Effects of Intravenous Magnesium Sulphate Administration on Postoperative Analgesia in Infraumbilical Surgeries under Spinal Anaesthesia: A Double Blinded Randomised Clinical Study

Introduction: Inadequate management of postoperative pain can lead to complications like prolonged recovery time, ileus, nausea, urinary retention, and infection. Although spinal anaesthesia is highly effective in intraoperative pain relief, its effects wear off after surgery, with a tendency to produce opioid dependence. Magnesium sulphate, an NMDA receptor blocker, has the potential to augment spinal anaesthesia effects and postoperative analgesia. Aim: To determine whether intravenous magnesium sulphate infusion could improve postoperative pain management in patients who had undergone spinal anaesthesia for infraumbilical surgery. Materials and Methods: The present double-blind, randomised clinical trial including 60 American Society of Anaesthesiologists (ASA) I-II patients who had infraumbilical spinal anaesthesia was conducted at Dr. D. Y. Patil Medical College in Pune, Maharashtra, India. Patients were given 15 mg of 0.5% hyperbaric bupivacaine intrathecally, along with a random assignment to receive either intravenous magnesium sulphate (Group M) or normal saline (Group C). Statistical Package for Social Sciences (SPSS) v27 was used to assess and analyse postoperative pain {Visual Analogue Scale (VAS)}, haemodynamics, block characteristics, time to first analgesia, and side-effects. The data was collected, compiled and tabulated. Data entry was done in Microsoft Excel and tables and apt charts was formed. Quantitative data was analysed using unpaired student t-test and qualitative data was analysed using Chi-square test analysed by SPSS software 27. Results: Demographic characteristics and haemodynamic data were similar across groups. The mean age of the patients was 41.93±11.64 in Group M and 36±13.5 in Group C. VAS scores in Group M were lower from 45 minutes through to 16 hours postoperative compared with Group C. Analgesic duration was longer, and the time to the first rescue analgesia in Group M was longer than in Group C. The time to onset for sensory and motor block was identical, but blocks lasted significantly longer in Group M. Conclusion: Intravenous magnesium sulphate as an adjuvant to spinal anaesthesia safely extends postoperative analgesia, decreases pain severity, and postpones the need for rescue analgesia without inducing significant haemodynamic instability or side-effects. Therefore, magnesium sulphate is an effective and safe adjuvant for enhancing postoperative pain relief in infraumbilical operations.