Urinary sodium: worth its salt?

Persistent congestion during hospitalization for heart failure (HF) is associated with adverse outcomes.1 Loop diuretics treat congestion in HF, but the diuretic response varies between individuals and remains challenging to assess. Typically, clinicians rely on a combination of symptoms and signs, including, weight loss, and urine volume to assess treatment response.2 However, the recorded weight loss and urine volume are frequently inaccurate and may be logistically difficult to obtain.3,4 An emerging tool to measure the diuretic response is urinary sodium, which can be measured as a timed collection or taken as a spot measurement. In the most recent position statement on diuretics from the Heart Failure Association of the European Society of Cardiology (ESC)5 and the most recent ESC HF guidelines,6 the use of spot urinary sodium was recommended on the basis of prior observational data to identify patients with inadequate diuretic response. However, the magnitude of the association between urinary sodium and outcomes has not previously been characterized.