuromuscular blockade during middle-ear surgery

Abstract

Objective: To investigate facial nerve monitoring in patients receiving the partial nondepolarizing neuromuscular blocking agents (NMBAs), remifentanil and propofol. Methods: Patients with normal facial function and advanced middle-ear disease were enrolled. For total intravenous anaesthesia (TIVA), propofol and remifentanil were infused as induction/ maintenance anaesthesia. Stimulation thresholds and amplitudes were recorded at each train-offour (TOF) nerve stimulation level. Time differences between start of TOF and electromyographic (EMG) amplitude decreases (Ti), and between complete recovery of TOF and EMG amplitudes (Tr), were calculated. Results: Fifteen patients were enrolled. Mean AE SD Ti was 3.4 AE 1.28 min; Tr was 18.7 AE 4.41 min. Amplitude of stimulation was apparent mostly at TOF level 1. In most cases, no or a weak response (<100 mV) was observed at TOF 0. Mean AE SD threshold of electrical stimulation was 0.31 AE 0.10 mA at TOF 1. At TOF > 2, all cases showed EMG response on electrical stimulation. Conclusions: Induction of TIVA using propofol and remifentanil provided reliable conditions for delicate microsurgery. Minimal NMBA use, considered as producing TOF levels >1, was sufficient for facial nerve monitoring in neuro-otological surgery.

Facial Nerve Intraoperative Monitoring in Otologic Surgeries under Sedation and Local Anesthesia – A Case Series and Literature Review

“…Greater doses of propofol, however, lead to a significant negative effect in the FNIM. 24,25 Classically, the administration of neuromuscular blocking agents is thought to be detrimental to intraoperative nerve monitoring, as they act directly in the neuromuscular junction. Choe et al 25 have showed, nonetheless, that during TIVA by combing propofol and remifentanil, the controlled use of nondepolarizing neuromuscular blocking agents would not hinder facial nerve monitoring.…”

“…24,25 Classically, the administration of neuromuscular blocking agents is thought to be detrimental to intraoperative nerve monitoring, as they act directly in the neuromuscular junction. Choe et al 25 have showed, nonetheless, that during TIVA by combing propofol and remifentanil, the controlled use of nondepolarizing neuromuscular blocking agents would not hinder facial nerve monitoring. 24 Halogenated volatile compounds might completely abolish neuroelectrophysiological responses, and are, therefore, not routinely used when intraoperative nerve monitoring is considered during the surgery.…”

Anaesthesia for major middle ear surgery

“…a train-offour count of 3 or 4) does not appear to affect the ability of the facial nerve monitor to function. 13 An alternative option is to avoid neuromuscular blockade entirely; however, neuromuscular blockade-free intubation techniques in adults can increase the risk of haemodynamic instability, poor intubating conditions, and postoperative airway discomfort. 14 Nitrous oxide is typically avoided because of its ability to diffuse into the non-compliant middle ear cavity faster than nitrogen diffuses out.…”