Preoperative oral magnesium loading to prevent postoperative atrial fibrillation following coronary surgery: a prospective randomized controlled trial.

Objectives: Postoperative atrial fibrillation (POAF) is common following coronary artery bypass grafting (CABG) surgery. Hypomagnesemia is frequent after CABG surgery. No previous trials have assessed the effect of preoperative magnesium (Mg) loading on POAF incidence.

Methods: This was a single-centre, double-blind, placebo-controlled, parallel-group trial, with balanced randomization [1:1]. The participants were recruited from November 2018 until May 2019. Patients received either 3.2 g of Mg daily (4 tablets of 0.4 g each twice daily) for 72 h preoperatively and 1.6 g of Mg (4 tablets) on the day of surgery or placebo tablets.

Results: The primary outcome was the incidence of POAF. Secondary outcomes included time to extubation, transfusion rate, critical care unit and hospital length of stay. Of the 210 randomized participants, 200 (100 in each group) completed the study. A total of 10 (10%) and 22 (22%) subjects developed POAF in the Mg and placebo groups, respectively (RR = 0.45, 95% confidence interval: 0.23-0.91). Hospital and critical care unit length of stay were comparable between the 2 groups. No side effects related to Mg administration were documented.

Conclusions: In this randomized controlled trial, preoperative loading with oral administration of Mg for 3 days in patients admitted for CABG surgery decreases the incidence of POAF compared to placebo.

Clinical Trial Registration Number: NCT03703349.