LONDON —
“The widespread practice of giving patients potassium after bypass heart surgery even though their blood levels are within the normal range can be abandoned,” said Benjamin O’Brien, MD, PhD, director of the Clinic for Cardioanesthesiology and Intensive Care Medicine at Charité Hospital in Berlin, Germany.
Results from the randomized TIGHT-K trial that assessed two levels of potassium supplementation were presented at the annual congress of the European Society of Cardiology.
In the tight-control group, supplementation was provided to maintain high-normal levels of potassium (> 4.5 mEq/L). In the relaxed-control group, supplementation was provided only when potassium levels fell below the low-normal threshold (< 3.6 mEq/L).
Trial Upending Popular Practice
The multinational trial involved 23 centers in Germany and the United Kingdom. All 1690 participants enrolled were scheduled to undergo a coronary artery bypass graft procedure, but Dr. O’Brien said he considers the results of TIGHT-K to be broadly applicable.
“There is no physiological basis to expect a different result in patients undergoing different types of cardiac surgery,” he said.
The primary endpoint was clinically and electrocardiography confirmed new-onset atrial fibrillation that occurred in the 5 days after the bypass procedure.
For the primary atrial fibrillation endpoint, event rates were similar in the tight-control and the relaxed-control groups (26.2% vs 27.8%); the 1.7% difference did not approach statistical significance (P = .44). The difference in dysrhythmias other than atrial fibrillation, although numerically lower in the tight-control group, was also not significant (19.1% vs 21.1%; P = .26).
There were no significant differences in several secondary endpoints, including length of hospital stay and in-patient mortality, but cost, a prespecified secondary endpoint, was approximately $120 lower per patient in the relaxed-control group than in the tight-control group (P < .001).
Lowering Cost Across Cardiac Surgeries
During the 5-day follow-up, median potassium levels were higher in the tight-control group. Levels in both groups fell gradually, but essentially in parallel, over the study period, so median potassium levels were always higher in the tight-control group than in the relaxed-control group. At the end of the observation period, mean potassium levels were 4.34 mEq/L in the tight-control group and 4.08 mEq/L in the relaxed-control group.
Prior to the development of atrial fibrillation, participants in the tight-control group received a medium of seven potassium administrations (range, 4-12), whereas those in the relaxed-control group received a medium of zero.
There were no significant differences in episodes in any subgroup evaluated, including those divided by age, sex, baseline left ventricular ejection fraction, and the absence or presence of beta blockers or loop diuretics. A per-protocol analysis also failed to show any advantage for tight potassium control.
Atrial fibrillation occurs in about one third of patients after bypass surgery, as it does after many types of cardiac surgery. Institutions often have strategies in place to reduce the risk after cardiac surgery, and potassium supplementation is one of the most common, despite the lack of supportive evidence, Dr. O’Brien said.