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

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.

High‐Goal 'Lytes: Repletion Gone Awry?

“…Moreover, in a sensitivity analysis of patients who did not receive potassium supplementation, there remained statistically similar rates of mortality, ICU transfer, and LOS 3 . Together, these findings suggest that maintenance of potassium >4 mEq/L may not be efficacious for preventing in‐hospital complications of ADHF 3 . In fact, they observed more frequent mortality and ICU transfer in patients who had high‐normal potassium.…”

“…In fact, they observed more frequent mortality and ICU transfer in patients who had high‐normal potassium. This group, however, had a higher burden of chronic kidney disease and illness severity on presentation and was less likely to receive supplemental potassium 3 …”

“…Over the 72‐hour exposure window, the authors observed no statistically significant difference in mortality, ICU transfer, or LOS between the low‐normal and normal potassium groups 3 . Moreover, in a sensitivity analysis of patients who did not receive potassium supplementation, there remained statistically similar rates of mortality, ICU transfer, and LOS 3 .…”

“…In this issue of the Journal of Hospital Medicine , O'Sullivan et al explore the associations between mean 72‐hour serum potassium and important clinical outcomes—in‐hospital mortality, transfer to an intensive care unit (ICU), and length of stay (LOS)—among patients with normal admission serum potassium hospitalized for ADHF 3 . Through a retrospective review of electronic records from 116 hospitals, the authors identified 4,995 initially normokalemic heart failure (HF; identified by ICD‐9 codes) patients and grouped them into low‐normal (3.5‐4.0 mEq/L), normal (4.0‐4.5 mEq/L), and high‐normal (4.5‐5.0 mEq/L) potassium groups 3 . Adjustments were made for composite scores encapsulating other lab abnormalities and comorbidities.…”

“…Moreover, the authors do not have access to data regarding incident arrhythmia and instead use ICU admission as a surrogate. In addition, ADHF patients in this study varied greatly in illness severity, ranging from those receiving initial therapy with loop diuretics alone to those requiring augmentation with thiazides and even the use of temporary mechanical circulatory support 3 . Escalating loop diuretic or metolazone use not only is associated with increased mortality 6 but often results in impressive natriuresis and, potentially dangerous, kaliuresis secondary to the sequential nephron blockade 7 .…”