Postoperative magnesium sulfate and atrial fibrillation after coronary artery bypass grafting: a single-center retrospective comparative cohort study

Postoperative atrial fibrillation (POAF) is a common complication following coronary artery bypass grafting (CABG). Magnesium sulfate has been evaluated as a preventive strategy. This study investigated whether early postoperative magnesium supplementation is associated with reduced new-onset POAF, shorter hospital length of stay (LOS), lower incidence of premature ventricular contractions (PVCs), and less postoperative surgical bleeding after on-pump CABG. We conducted a quantitative, retrospective, single-center, comparative cohort study at the Specialized Arab Hospital (Nablus, Palestine). Consecutively sampled adults undergoing first-time elective on-pump CABG between January 2021 and December 2023 were included (N = 220). Per an institutional, serum-triggered (threshold-based) protocol, 108 patients received intravenous magnesium sulfate (MgSO₄) within the first 48 postoperative hours; 112 did not. Exploratory adjusted analyses were also performed for POAF and LOS using available demographic and operative covariates. The incidence of POAF was significantly lower in the MgSO₄ group (11.1%) than in the No MgSO₄ group (78.6%) (p < 0.0001). MgSO₄ was also associated with a shorter LOS (5.26 ± 0.44 vs. 5.51 ± 0.71 days; p = 0.002). Postoperative surgical bleeding was lower with borderline significance in the MgSO₄ group (2.73% vs. 9.55%; p = 0.050). The incidence of PVCs was lower with MgSO₄ (5.91% vs. 20.0%; p = 0.002). In exploratory adjusted analyses, MgSO₄ exposure remained independently associated with lower odds of POAF and shorter LOS. Threshold-based postoperative magnesium sulfate administered within the first 48 h after on-pump CABG surgery was associated with a reduced incidence of POAF, a shorter LOS, and fewer PVCs; the reduction in surgical bleeding was borderline. Exploratory adjusted analyses for POAF and LOS supported the robustness of these associations. These observational findings support prospective—ideally randomized—evaluation to confirm effectiveness and define optimal dosing and serum targets.