Rapid and Accurate Assessment of Diuretic Response: Validation of an Equation to Predict Diuretic Induced Sodium Output Using a Spot Urine Sample

Abstract

Introduction Diuretic response is generally assessed using crude measures such as fluid or weight loss which are usually reported in a delayed manner (e.g. the change in weight from one day to the next). This in turn restricts clinicians’ ability to titrate diuretics. These established metrics have poor correlation with one another and they do not predict outcomes as well as cumulative sodium excretion. However, a 24h urine collection is difficult to perform even in a clinical trial, much less in routine clinical practice. It also does not address the lag time between diuretic administration and assessment of response. We previously reported proof of concept results on an equation to estimate sodium excretion based on a post-diuretic spot urine sample. Our current objective was to validate this equation in a real-world sample of patients undergoing IV diuretic therapy. Hypothesis Cumulative sodium output from a loop diuretic can be predicted using a spot urine sample. Methods The validation cohort consisted of 286 hospitalized patients receiving IV diuretics. Our equation is shown below (Figure). The validation cohort consisted of 286 hospitalized patients receiving IV diuretics. Urine collections were performed under intense supervision by a study coordinator. A spot urine was obtained at 1h, 2h post diuretic administration, and a cumulative 6h urine collection was used to determine total sodium. We used the 2h value for the equation. We defined a poor diuretic response as Results The predicted sodium equation had the best receiver operating characteristics (AUC = 0.92, 95% CI = 0.88 to 0.96, p Conclusions Our natriuretic response equation provides a faster and more accurate estimation of sodium excretion following a diuretic dose than either net fluid loss or weight change. This may aid in more rapid assessment of diuretic response and ultimately dose titration.