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J Hosp Med. 2019 Jul 24;14:E1-E8. doi: 10.12788/jhm.3270. [Epub ahead of print]

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

Author information

1
Institute for Healthcare Delivery and Population Science, University of Massachusetts Medical School-Baystate, Springfield, Massachusetts.
2
University of Massachusetts Medical School, Worcester, Massachusetts.
3
Department of Medicine, University of Massachusetts Medical School-Bay-state, Springfield, Massachusetts.
4
Division of Cardiology, Baystate Medical Center, Springfield, Massachusetts.
5
Epidemiology and Biostatistics Research Core, Office of Research, University of Massachusetts Medical School-Baystate, Springfield, Massachusetts.
6
University of Massachusetts-Amherst, Amherst, Massachusetts.

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.

PMID:
31339844
DOI:
10.12788/jhm.3270

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