Abstract 4776: Prophylactic Intravenous Magnesium Sulphate in Addition to Oral Beta Blockade does not Prevent Atrial Arrhythmias after Cardiac Surgery

Abstract

Background Atrial arrhythmias (AA) affect up to 40% of patients following cardiac surgery. The best strategy for prevention of AA remains undetermined, however, beta blocker (BB) administration is the standard of care at many centers (including ours). Although there is now compelling evidence demonstrating the utility of magnesium sulphate (MgSO4) for treatment of AA, the effectiveness of MgSO4 for prophylaxis of AA remains controversial. This study is the largest randomized, placebo-controlled trial of intravenous (IV) MgSO4 for the prevention of AA following cardiac surgery. Methods Eligible patients requiring either coronary artery bypass graft surgery (CABG), or valve surgery ± CABG, were randomized to receive either 5g IV MgSO4, or placebo upon removal of the crossclamp, followed by daily infusions of IV MgSO4 or placebo over 4 hours, from the day of surgery until post-operative day 4. All patients were treated according to an established protocol with oral BB (atenolol). Patients were monitored by continuous telemetry for the first 5 post-operative days. The primary endpoint was an AA lasting ≥ 30 minutes, or requiring treatment because of hemodynamic compromise. Results Table 1 summarizes the results. There was no difference in the incidence of AA between patients who received IV MgSO4 or those who received placebo. Conclusions In patients proactively treated with atenolol using an established protocol, the addition of daily IV MgSO4 infusions for 5 days post-operatively did not reduce the incidence of clinically important AA following cardiac surgery. Results For Primary Outcome (Post-Operative AA)