Fractional Excretion of Urate for Diuresis Management in Heart Failure and Cardiorenal Syndrome

Abstract

Most heart failure hospitalizations are due to volume overload; however, it is not easily evaluated by physical examination. Avoidance of diuresis in patients with fluid overload to avoid acute kidney injury increases morbidity in heart failure. We hypothesize that fractional excretion of urate can be used to guide diuresis. (Level of Difficulty: Advanced.).

Keywords: AKI, acute kidney injury; AS, aortic stenosis; BNP, brain natriuretic peptide; CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; CRS; CXR, chest x-ray; DOE, dyspnea on exertion; ECFV, extracellular fluid volume; ED, emergency department; EF, ejection fraction; FeNa; FeUa; FeUa, fractional excretion of uric acid; HF, heart failure; HFrEF, heart failure with reduced ejection fraction; ILD, interstitial lung disease; IV, intravenous; PE, physical examination; SOB, shortness of breath; diuresis; uric acid; volume overload.

Graphical abstract

Figure 1

Proposed Assessment of Volume Overload Using Fractional Excretion of Uric Acid We hypothesize that fractional excretion of uric acid >8% indicates loop diuretic responsive fluid overload with low probability of diuretic-induced kidney injury with continued diuresis. ∗Volume overload is defined by clinically determined expansion of interstitial volume (leg swelling, ascites, pleural effusion) or intravascular volume (right atrial pressure elevation by JVD/inferior vena cava plethora using ultrasound, left atrial pressure elevation [lung ultrasound, crackles] and hemodynamic congestion [B-type natriuretic peptide elevation]). †Diuretic-responsive CHF: expansion of interstitial/intravascular fluid space in setting of elevated ventricular transmural pressure due to abnormal cardiac function, responsive to diuretic agents with low probability of inducing acute kidney injury. ‡Low-flow state: decreased renal blood flow due to low cardiac output (cardiac index <2.5 l/min/m²) or cold extremities/lactate elevation. CHF = congestive heart failure; SIADH = syndrome of inappropriate anti-diuretic hormone.