Correlates of Urea Kinetic Modeling during Hemodialysis in Patients with Acute Renal Failure

Abstract

The current guidelines on dialysis adequacy in acute renal failure (ARF) are loosely defined and have been extrapolated from patients with end-stage renal disease. The objectives of this study were (1) to compare three methods of urea kinetic modeling measurement in patients with ARF receiving intermittent hemodialysis, (2) to compare prescribed to delivered dose of dialysis, and (3) to explore the factors that are associated with dialysis delivery. ‘Single-pool’ urea kinetic modeling was assessed by the Ureakin^® software and the second-generation equation which uses a logarithmic estimate of spKt/V. ‘Equilibrated’ Kt/V (eKt/V) was calculated using the rate adjustment equation. The prescribed dose was derived using the manufacturer’s specifications of the dialyzer clearance, prescribed time, actual delivered blood and dialysate flow, and estimates of volume of urea distribution. A total of 78 consecutive spKt/V measurements were obtained in 24 patients. The mean urea reduction ratio was 51 ± 1%. The delivered spKt/V was significantly lower than that prescribed (0.87 ± 0.03 or 0.83 ± 0.03 vs. 1.28 ± 0.05; p = 0.0001). The equilibrated Kt/V was markedly lower than the delivered spKt/V (0.73 ± 0.03 vs. 0.83 ± 0.03; p = 0.0001). Univariate analyses demonstrated that female gender, low body mass index, low predialysis weight, use of cellulose acetate dialyzers, and increased prescribed time were associated with increased odds of prescribed spKt/V ≧1.2. Similarly, old age, increased delivered time, and high cytokine production were associated with increased odds of delivered spKt/V ≧1.2. In summary, while the impact of delivered intermittent hemodialysis on the survival of patients with ARF remains to be determined, these results indicate that dialysis delivery is suboptimal in ARF, and empiric dosing should strongly consider factors related to lean body mass, including age and gender.