title: Prophylactic magnesium does not prevent atrial fibrillation after cardiac surgery: a meta-analysis.
abstract: BACKGROUND
  Atrial fibrillation (AF) is a common complication after cardiac surgery. Previous meta-analyses have concluded prophylactic magnesium (Mg) prevents postoperative AF, although with a significant degree of heterogeneity among included studies. Recently, the largest randomized, controlled trial published to date (but not included in prior published meta-analyses) concluded that Mg sulfate is not protective against AF after cardiac surgery. The objective of this study was to conduct a new meta-analysis including the results of new Mg trials not included in previous meta-analyses, and to investigate the potential causes and effects of significant heterogeneity observed in previously published meta-analyses.
  
  
  METHODS
  The MEDLINE, EMBASE, and CENTRAL databases were searched for relevant studies published up to March 31, 2012. Pooled odds ratios of occurrence of AF were calculated using random-effects models. Heterogeneity was assessed as significant using the I(2) statistic.
  
  
  RESULTS
  Egger's and funnel plots demonstrated biases toward stronger and more positive effects of Mg in smaller studies. When the analysis was restricted to the five double-blind, intention-to-treat studies in which AF was the primary outcome (Mg arm, n = 710; control arm, n = 713), Mg did not prevent postoperative AF (odds ratio, 0.94; p = 0.77), and heterogeneity was no longer significant (I(2) = 40%; p = 0.15).
  
  
  CONCLUSIONS
  This meta-analysis, restricted to well-conducted trials, does not support the prophylactic use of Mg to prevent AF after cardiac surgery. Prior meta-analyses have drawn conclusions from simple random-effects models with significant heterogeneity. However, this approach leaves important residual heterogeneity and overemphasizes the strongly positive effects of smaller studies.
authors.affiliation: Division of Cardiovascular Surgery, University of British Columbia, Vancouver, British Columbia, Canada. richard.cook@vch.ca
authors.forename: Richard C
authors.initials: RC
authors.lastname: Cook
authors.forename: Michael H
authors.initials: MH
authors.lastname: Yamashita
authors.forename: Mark
authors.initials: M
authors.lastname: Kearns
authors.forename: Krishnan
authors.initials: K
authors.lastname: Ramanathan
authors.forename: Ken
authors.initials: K
authors.lastname: Gin
authors.forename: Karin H
authors.initials: KH
authors.lastname: Humphries
mesh_terms: D001281:Atrial Fibrillation / Q000209:etiology* / Q000517:prevention & control*; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D006801:Humans; D008274:Magnesium / Q000627:therapeutic use*; D017211:Treatment Failure
chemical_list: D008274:Magnesium