Relief of congestion is the primary goal of initial therapy for acute decompensated heart failure (ADHF). Early measurement of urine sodium concentration (UNa) may be useful to identify patients with diminished response to diuretics. The aim of this study was to determine if the first spot UNa after diuretic initiation could select patients likely to require more intensive therapy during hospitalization.

At the time of admission, 103 patients with ADHF were identified prospectively, and UNa was measured after the first dose of intravenous diuretic. Clinical outcomes were compared for patients with UNa >60 mmol/L and UNa of ≤60 mmol/L, with the primary outcome of a composite of death at 90 days, mechanical circulatory support during admission, and requirement of inotropic support at discharge.

Patients with UNa ≤60 had lower admission blood pressure, had less chronic neurohormonal antagonist prior to admission, and were more than twice as likely to experience the primary end point (hazard ratio 2.40, 95% CI 1.02-5.66, P = .045), which was marginally significant after adjusting for renal function and baseline home loop diuretic. Worsening renal function was significantly more common in patients with UNa <60 (23.6% vs 6.5%, P = .05). Although the initial assessment of congestion was similar at admission, patients with low early UNa had a longer length of stay (11 vs 6 days, P < .006) than patients with UNa >60.

Assessment of spot UNa after initial intravenous loop diuretic administration may facilitate identification and triage of a population of HF patients at increased risk for adverse events and prolonged hospitalization.