Serum potassium repletion for mild abnormalities didn't affect outcomes in heart failure exacerbations

The retrospective study compared mortality, ICU transfers, and length of stay among patients with normal serum potassium levels at admission for heart failure by whether they had average levels of less than 4.0 mEq/L, 4.0 to 4.5 mEq/L, or greater than 4.5 mEq/L during hospitalization.

For patients hospitalized with heart failure, having a serum potassium level slightly above or below normal was not associated with any difference in outcomes, a recent study found.

The retrospective study used a 116-hospital database to analyze patients with an admission for acute heart failure exacerbation lasting more than 72 hours between January 2010 and December 2012. It focused on the subset of 4,995 patients with serum potassium levels of 3.5 to 5.0 mEq/L at admission and looked at their average serum potassium values during a 72-hour window of hospitalization. Results were published by the Journal of Hospital Medicine on July 24.

The 72-hour average was less than 4.0 mEq/L in 41.6% of the patients, 4.0 to 4.5 mEq/L in 46.6%, and greater than 4.5 mEq/L in 11.8%, which the researchers categorized as low normal, medium normal, and high normal, respectively. After adjustment for demographics, comorbidities, and severity of illness, there was no difference in mortality, ICU transfers, or length of stay between the low- and medium-normal groups. Compared to the low-normal group, the high-normal group had a longer length of stay (median difference, 0.6 day; 95% CI, 0.1 to 1.0 day) but didn't have statistically significant increases in mortality (odds ratio [OR], 1.51; 95% CI, 0.97 to 2.36) or ICU transfers (OR, 1.78; 95% CI, 0.98 to 3.26).

The study authors noted that many physicians reflexively replete potassium in heart failure patients to a serum value of greater than 4.0 mEq/L. “However, daily potassium repletion represents a huge cost in time, money, and effort to the health system,” they wrote. Based on this study and previous research, the benefit of maintaining a serum potassium level of at least 4.0 mEq/L during heart failure hospitalization is unclear, the authors said. There may even be some risk for worse outcomes with levels above 4.5 mEq/L. However, the authors cautioned that unobserved differences in the study patients with higher potassium levels might have been responsible for their worse outcomes. The study was limited by its retrospective design as well as lack of data on arrhythmias as an outcome and potential effects of changes in practice since 2012.

An accompanying editorial noted that there is no consensus on the use of potassium repletion during hospitalization for a heart failure exacerbation. It called the study “some of the strongest evidence to date that a potassium goal of >4 mEq/L may not be efficacious” in reducing complications in such patients. Both the study and the editorial called for randomized trials to further explore this question.