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AMBULATORY ANESTHESIA

An Evaluation of a Single Dose of Magnesium to Supplement Analgesia After Ambulatory Surgery: Randomized Controlled Trial

Martin R. Tramèr, MD, DPhil^*, and Chris J. Glynn, FRCA, MSc

From the *Division of Anesthesiology, Department Anesthesiology, Pharmacology and Intensive Care, Geneva University Hospitals, Geneva, Switzerland; and Pain Relief Unit, Nuffield Department of Anesthetics, The Churchill, Oxford, UK.

Address correspondence and reprints requests to Prof. Tramèr, Division of Anesthesiology, University Hospitals of Geneva, CH-1211 Geneva 14, Switzerland. Address e-mail to martin.tramer{at}hcuge.ch.

BACKGROUND: Previous studies have suggested that magnesium may be a useful adjuvant to postoperative analgesia.

METHODS: We randomized adults undergoing ambulatory ilioinguinal hernia repair or varicose vein operation under general anesthesia (propofol, fentanyl, isoflurane-N₂O) to receive magnesium sulfate 4 g IV or physiological saline after induction. All patients preoperatively received diclofenac 100 mg rectally and those undergoing hernia repair had a postoperative ilioinguinal-iliohypogastric nerve block done. Pain, analgesic consumption, and adverse effects were recorded in the recovery room and, using a questionnaire, up to 3 days postoperatively.

RESULTS: We randomized 200 patients (101 magnesium, 99 placebo). There were no differences in hemodynamic variables before and immediately after study drug injection. Pain intensity at rest and on movement after 1, 2, and 4 h, time to first rescue analgesic, and cumulative numbers of non-opioid and opioid analgesics were similar among groups. There was no difference in the incidence of postoperative nausea and vomiting, dizziness, headache, or fainting. The incidence of postoperative shivering was significantly lower in the magnesium group (4% vs 13.1%, P = 0.0232). Adequately completed questionnaires were returned by 84 placebo and 82 magnesium patients. There was no difference between groups for any of the analyzed outcomes during the first three postoperative days, neither for patients undergoing inguinal hernia repair nor for those undergoing varicose vein stripping.

CONCLUSIONS: In patients undergoing ambulatory ilioinguinal hernia repair or varicose vein operations under general anesthesia supplemented with other analgesic adjuvants, pretreatment with IV magnesium sulfate 4 g has no impact on postoperative pain and analgesic consumption.

This article has been cited by other articles:

				C. Lysakowski, L. Dumont, C. Czarnetzki, and M. R. Tramer Magnesium as an Adjuvant to Postoperative Analgesia: A Systematic Review of Randomized Trials Anesth. Analg., June 1, 2007; 104(6): 1532 - 1539. [Abstract] [Full Text] [PDF]