Impact of intravenous magnesium on post-cardiothoracic surgery atrial fibrillation and length of hospital stay: a meta-analysis.

Postoperative atrial fibrillation can occur in 25% to 40% of patients undergoing cardiothoracic surgery. Although the majority of postoperative atrial fibrillation is benign, it has been associated with prolonged hospital length of stay. Magnesium prophylaxis against postoperative atrial fibrillation has been evaluated in several clinical trials; however these trials were small in size and therefore conveyed mixed or inconclusive results. In an attempt to better understand magnesium's role in this setting, we conducted a meta-analysis. A systematic literature search was conducted from January 1999 through August 2004 to identify trials of prophylactic magnesium in the setting of cardiothoracic surgery. The primary outcome measure was the incidence of postoperative atrial fibrillation. Trials were further analyzed based on cumulative doses of magnesium and perioperative time of initiation of prophylaxis, as well as length of stay. Seven randomized trials were identified. Upon meta-analysis, magnesium was found to prevent postoperative atrial fibrillation with an odds ratio of 0.66 and 95% confidence interval of 0.51 to 0.87. The incidence of postoperative atrial fibrillation was also significantly reduced in the low dose with an odds ratio of 0.36 and 95% confidence interval of 0.23 to 0.56, and in the preoperative groups with an odds ratio of 0.46 and 95% confidence interval of 0.31 to 0.67. Prophylactic magnesium reduced length of stay (n = 6 studies) by a weighted mean difference of 0.29 days, with a 95% confidence interval 0.54 to 0.05. Prophylactic magnesium reduced cardiothoracic surgery patients' risk of postoperative atrial fibrillation and length of stay. Administering lower doses and initiating prophylaxis in the preoperative period achieved the greatest reduction in postoperative atrial fibrillation.