Low sodium excretion after diuretics associated with all-cause mortality in acute HF
Clinical importance of urinary sodium excretion in acute heart failure
Introduction and methods
Treatment of acute heart failure (AHF) is focused on alleviation of congestion, volume overload, and shortening of hospital stay [1,2]. Most of the decongestion is achieved early after admission and decreased in the following days. 25% Of patients have residual signs of congestion at discharge . A rigorous and quick diuretic response is associated with improved outcomes. However, it has been proven difficult to assess the treatment effect of diuretics by evaluating congestion status after start of therapy [4-7].
An Heart Failure Association ESC consensus paper has proposed to study spot urinary sodium and/or diuresis very early after initiation of diuretics, and to intensify or expand (loop) diuretic treatment if natriuresis or diuresis are insufficient . This single-center prospective study aimed to investigate the clinical importance of urinary sodium excretion in AHF patients.
The diagnosis of AHF was based on the ESC heart failure guidelines  and enrolled patients (n=175, mean age was 71±14 years, 44% were female) presented with signs and symptoms of congestion, requiring intravenous diuretic therapy. Patients received intravenous vasodilators when systolic blood pressure was >110 mmHg at admission and all patients received bumetanide as the preferred loop diuretic (dose was determined by the treating physician). Urinary volume and urinary sodium were measured from urine collected in the following time frames: 0-6h, 6-24h, 24-48h, 48-72h, and 72-96h after diuretic initiation. The variable of interest was urinary sodium excretion in the first 6 hours after diuretic initiation (urinary sodium concentration x urinary volume over 6h).
The primary clinical endpoint was all-cause mortality after admission. Secondary endpoints included HF rehospitalization after discharge and a combined endpoint of first occurrence of all-cause mortality and/or HF rehospitalization. The median follow-up was 257 (152-427) days.
- Median urinary sodium excretion was 130 (67-229) mmol in the first 6h after intravenous diuretic initiation, 347 (211-526) mmol between 6-24h, 181 (94-270) mmol between 24-48h, 126 (74-194) mmol between 48-72h, and 114 (73-160) mmol between 72-96h.
- Urinary sodium excretion after 6h was a predictor of total urinary volume after 24h (P<0.001). In the lowest tertile of urinary sodium excretion at 6 h, only 27% of patients achieved >3L diuresis after 24 h, vs. 73% and 94% in the middle and highest tertile.
- Urinary sodium excretion after 6h was associated with all-cause mortality (HR 1.05, 95%CI 1.02–1.08, P=0.001 per 10 mmol decrease in urinary sodium excretion). When stratified for tertiles of urinary sodium excretion at 6h, the HR was 3.81 (95% CI 1.92–7.57, P <0.001) for the lowest vs. the highest tertile.
- Urinary volume and urinary sodium concentration at 6 hours were also predictors of all-cause mortality (HR 1.05, 95%CI 1.01–1.08, P = 0.007 per 100 mL decrease in urine output and HR 1.16, 95%CI 1.06–1.26, P = 0.001 per 10 mmol/L decrease in urinary sodium excretion).
- Urinary sodium excretion was not associated with HF hospitalization (HR 1.03, 95%CI 1.00-1.07, P=0.033 per 10 mmol decrease).
- Urinary sodium excretion was associated with the combined endpoint of all-cause mortality and heart failure rehospitalization (HR 1.04, 95% CI 1.01–1.07 per 10 mmol decrease, P = 0.005)
This prospective study in patients with AHF showed that low urinary sodium excretion during the first 6h after diuretic initiation was associated with lower urine volume in the first 24h, and with all-cause mortality.
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