Does the prophylactic administration of magnesium sulphate to patients undergoing thoracotomy prevent postoperative supraventricular arrhythmias? A randomized controlled trial.

BACKGROUND Supraventricular arrhythmias (SVA) are common after thoracic surgery and are associated with increased morbidity and mortality. This prospective, randomized, double-blind, placebo-controlled trial examined the effects of perioperative magnesium on the development of postoperative SVA. METHODS Two hundred patients undergoing thoracotomy for lobectomy, bi-lobectomy, pneumonectomy, or oesophagectomy were recruited and randomly allocated into two groups. The treatment group received magnesium (5 g daily) intraoperatively, and on days 1 and 2 after operation, the control group received placebo. The primary outcome of the study was the development of SVA within the first 5 days after operation. RESULTS There were 100 patients in each arm of the study, with one withdrawal and three lost to follow-up in the treatment group and four withdrawals in the control group. Ninety-six patients received magnesium and 96 received placebo. There was no difference in the incidence of SVA between the treatment and control groups, 16.7% (16/96) vs 25% (24/96), P=0.16. In the predefined subgroup analysis, patients at highest risk of arrhythmias (those undergoing pneumonectomy) had a significant reduction in the frequency of SVA, 11.1% (2/18) vs 52.9% (9/17), P=0.008. There were no differences in hospital length of stay or mortality. Patients receiving i.v. magnesium experienced a higher frequency of minor side-effects (stinging at injection site). The treatment was otherwise well tolerated. CONCLUSIONS Overall, prophylactic magnesium did not reduce the incidence of SVA in patients undergoing thoracotomy. However, it reduced the incidence of SVA in the high-risk cohort of patients undergoing pneumonectomy. (ISRCTN22028180.).