The combined impact of hyponatremia and hematocrit on the risk for 90-day readmission and death in patients with heart failure: dilutional hyponatremia versus depletional hyponatremia

BACKGROUND: Hyponatremia is common in hospitalized patients with heart failure (HF) and predicts a poor prognosis after discharge. In general, hyponatremia can be divided into two types: dilutional or depletional. OBJECTIVE: Assess the impact of hyponatremia type on short-term outcomes. DESIGN: Retrospective cohort SETTINGS: Single center in China PATIENTS AND METHODS: We sorted patients by hyponatremia into two types: dilutional hyponatremia (DiH, with hematocrit <35%) and depletional hyponatremia (DeH, with hematocrit ≥35%). The Kaplan-Meier method and Cox regression analysis were used to identify the impact of hyponatremia types on the risk for 90-day readmission and death. MAIN OUTCOME MEASURES: 90-day readmission and death combined. SAMPLE SIZE: 1770 patients. RESULTS: Hyponatremia was present in 324/1770 patients with 182 cases classified as DiH versus 142 as DeH. Kaplan-Meier analyses showed a higher incidence of poor short-term outcomes in hyponatremia compared with normonatremia (log-rank P<.001), and the risk was higher in DiH than DeH although the difference was not statistically significant (log-rank P=.656). Multivariate Cox regression analyses showed that only DiH was independently associated with short-term outcomes (HR=1.34, 95%CI: 1.02-1.77, P=.038), but not DeH (HR=1.32, 95%CI: 0.97-1.80, P=.081). Analysis of the secondary endpoints showed that DiH increased the risk of readmission but not death (HR=1.36, P=.035 for readmission; HR=1.13, P=.831 for all-cause death). CONCLUSIONS: Low hematocrit, rather than high hematocrit, with hyponatremia was associated with a risk of 90-day readmission in patients with HF. LIMITATIONS: Single center, nonrandomized. CONFLICT OF INTEREST: None.