Partial neuromuscular blockage levels with mivacurium during mastoidectomy allows intraoperative facial nerve monitoring.

BACKGROUND: Facial nerve monitoring during otologic surgery is helpful for facial nerve preservation, but its usage is closely related to anesthetic procedures.

OBJECTIVES: The aim of this study was to investigate the effectiveness of mivacurium-based partial neuromuscular blockade on facial nerve monitoring during otologic surgery.

METHODS: Forty-three patients scheduled for elective otologic surgery (mastoidectomy with and without tympanoplasty) participated in the study. After induction with propofol 2-3 mg x kg(-1), remifentanil 1 microg x kg(-1) and mivacurium 0.2 mg x kg(-1), anesthesia was maintained with isoflurane 0.6-1.6 minimum alveolar concentration and remifentanil 0.25 microg x kg(-1) x min(-1). Following complete recovery of neuromuscular blockade during induction, mivacurium infusion was initiated at 6 microg x kg(-1) x min(-1) in an adjusted dose to reflect adductor pollicis activity of 50, 75 or 100% of normal. The minimum stimulation thresholds obtained from each case were recorded.

RESULTS: Pre- and postoperatively, all 43 patients demonstrated clinically normal facial nerve function. In all cases, intraoperative facial nerve monitoring was performed successfully. There were no differences in threshold levels of the facial nerve stimulation between group I (1.84 +/- 0.4 mA ) and group II (1.97 +/- 0.2 mA). However, the stimulation thresholds of group III (1.53 +/- 0.4 mA ) were found to be lower than those of groups I and II (p < 0.05).

CONCLUSION: We conclude that partial neuromuscular blockade with mivacurium permits intraoperative facial nerve monitoring.