The effect of magnesium sulphate on postoperative analgesia requirements in gynecological surgeries

OBJECTIVE Recent studies have shown the positive effect of magnesium sulphate (MgSO4) on pain reduction and postoperative analgesic requirements in patients undergoing surgery. We assessed the effect of MgSO4 on intra-operative and postoperative analgesic requirements in patients undergoing lower abdominal gynecological 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 to March 2013. The patients who were candidates 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, we administered MgSO4 50 mg/kg/hr intravenously (IV) for analgesic purposes 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. The visual analog scale (VAS) was used for the evaluation of postoperative pain 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 in prescribed dose of pethidine between 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 information about safety and to determine whether doses of MgSO4 can provide postoperative analgesic benefits.