Meta-analysis of randomized controlled trials on magnesium in addition to beta-blocker for prevention of postoperative atrial arrhythmias after coronary artery bypass grafting

BMC Cardiovascular Disorders (Impact Factor: 1.88). 01/2013; 13(1):5. DOI: 10.1186/1471-2261-13-5
Source: PubMed


Atrial arrhythmia (AA) is the most common complication after coronary artery bypass grafting (CABG). Only beta-blockers and amiodarone have been convincingly shown to decrease its incidence. The effectiveness of magnesium on this complication is still controversial. This meta-analysis was performed to evaluate the effect of magnesium as a sole or adjuvant agent in addition to beta-blocker on suppressing postoperative AA after CABG.

We searched the PubMed, Medline, ISI Web of Knowledge, Cochrane library databases and online clinical trial database up to May 2012. We used random effects model when there was significant heterogeneity between trials and fixed effects model when heterogeneity was negligible.

Five randomized controlled trials were identified, enrolling a total of 1251 patients. The combination of magnesium and beta-blocker did not significantly decrease the incidence of postoperative AA after CABG versus beta-blocker alone (odds ratio (OR) 1.12, 95% confidence interval (CI) 0.86-1.47, P = 0.40). Magnesium in addition to beta-blocker did not significantly affect LOS (weighted mean difference −0.14 days of stay, 95% CI −0.58 to 0.29, P = 0.24) or the overall mortality (OR 0.59, 95% CI 0.08-4.56, P = 0.62). However the risk of postoperative adverse events was higher in the combination of magnesium and beta-blocker group than beta-blocker alone (OR 2.80, 95% CI 1.66-4.71, P = 0.0001).

This meta-analysis offers the more definitive evidence against the prophylactic administration of intravenous magnesium for prevention of AA after CABG when beta-blockers are routinely administered, and shows an association with more adverse events in those people who received magnesium.

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    ABSTRACT: Magnesium (Mg) is an important intracellular ion with electrophysiological properties. It is essential for optimal metabolic cell function. Serum Mg is a poor predictor of body stores, as less than 1 % of total body Mg is found in serum. Ionized Mg assessment, the active portion of Mg, may be a more useful indicator than total serum Mg assessment. Hypomagnesemia is common in the cardiac surgical population and correlates with higher incidence of cardiac arrhythmias and major adverse cardiac events. However, the role of Mg in preventing postoperative arrhythmias – especially atrial fibrillation – is controversial. There is moderate evidence that intravenous Mg therapy, particularly low doses administered before cardiac surgery, will reduce the postoperative incidence of atrial fibrillation. Hypomagnesemia is also common in hospitalized patients. It is especially prevalent in the critically ill and correlates with worse clinical outcomes. Mg has proven effective for treating eclampsia, preeclampsia, and torsades de pointes. Other therapeutic applications such as adjunctive therapy in acute asthma exacerbations, acute coronary syndromes, acute cerebral ischemia, and postoperative pain control are under discussion. Mg has a low adverse effects profile and multiple theoretical advantages, including its low cost.
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