Effect of Two Doses of Magnesium Sulphate on Post-Operative Analgesia Following Emergency Exploratory Laparotomy Under General Anesthesia

Opioids are frequently employed in postoperative analgesia, but their use is associated with numerous side effects, which have led to the search for non-opioid adjuncts. This study compared the effect of two doses of magnesium sulphate on post-operative analgesia following emergency exploratory laparotomy. This was a double blind randomized comparative study of ninety adult surgical patients scheduled for emergency exploratory laparotomy. Patients were randomly assigned to three groups to receive normal saline (group N), IV Magnesium sulphate 40 mg/kg over 15 mins (group MB), or IV Magnesium sulphate 40 mg/kg over 15 mins followed by an infusion of 10 mg /kg/hr till the end of surgery (group MI). The postoperative numeric rating scale for pain, time to first request for analgesia, morphine consumption, and patients’ satisfaction with analgesia were measured. Age, weight, and pain scores were presented as means and standard deviations and analyzed using the Student t-test for comparisons between 2 groups and ANOVA for comparisons within 3 groups. The level of statistical significance was set at p <0.05. There was a significant reduction (26%) in 24-hour morphine consumption (p< 0.001) and prolongation of time to first analgesic request (p<0.001) in the magnesium-treated groups compared with the control. However, there was no significant difference in the numeric rating scale for pain (p>0.99) and patients’ satisfaction with post-operative analgesia (p=0.258) in the three groups. This study demonstrated that the administration of magnesium sulphate reduced 24-hour morphine consumption and prolonged the time to first request for analgesia.