Effects of rocuronium dosage on intraoperative neurophysiological monitoring in patients undergoing spinal surgery

What is known and objective Intraoperative neurophysiological monitoring (IONM) has been widely used in clinical practice. Therefore, the influence of neuromuscular blockers essential for spinal anaesthesia on IONM is worthy of our attention, but no randomized study has evaluated the dose-response effect. This study investigated the effects of different doses of rocuronium bromide on the intraoperative monitoring of motor evoked potentials (MEPs). Methods We conducted a randomized, double-blind trial to assess the effects of three rocuronium bromide doses (6.0, 9.0, 12 mu g center dot kg(-1)center dot min(-1)) combined with intravenous infusion of propofol 6-8 mg center dot kg(-1)center dot h(-1) and remifentanil 10 mu g center dot kg(-1)center dot h(-1) on the amplitudes of somatosensory evoked potentials (SEPs) and MEPs at the time of the baseline recording (T-1), before pedicle screw placement (T-2) and before spinal canal decompression (T-3). Secondary outcomes included measurement of neuromuscular function, the occurrence of unexpected intraoperative body movement and recovery of spontaneous breathing. Results and discussion A total of 123 patients were enrolled, and 120 patients were ultimately analysed. No differences were observed in the amplitude of SEPs among the three groups (p > 0.05). The MEP amplitude differences at T-1, T-2 and T-3 in all limbs did not differ in patients receiving rocuronium at 6.0 mu g center dot kg(-1)center dot min(-1) and 9.0 mu g center dot kg(-1)center dot min(-1) (p > 0.05). However, when rocuronium was administered at 12.0 mu g center dot kg(-1)center dot min(-1), MEP amplitudes at the time point T-3 were significantly attenuated compared with the time points T-1 and T-2 in both right upper limb and left lower limb (p = 0.002, p = 0.025, respectively). In patients treated with rocuronium 6.0 mu g center dot kg(-1)center dot min(-1), the incidence of unexpected body movement was significantly higher (p = 0.026), and the train-of-four count (TOF count) showed a significant increase at T-2 and T-3 (p < 0.001) compared to other doses. What is new and conclusion Rocuronium bromide at a rate of 9.0 mu g center dot kg(-1)center dot min(-1) provided suitable and adequate muscle relaxation without inhibiting IONM; thus, this dose is recommended for spinal surgery.