Potassium and Magnesium Supplementation do not protect against Atrial Fibrillation after Cardiac Operation: a Time-Matched Analysis.

In this single institution retrospective study of postoperative cardiac surgery patients, serum potassium and magnesium levels at times when postoperative atrial fibrillation (POAF) occured were compared with levels in patients who did not experience POAF.  The incidence of POAF was 37%, and was associated with increasing magnesium levels.  Prophylactic potassium administration had no effect on POAF, whereas prophylactic magnesium administration was associated with an increase in POAF risk.