Evaluation Of Intravenous Magnesium Sulphate For Postoperative Analgesia In Upper Limb Orthopaedic Surgery Under General Anaesthesia: A Comparative Study

BackgroundThis randomised, placebo-controlled, double-blind study designed to assess the efficacy of intravenous magnesium sulphate to reduce postoperative pain in upper limb orthopaedic surgery (duration of surgery≤120minutes) under general anaesthesia using thiopentone, fentanyl, vecuronium,N2O/O2 and isoflurane.MethodAfter obtaining written informed consent from 100 ASA I-II patients, they were divided randomly into two groups of 50 each. Group M received magnesium sulphate 30 mg/kg as a bolus before induction and 10 mg/kg/hour by infusion. Group S patients received same volume of normal saline. All the vital parameters were recorded at the time of start of administering drugs and at 10 minutes interval till the end of study. All patients received injection meperidine 0.5-1mg/kg intramuscular (IM) and diclofenac 75 mg IM as soon as they complained of pain or when the visual analogue scale (VAS) became >3cm. Pain by using VAS, during first hour and 3, 6, 12, 18 and 24 hours after surgery was noted. The timing and dosage of rescue analgesic during first 24hrs after operation was noted.ResultPain in the postoperative period was significantly lower in group M compared to in group S during first hour and 3,6,12 and 18 hrs postoperatively. Patients in group M were more sedated as compared to group S [sedation score 1.32 vs. 1.88 (p=0.000)]. Rescue analgesia requirement postoperatively was significantly lower in patients of group M than group S.ConclusionIntravenous Magnesium sulphate decreases postoperative pain and cumulative analgesic requirement without any clinically significant adverse reaction.