Potassium and Magnesium Supplementation Do Not Protect Against Atrial Fibrillation After Cardiac Operation: A Time-Matched Analysis.

Retrospective observational study of 2,041 adults undergoing CABG, valve operation, or CABG+valve between 2009 and 2013; preoperative AF or atrial flutter excluded; time-matched analysis of electrolyte levels; multivariate logistic regression to identify predictors of POAF.

Intraoperative potassium supplementation: mean dose 26 ± 14 mEq; intraoperative magnesium supplementation: mean dose 2.5 ± 1.2 g; postoperative supplementation of potassium and magnesium during hospital admission per provider-dependent practices; ICU used a standardized repletion protocol for potassium when levels were below 4.0 mEq/L; magnesium repletion protocol not standardized; duration not specified.

POAF occurred in 752 of 2,041 patients (36.8%). Time-matched analysis showed higher potassium and magnesium levels near AF onset than in controls (p<0.001 for both). Potassium supplementation did not reduce POAF; magnesium supplementation was associated with higher POAF risk. Magnesium level was a strong independent predictor of POAF (OR 4.26; 95% CI 2.69–6.72; p<0.001); potassium level also independently predicted POAF (OR 1.57; 95% CI 1.25–1.97; p<0.001). Final model included age, Caucasian race, preoperative β-blocker use, valve operation, and postoperative pneumonia. Higher electrolyte quintiles correlated with higher POAF incidence. Authors conclude that maintaining near-normal electrolyte levels with current repletion practices does not reduce POAF and may be linked to higher risk; a randomized trial of standardized electrolyte repletion is needed.

Retrospective design with potential provider bias in electrolyte management; time-matched analysis limited to patients with complete data; only 899 patients had qualifying data for all three labs in multivariate analysis; results may not generalize to the full cohort; potential unmeasured confounding due to not including all postoperative medications.