Examining the "Repletion Reflex": The Association between Serum Potassium and Outcomes in Hospitalized Patients with Heart Failure

J Hosp Med. 2019 Dec 1;14(12):729-736. doi: 10.12788/jhm.3270. Epub 2019 Jul 24.

Abstract

Background: In patients hospitalized with heart failure (HF) exacerbations, physicians routinely supplement potassium to maintain levels ≥4.0 mEq/L. The evidence basis for this practice is relatively weak. We aimed to evaluate the association between serum potassium levels and outcomes in patients hospitalized with HF.

Methods: We identified patients admitted with acute HF exacerbations to hospitals that contributed to an electronic health record-derived dataset. In a subset of patients with normal admission serum potassium (3.5-5.0 mEq/L), we averaged serum potassium values during a 72-hour exposure window and categorized as follows: <4.0 mEq/L (low normal), 4.0-4.5 mEq/L (medium normal), and >4.5 mEq/L (high normal). We created multivariable models examining associations between these categories and outcomes.

Results: We included 4,995 patients: 2,080 (41.6%), 2,326 (46.6%), and 589 (11.8%) in the <4.0, 4.0-4.5, and >4.5 mEq/L cohorts, respectively. After adjustment for demographics, comorbidities, and presenting severity, we observed no difference in outcomes between the low and medium normal groups. Compared to patients with levels <4.0 mEq/L, patients with a potassium level of >4.5 mEq/L had a longer length of stay (median of 0.6 days; 95% CI = 0.1 to 1.0) but did not have statistically significant increases in mortality (OR [odds ratio] = 1.51; 95% CI = 0.97 to 2.36) or transfers to the intensive care unit (OR = 1.78; 95% CI = 0.98 to 3.26).

Conclusions: Inpatients with heart failure who had mean serum potassium levels of <4.0 showed similar outcomes to those with mean serum potassium values of 4.0-4.5. Compared with mean serum potassium level of <4.0, mean serum levels of >4.5 may be associated with increased risk of poor outcomes.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Aged
  • Aged, 80 and over
  • Biomarkers / blood
  • Female
  • Heart Failure / blood*
  • Heart Failure / drug therapy*
  • Heart Failure / mortality
  • Hospital Mortality / trends
  • Hospitalization / trends*
  • Humans
  • Length of Stay / trends
  • Male
  • Middle Aged
  • Potassium / administration & dosage*
  • Potassium / blood*
  • Retrospective Studies
  • Treatment Outcome

Substances

  • Biomarkers
  • Potassium