Effects of Intravenous Magnesium-Sulphate on Postoperative Analgesia following Myomectomies and Hysterectomies

Background: Opioids are the mainstay of postoperative analgesic, but with many side effects. We explored the analgesic effects of magnesium preloading in abdominal surgeries. Methodology: Eighty patients, 18 – 65 years, ASA I-III, were randomised into groups M and N. Prior to induction of general anaesthesia, group M received IV magnesium 50mg/kg preloading while group N received placebo, both in 100mls 0.9% saline over 15 mins. All patients had paracetamol 1gm, pethidine 0.5mg/kg and wound infiltration. The time to first request for rescue IV pentazocine, total rescue opioid use, postoperative VAS pain scores over 24-hours, side effects profile and satisfaction score were compared. Results: Demographic parameters were comparable, p-value ˃ 0.05. The mean time to first request for rescue analgesia was prolonged in group M (219.25 ± 148.88 mins) compared to group N (82.25 ± 46.51 mins). The mean postoperative VAS pain scores were lower in group M versus group N over 24-hours (p ˂ 0.05). The mean 24-hours rescue opioid use was lower in group M (49.23 ± 20.05mg) versus group N (87.00 ± 15.27mg), p-value 0.001. PONV was lower in group M versus N, p-value 0.001. Group M had better satisfaction score versus N, p-value 0.001. Conclusion: Magnesium 50mg/kg preloading provided effective postoperative analgesia, and lower rescue opioid use and PONV incidence following gynaecological surgeries.