Intravenous magnesium sulfate for analgesia in spinal surgery: a systematic review and meta-analysis of randomized controlled trials.

STUDY OBJECTIVE: To evaluate the effects of perioperative intravenous magnesium sulfate on postoperative pain, opioid consumption, recovery, and adverse events in patients undergoing spinal surgery. DESIGN: Systematic review with meta-analysis. SETTING: Perioperative setting. PATIENTS: Twenty-one randomized controlled trials including 1271 adult patients. INTERVENTIONS: Perioperative intravenous magnesium sulfate. MEASUREMENTS: Two researchers independently evaluated the risk of bias of included randomized controlled trials using the Cochrane Risk-of-Bias Tool 2.0 (RoB 2). Disagreements were settled by discussion or consultation with a third reviewer. We used funnel plots to detect publication bias when at least 10 studies were available, and adopted the leave-one-out sensitivity analysis to verify the robustness of pooled results. The certainty of evidence for each outcome was rated via the GRADE framework from five dimensions, with evidence classified into four grades: high, moderate, low and very low. MAIN RESULTS: Perioperative intravenous administration of magnesium sulfate can reduce postoperative 24-h pain scores (MD: -0.55, 95% CI: -1.01 to - 0.10, P = 0.02) and opioid consumption (MD: -4.95 mg, 95% CI: -8.74 to - 1.15 mg, P = 0.01). Furthermore, effect was more pronounced in the subgroup receiving a loading dose plus a maintenance dose. Perioperative intravenous magnesium administration significantly reduced intraoperative opioid consumption. Compared to the control group, magnesium sulfate was associated with a lower incidence of postoperative nausea and vomiting, but a higher incidence of hypotension. Meanwhile, intraoperative intravenous administration of magnesium sulfate appears to prolong the time to follow commands and the time to recovery of orientation. CONCLUSIONS: Perioperative magnesium sulfate improves analgesia and reduces opioid consumption in spinal surgery, especially with a bolus-plus-infusion regimen. However, it may delay emergence and increase hypotension risk. Careful hemodynamic monitoring is recommended for high-risk patients.