Effect of Remimazolam on Transcranial Electrical Motor-evoked Potential in Spine Surgery: A Prospective, Preliminary, Dose-escalation Study

Background: Some anesthetic drugs reduce the amplitude of transcranial electrical motor-evoked potentials (MEPs). Remimazolam, a new benzodiazepine, has been suggested to have little effect on MEP amplitude. This prospective, preliminary, dose-escalation study aimed to assess whether remimazolam is associated with lower MEP amplitude in a dose-dependent manner. Methods: Ten adult patients scheduled for posterior spinal fusion were included in this study. General anesthesia was induced with a continuous infusion of remifentanil and remimazolam. After the patient lost consciousness, the infusion rate of remimazolam was set to 1 mg/kg/h, and the patient underwent tracheal intubation. Baseline MEPs were recorded under 1 mg/kg/h of remimazolam in a prone position. Thereafter, the infusion rate of remimazolam was increased to 2 mg/kg/h, with a bolus of 0.1 mg/kg. Ten minutes after the increment, the evoked potentials were then recorded again. The primary endpoint was the MEP amplitude recorded in the left gastrocnemius muscle at 2 time points. Results: There was no difference in MEP amplitude recorded from the left gastrocnemius muscle before and after increasing remimazolam (median [interquartile range]: 0.93 [0.65 to 1.25] mV and 0.70 [0.43 to 1.26] mV, respectively; P =0.08). The average time from the cessation of remimazolam administration to neurological examination after surgery was 4 minutes using flumazenil. Conclusions: This preliminary study suggests that increasing remimazolam from 1 to 2 mg/kg/h might have an insignificant effect on transcranial electric MEPs.