OBJECTIVE: The study objective was to compare the 30-day readmission rate and mortality between patients with heart failure who have persistent hyponatremia during hospitalization and patients who have their admission hyponatremia corrected before discharge.
METHODS: This large retrospective cohort study included all adult patients admitted with a diagnosis of congestive heart failure to a tertiary-care hospital between July 2003 and October 2009. We compared the readmission rate and mortality 30 days after discharge between patients with persistent hyponatremia (ie, low sodium level at both admission and discharge) and patients with hyponatremia correction during hospitalization.
RESULTS: Among the 4295 eligible patients with hyponatremia at admission, 1799 (41.9%) did not have their sodium level corrected at discharge. Overall, 1269 patients (29.5%) had a 30-day unplanned readmission or died. In a multivariable logistic regression analysis, the absence of hyponatremia correction was associated with a 45% increase in the odds of having a 30-day unplanned readmission or death (odds ratio, 1.45; 95% confidence interval, 1.27-1.67). Among patients with persistent hyponatremia, those with more severe hyponatremia at discharge (<130 mm/L) had a higher odds (odds ratio, 1.68; 95% confidence interval, 1.32-2.14) of having a 30-day readmission or death than those with less severe hyponatremia at discharge (130-134 mm/L).
CONCLUSIONS: The absence of correction of hyponatremia over the course of hospitalization was frequent and independently associated with an increase of approximately 50% in the odds of having a 30-day unplanned readmission or death. This association appeared to be independent of heart failure severity.