Evaluation of a single-dose of intravenous magnesium sulphate for prevention of postoperative pain after inguinal surgery

This study was undertaken to study efficacy of single dose of intravenous magnesium sulphate to reduce post-operative pain in patients undergoing inguinal surgery. One hundred patients undergoing inguinal surgery were divided randomly in two groups of 50 each. The patients of magnesium sulphate group (Group-I) received magnesium sulphate 50 mg/kg in 250 ml of isotonic sodium chloride solution IV whereas patients in control group (Group-II) received same volume of isotonic sodium chloride over 30 minutes preoperatively. Anaesthesia was induced with propofol (2 mg/kg) and pethidine (1 mg/kg). Atracurium besylate (0.5 mg/kg) was given to facilitate insertion of LMA. Pain at emergence from anaesthesia and 2, 4, 6, 12 and 24 hours after surgery was evaluated. The timing and dosage of rescue analgesic during first 24 hrs after operation was noted. Pain in postop period was significantly lower in magnesium sulphate group in comparison to control group at emergence from anaesthesia and 2, 4, 6, 12 and 24 hrs postop [1.86 vs. 1.96 (P=0.138), 1.22 vs. 1.82 (P=0.001), 1.32 vs. 1.88 (P=0.000), 2.74 vs. 3.84 (P=0.000), 1.36 vs. 2.00 (P=0.000) and 0.78 vs 1.30 (P=0.000), respectively]. Patients in group-I were more sedated as compared to group-II [sedation score 1.86 vs. 1.40 (P=0.000)]. Rescue analgesia requirement postoperatively in first 4, 8 and 16 hrs was significantly lower in patients of group-1 than in group- II [1.9 vs. 3.8 (P<0.05), 25.50 vs. 52.50 (P<0.05) and 0.000 vs. 7.5 (P<0.05)]. Preoperative magnesium sulphate infusion decreases postop pain and requirement of rescue analgesia.