Effect of intraoperative magnesium sulfate infusion on early postoperative opioid consumption in laparoscopic hysterectomy: a randomized, double-blind, controlled trial

Aim: To investigate whether intraoperative intravenous magnesium sulfate, added to a standard multimodal analgesia regimen, reduces cumulative opioid consumption during the first 24 hours after laparoscopic hysterectomy.Material and Methods: In this single-center, prospective, randomized, double-blind, placebo-controlled trial, 40 adults scheduled for laparoscopic hysterectomy were randomized (1:1) to receive magnesium sulfate (20 mg/kg IV loading dose followed by a continuous infusion of 20 mg/kg/h until the end of surgery) or an equal volume of 0.9% saline. Postoperative analgesia was standardized using a predefined multimodal regimen and fentanyl based patient controlled analgesia; tramadol was administered as rescue analgesia when the Numeric Rating Scale (NRS) pain score was ≥ 4. The primary outcome was total opioid consumption within the first 24 postoperative hours, expressed as morphine milligram equivalents (MME). Secondary outcomes included NRS pain scores at rest and with movement at prespecified time points, postoperative nausea and vomiting (PONV), Ramsay sedation scores, rescue analgesic requirement, and intraoperative hemodynamic variables.Results: Total fentanyl consumption (255 [182.5–392.5] μg vs 465.0 [262.5–500.0] μg; p=0.008) and total opioid consumption MME (34.5 [26.9–42.9] mg vs 50.0 [31.3–69.1] mg; p=0.011) were significantly lower in the magnesium group. NRS scores, PONV incidence, and Ramsay sedation scores did not differ at any time point. Mean arterial pressure was higher at minute 20 in the magnesium group (p=0.011), while hypotension and bradycardia rates were comparable.Conclusion: Intraoperative magnesium sulfate reduced 24 h postoperative opioid requirements without improving pain scores, supporting magnesium as an opioid-sparing adjunct within multimodal analgesia.