Comparison of perioperative magnesium sulphate infusion with placebo for postoperative analgesia.

Abstract

Adequate control of post-operative pain is very essential to reduce discomfort and early recovery after surgery. Role of adjuvant drugs along with conventional analgesic drugs have gained popularity in recent years, out of which MgSO₄ is one of them. Objectives: To compare mean duration of postoperative analgesia between perioperative infusion of magnesium sulfate versus placebo in patients undergoing upper abdominal surgery. Study Design: Randomized Controlled Trial. Setting: Nishtar Medical University/Hospital Multan. Period: March-2018 to Dec-2018. Material and Methods: A total number of 100 patients admitted for upper abdominal surgery in the Department of Surgery, Nishtar Hospital Multan were included in this analysis. Group A received 50 mg/kg i/v of MgSO₄ in 0.9% N/S at induction and 15 mg/kg MgS0₄ per hour, 6 hours postoperatively. While group B received 100 ml of 0.9% N/S at induction and 500 ml of 0.9% N/S 6 hours postoperatively. Post-op pain score was noted at 01 and 06 hours after surgery. Time for requirement of first rescue analgesia was also noted. Results: Mean post-op pain (VAS score) after 01 hour of surgery was 2.7+0.43 in MgSO₄ group versus 4.1+0.82 in control group (p-value <0.001). VAS score after 06 hours was 1.9+0.31 in MgSO₄ group versus 2.3+0.63 in control (p-value <0.001). Time of first rescue analgesia was prolonged in MgSO₄ group; 105.9+12.7 minutes versus 67.8+15.3 minutes in control group with p-value <0.001. Conclusion: Magnesium sulfate increases the duration of postoperative analgesia and can be used as an adjunct since this molecule is inexpensive, relatively harmless, and the biological basis for its potential anti-nociceptive effect is promising.