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-of-four (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 ± SD Ti was 3.4 ± 1.28 min; Tr was 18.7 ± 4.41 min. Amplitude of stimulation was apparent mostly at TOF level 1. In most cases, no or a weak response (<100 µV) was observed at TOF 0. Mean ± SD threshold of electrical stimulation was 0.31 ± 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.
Keywords: Facial nerve; electromyography; monitoring; neuro-otological surgery; propofol; remifentanil train-of-four; total intravenous anaesthesia.