Campbell NG, Allen E, Montgomery H, et al. - In an effort to avert atrial fibrillation after cardiac surgery (AFACS), high levels of serum potassium levels are frequently maintained (≥ 4.5 mEq/L), for which there is limited evidence. Prior to performing a non-inferiority randomized controlled trial examining the non-inferiority of maintaining levels ≥ 3.6 mEq/L vs this strategy, researchers herein sought to determine the feasibility, acceptability and safety of recruiting for such a trial. Randomization (1:1) of 160 people undergoing first-time elective isolated coronary artery bypass grafting (CABG) was planned to protocols aiming to maintain serum potassium at either ≥ 3.6 mEq/L or ≥ 4.5 mEq/L after arrival on the postoperative care facility and for 120 hours or until discharge from hospital or AFACS occurred, whichever happened first. Outcomes that were primarily assessed included: (1) whether 160 patients could be recruited and randomized over 6 months (estimated 20% of those eligible), (2) maintaining supplementation protocol violation rate ≤ 10% (defined as potassium supplementation being inappropriately administered or withheld according to treatment allocation after a serum potassium measurement), and (3) retaining 28 day follow-up rates ≥ 90% after surgery. As per outcomes, no evidence suggested that this strategy is beneficial compared with maintaining potassium (≥ 3.6 mEq/L). This work supports the feasibility and safety of performing a non-inferiority RCT to ascertain the efficacy of this approach.