Prediction and measurement of diuretic responsiveness after oral administration of furosemide to healthy dogs and dogs with congestive heart failure

Background In human patients, cumulative urine volume (uVol) and urine sodium (uNa) can be predicted using spot urine samples and these quantitative measures help detect low diuretic responsiveness (LDR). Hypothesis/objectives Formulas using spot urine samples predict cumulative uVol and uNa output after oral administration of furosemide to dogs. Animals Eight healthy dogs, 6 dogs with congestive heart failure (CHF). Methods Prospective interventional study. Spot urine samples at 180 and 270 minutes after furosemide (3 mg/kg PO) were used to predict cumulative uVol and uNa output over 7 hours. Differentiation of dogs fulfilling predefined criteria for LDR was examined using receiver operating characteristic (ROC) curves. Results Predicted uNa output at 180 minutes (r(s) = 0.763, [95% confidence interval [CI], 0.375-0.923], P = .002) and 270 minutes (r = 0.816, [95% CI, 0.503-0.940], P < .001) was highly correlated to 7-hour uNa output. Predicted uVol at 180 minutes (r = 0.598, [95% CI, 0.098-0.857], P = .02) and 270 minutes (r = 0.791, [95% CI, 0.450-0.931], P < .001) was moderately correlated to 7-hour uVol. Predicted uNa using 180-minute (area under the curve [AUC], 0.933 [95% CI, 0.804-1.000]) and 270-minute (AUC, 0.911 [95% CI, 0.756-1.000]) samples identified dogs with LDR (n = 5) with high accuracy. Conclusions and Clinical Importance Urinary Na excretion and uVol are complementary but distinct aspects of diuretic responsiveness in dogs. Quantification of diuretic responsiveness in the clinical setting opens new diagnostic, treatment, and monitoring strategies.