Effect of Intraoperative Magnesium Infusion on Perioperative Analgesia in Open Cholecystectomy

Study Objective: To study the role of magnesium sulphate (MgSO4) on analgesic requirement, pain, discomfort, and sleep during perioperative period.

Design: prospective, double-blinded, randomized study.

Settings: Operating room and recovery ward at a university teaching hospital.

Patients: 50 ASA physical status I and II patients scheduled for elective open cholecystectomy with general anesthesia.

Interventions: patients were randomly allocated to receive MgSO4 or saline intravenously (i.v.). Patients in the magnesium group received 50% MgSO4 (50 mg kg(-1)) in 100 mL saline and those in the control group received an equal volume of saline i.v. during the preoperative period followed by 50 mL hr(-1) infusion of either MgSO4 (15 mg kg(-1) hr(-1)) or saline until the end of surgery.

Measurements And Main Results: Morphine requirement, pain during rest and on coughing, discomfort, and insomnia were assessed during the postoperative period for 24 hours. Intravenous morphine 40 microg kg(-1) increments were given to all patients in the postoperative period for analgesia. Patients in the magnesium and control groups had similar morphine requirement during the first 24 hours postoperatively (p = 0.07). Patients in the magnesium group experienced less discomfort during the first hour after the operation. They also had better sleep quality during the first postoperative night than did the control group patients (p < 0.05). The frequency of side effects was similar in the two groups.

Conclusion: Administration of intraoperative MgSO4 as an adjuvant analgesic in patients undergoing open cholecystectomy resulted in better pain relief and comfort in the first postoperative hour, but it did not significantly decrease the postoperative morphine requirement. Magnesium sulphate resulted in better sleep quality during the postoperative period, without any significant adverse effects. The role of MgSO4 as an adjuvant analgesic in open cholecystectomy needs to be studied further.