Abstract 19099: The Fractional Excretion of Urea is Substantially Altered by Diuretics in Heart Failure Patients: Implications for its Use in the Evaluation of Worsening Renal Function
Background: In the setting of acute decompensated heart failure (ADHF), significant renal dysfunction (RD) is a common both at presentation and during treatment. The fractional excretion of urea (FeUrea) is often recommended to differentiate “pre-renal” from intrinsic RD in patients receiving diuretics. However, the intra-renal physiology regulating urea reabsorption theoretically should be affected by high dose loop diuretics which are commonly utilized in ADHF.
Methods: Heart failure patients presenting to the Yale Transition Care Clinic who received treatment with loop diuretics were enrolled (n=64). Urine was collected at baseline and 60-90 minutes following administration of loop diuretics. Possible AKI was defined as a presenting serum creatinine ≥0.3 mg/dl above the lowest outpatient level in the prior 12 months.
Results: Overall, 75.9% of the cohort had an estimated glomerular filtration rate < 60 ml/min/1.73m^2 and 66.7% met criteria for possible AKI. As would be expected in a sodium avid HF population, the mean pre-diuretic FeUrea was 31.9 ± 10.2%. This was below the “pre-renal” FeUrea cutoff (<35%) in 62.5% of patients. Following administration of 160 mg (50 to 280) of IV furosemide equivalents, FeUrea increased by an average of 7.3 ±8.5% (p<0.0001). After diuretics, the percentage of patients with a “pre-renal” FeUrea decreased to 37.7% which translated into 42.5% of initially “pre-renal” patients no longer being classified as “pre-renal.” The change in FeUrea was unrelated to the diuretic induced urine output (r=0.19 p=0.14) or the dose of diuretic (r=0.17, p=0.20). There was significant individual variability in the change in FeUrea induced by loop diuretics (Figure) such that a loop diuretic “correction factor” would not be appropriate.
Conclusion: Contrary to traditional wisdom, FeUrea does not appear to be a reliable tool to workup changes in renal function in ADHF patients receiving treatment with high dose loop diuretics.
Author Disclosures: S.J. Cheng: None. O. Laur: None. A.J. Kula: None. C.O. Onyebeke: None. S.G. Coca: None. M.A. Perazella: None. J.M. Testani: None.
- © 2014 by American Heart Association, Inc.