Magnesium status and magnesium therapy in cardiac surgery: A systematic review and meta-analysis focusing on arrhythmia prevention.

PURPOSE To investigate magnesium as prophylaxis or treatment of postoperative arrhythmias in cardiac surgery (CS) patients. To assess impact on biochemical and patient-centered outcomes. MATERIALS AND METHODS We searched MEDLINE, CENTRAL and EMBASE electronic databases from 1975 to October 2015 using terms related to magnesium and CS. English-Language RCTs were included involving adults undergoing CS with parenterally administered magnesium to treat or prevent arrhythmias, compared to control or standard antiarrythmics. We extracted incidence of postoperative arrhythmias, termination following magnesium administration and secondary outcomes (including mortality, length of stay, hemodynamic parameters, biochemistry). RESULTS Thirty-five studies were included, with significant methodological heterogeneity. Atrial fibrillation (AF) was most commonly reported, followed by ventricular, supraventricular and overall arrhythmia frequency. Magnesium appeared to reduce AF (RR 0.69, 95% confidence interval (95%CI) 0.56-0.86, p=0.002), particularly postoperatively (RR 0.51, 95%CI 0.34-0.77, p=0.003) for longer than 24h. Maximal benefit was seen with bolus doses up to 60mmol. Magnesium appeared to reduce ventricular arrhythmias (RR=0.46, 95%CI 0.24-0.89, p=0.004), with a trend to reduced overall arrhythmias (RR=0.80, 95%CI 0.57-1.12, p=0.191). We found no mortality effect or significant increase in adverse events. CONCLUSIONS Magnesium administration post-CS appears to reduce AF without significant adverse events. There is limited evidence to support magnesium administration for prevention of other arrhythmias.