Effect of intravenous infusion of magnesium sulphate on postoperative analgesia in patients undergoing arthroscopic knee surgeries under spinal anaesthesia

Revi N, Mithun Raju P, Mohsin Mohammed Ali


Background: Magnesium sulphate is being used for postoperative pain relief intravenously, intrathecally and epidurally. Currently, it is also gaining popularity as an adjuvant in blocks. The objective of the study was aimed at the postoperative analgesic effects of magnesium sulphate when given as intravenous infusion in patients undergoing arthroscopic knee surgeries under spinal anaesthesia and to compare the postoperative analgesic effects of magnesium sulphate infusion in a study cohort who received magnesium sulphate with the control cohort who were not given magnesium sulphate and underwent arthroscopic knee surgeries under spinal anaesthesia.

Methods: After obtaining ethical committee clearance and consent from the patients, 31 patients each were placed in study cohort and control cohort. Spinal anaesthesia was administered in the lateral decubitus position through the L3–4 or L4–5 interspace. Hyperbaric bupivacaine 0.5% solution with fentanyl 20 μg was injected intrathecally. After spinal anaesthesia, patients received magnesium sulphate 50 mg/kg for 15 min and then 15 mg/kg/hr by continuous intravenous infusion until the end of surgery. The other group did not receive magnesium sulphate infusion. Postoperative pain scores and postoperative analgesic consumption were the primary end points.

Results: The results of the study reveal the efficacy of perioperative intravenous infusion of magnesium sulphate in prolonging the spinal block as well as reducing the postoperative pain scores without hemodynamic variability or side effects.

Conclusions: Post-operative pain and analgesic consumption was reduced with the use of intravenous magnesium following spinal anaesthesia.


Cohort study, Intravenous infusion, Intravenous infusion, Magnesium sulphate

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