Usefulness of natriuresis to predict in-hospital diuretic resistance

Background: Urinary sodium excretion predicts long term adverse events after discharge in patients with acute heart failure (AHF). The role of natriuresis as an early marker of poor diuretic response during an AHF episode has been scarcely investigated. We sought to evaluate whether early natriuresis or its change during heart failure hospitalization is associated with the development of in-hospital diuretic resistance (DR). Methods: This was a prospective, observational single center study of consecutive patients with AHF. Urine electrolytes were estimated from a spot urine sample within the first 6 hours following the first diuretic dose and 48 hours after admission. In-hospital DR was defined as poor diuretic response based on diuretic efficiency metrics and persistent congestion despite an intensive diuretic protocol. Results: Between January and December 2018, 143 patients were admitted for AHF. Of these, 102 fulfilled the inclusion criteria (60% males, median age 77 years [interquartile range [IQR]: 69-83), and 20 patients (19.6%) met the definition of DR. Early natriuresis was lower in patients with DR than in non-resistant patients (46 mEq/L [IQR: 38.5-80.0] vs 97.5 mEq/L [IQR: 70.5-113.5], P<0.001). Urinary sodium <50 mEq/L increased the risk of developing in-hospital DR (risk ratio: 5.011 [95% confidence interval 2.408 10.429], P<0.001). The area under the receiver operating characteristic curve for early natriuresis to predict DR was 0.791 (95% confidence interval 0.681-0.902, P<0.001). Conclusions: Initial natriuresis can predict in-hospital DR. Patients with urinary sodium <50 mEq/L have an increased risk of early resistance to diuretic treatment.