The role of urine sodium in acutely decompensated heart failure.

Background: Diuretic resistance is common and results in poor outcome. Spot urine sodium (UrNa) is suggested as a tool to tailor diuretics and improve efficacy of therapy. We prospectively evaluate the prevalence of diuretic resistance, predictors of low spot-UrNa and the prognostic value of spot-UrNa in an unselected ADHF population. Methods: Patients admitted for ADHF and treated with iv diuretics were included. Spot-UrNa was collected 2 h after administration of an IV diuretic bolus. The main endpoint was a composite of HF re-hospitalizations and all-cause mortality at 90 days follow-up. Results: 143 patients were included in this study (median age 81 [75 - 85] years, 55 % male), of which 50 % were newly diagnosed with HF. Low spot-UrNa was independently associated with worse renal function, low serum sodium, and systolic blood pressure, previous loop diuretic and SGLT2i use and loop diuretic administered dose. Both absolute spot-UrNa (HR 0.87, 95 % CI 0.79 - 0.95, P=0.003 per 10 mmol/L increase) and a urinary sodium ≥ 100 mmol/l (HR=0.51, 95 % CI 0.27 - 0.97, P=0.04) significantly predicted the composite endpoint. This association was no longer significant after correction for confounders. Patients with low spot-UrNa attained longer IV diuretic treatment and a higher cumulative IV diuretic dose. Conclusions: Spot-UrNa is prevalent and occurs more often in patients with more progressed cardio-renal disease. Spot-UrNa significantly predicts 90-day HF hospital-free survival in ADHF. Further studies are needed evaluating the effect of UrNa guided diuretic treatment on clinical endpoints.