Magnesium sulphate(MgSO4), NMDA receptor antagonist is used as an adjuvant to analgesics and anaesthetics for intraoperative and postoperative analgesia. It is known to reduce perioperative and postoperative requirement of analgesics. A prospective, randomized, double blind study is done to assess the effect of intravenous Magnesium sulphate on post operative analgesic requirement following spinal anaesthesia in infra umbilical surgeries.

Fifty patients( ASA I and II) were selected randomly and divided into 2 groups. After spinal anaesthesia with 2.5 ml of Bupivacaine 0.5% (Hyperbaric), Group M received intravenous MgSO4 50 mg/kg through continuous infusion for 15 min and then 15 mg/kg/hr until the end of surgery. Group S received same volume of Isotonic saline over same period. Postoperatively, pain intensity is assessed using VAS score. Duration of postoperative analgesia is noted from the time of spinal anaesthesia to first demand of rescue analgesics. Pain score noted immediate, 30 min, 1 hr, 2 hr, 6 hr, 12 hr and 24 hr postoperatively.

Postoperative scores were significantly lower in Group M at 4 hr, 12 hr and 24 hr after surgery compared to that of Group S. Consumption of rescue analgesics at 12 and 24 hr after surgery was also significantly decreased in Group M.

Use of Intravenous Magnesium sulphate improves postoperative analgesia and reduces analgesic requirement without having effect on onset and recovery from spinal anaesthesia