Effect of total intravenous anesthesia versus sevoflurane anesthesia on intraoperative facial nerve monitoring: a randomized controlled trial

Purpose: Intraoperative facial nerve monitoring (IFNM) facilitates effective nerve preservation during ear and head and neck surgeries. Quantitative differences in the timely feasibility of IFNM during total intravenous anesthesia (TIVA) vs sevoflurane anesthesia have not been investigated. Methods: We conducted a randomized controlled trial in which 98 patients undergoing ear surgery were allocated to either the TIVA or sevoflurane group. We used quantitative neuromuscular monitoring of train-of-four (TOF) responses to assess achievements of IFNM-feasible conditions, and recorded the TOF count (TOFC) or TOF ratio of T4/T1 (TOFR). The primary outcome was the time interval between a TOFR of 0.25 and 0.75 (recovery index). The most important secondary outcome was the time to reach a TOFR of 0.25. We also recorded the quality of IFNM, intubation condition, patient-ventilator dyssynchrony, surgeon’s satisfaction, and postoperative analgesic and antiemetic requirements. Results: Ninety-two patients completed the study. The median [interquartile range] recovery index was significantly shorter in the TIVA group (9 [7–11] min) than in the sevoflurane group (34 [24–53] min), with a difference in medians of 25 min (95% confidence interval, 20 to 31; P < 0.001). Before IFNM requests, the time to TOFR of 0.25 was achieved earlier in the TIVA group (34 [29–41] min) than in the sevoflurane group (51 [43–77] min) (P < 0.001). Both groups achieved neuromuscular recovery in time for IFNM without a need for reversal agents. Conclusions: Intraoperative facial nerve monitoring was feasible earlier and faster under TIVA than under sevoflurane anesthesia. We suggest that TIVA may be a preferable choice over sevoflurane to meet a surgeon’s request for an earlier IFNM. Study registration: CRIS.nih.go.kr (KCT0006676); first submitted 7 October 2021.