Magnesium Sulfate Enables Patient Immobilization during Moderate Block and Ameliorates the Pain and Analgesic Requirements in Spine Surgery, Which Can Not Be Achieved with Opioid-Only Protocol: A Randomized Double-Blind Placebo-Controlled Study

Spine surgery is painful despite the balanced techniques including intraoperative and postoperative opioids use. We investigated the effect of intraoperative magnesium sulfate (MgSO(4)) on acute pain intensity, analgesic consumption and intraoperative neurophysiological monitoring (IOM) during spine surgery. Seventy-two patients were randomly allocated to two groups: the Mg group or the control group. The pain intensity was significantly alleviated in the Mg group at 24 h (3.2 ± 1.7 vs. 4.4 ± 1.8, p = 0.009) and 48 h (3.0 ± 1.2 vs. 3.8 ± 1.6, p = 0.018) after surgery compared to the control group. Total opioid consumption was reduced by 30% in the Mg group during the same period (p = 0.024 and 0.038, respectively). Patients in the Mg group required less additional doses of rocuronium (0 vs. 6 doses, p = 0.025). Adequate IOM recordings were successfully obtained for all patients, and abnormal IOM results denoting warning criteria (amplitude decrement >50%) were similar. Total intravenous anesthesia with MgSO(4) combined with opioid-based conventional pain control enables intraoperative patient immobilization without the need for additional neuromuscular blocking drugs and reduces pain intensity and analgesic requirements for 48 h after spine surgery, which is not achieved with only opioid-based protocol.