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.