Intravenous magnesium sulfate for post-operative pain in patients undergoing lower limb orthopedic surgery.

Introduction: This study looks at the effect of supplementary intravenous magnesium sulfate on acute pain when administered in patients undergoing lower limb orthopedic surgery using spinal anesthesia with bupivacaine. Method and materials: In this double-blind, randomized, placebo-controlled clinical trial, 60 patients were selected and randomly divided into two groups. Efforts were made to place both groups under the same method of anesthesia. One group received 8 mg/kg intravenous magnesium sulfate, started before the incision and continued up to the end of the surgical procedure, using a 50 ml syringe, via a peripheral large bore catheter; the second group received the same volume of placebos using the same method. To present the results, mean (± SD) was used; a P value of <0.05 was considered significant. Results: There was no difference between the two groups in terms of the basic variables. Pain reported by the first group that received magnesium sulfate was significantly less at the first, third, sixth and 12th hours after the operation in comparison with the group that received placebo. Also, the intravenous morphine requirements in the first 24 h after the surgery were less in the magnesium group (4.2 ± 1.6 mg) than in the control group (9.8 ± 2.1 mg). Conclusion: Intravenous magnesium sulfate can serve as a supplementary analgesic therapy to suppress the acute post-operative pain, leading to less morphine requirements in the first 24 h.