The effect of magnesium sulfate on postoperative analgesia requirements in gynecologic surgeries

Background: Recent studies have shown the positive effect of Magnesium Sulphate (MgSO4) on pain reduction and postoperative analgesics requirement in patients undergoing surgery. We assessed the effect of MgSO4 on intra-operative and postoperative analgesic requirements in patients undergoing lower abdominal gynecologic laparotomy.
Materials and Methods: This randomized clinical trial was conducted on 30 female patients at Rasool-e-Akram (referral and academic) hospital in Tehran from August 2012 till March 2013. These patients who were candidate for gynecologic surgeries (hysterectomy and/or myomectomy) were randomized into study (n=15) and control (n=15) groups. Same anesthetic technique was used in all patients. Besides induction of the anesthesia in the study group, for analgesic purposes we administered MgSO4 50 mg/ kg/hr. intravenously (IV) as a bolus dose and then 8 mg/kg IV as maintenance dose. Control group received the same anesthetic agents and the same amount of isotonic saline instead of MgSO4. Analgesic consumption was measured in both groups postoperatively within 24 hours. Visual Analog scale (VAS) was used for postoperative pain evaluation in both groups.
Results: There was a decrease in analgesic consumption and pain in the group receiving MgSO4, in comparison to control group. Pain severity assessment, 24 hours post operatively showed similar results in both groups. There was a statistically significant difference regarding prescribed dose of Pethidine in study and control groups (p=<0.0001).
Conclusion: Intra-operative MgSO4 is effective in postoperative pain control following lower abdominal laparotomy. Further studies with larger sample sizes and longer follow up should be performed to obtain more informations about safety and to determine whether doses of magnesium sulfate can provide postoperative analgesic benefits