Abbreviated two sample, single pool, variable volume urea kinetic modeling.

Abstract

A two-point model has been developed that uses actual predialysis (C0) and postdialysis (C1) blood urea nitrogen (BUN) values, and calculates the third value (C2) by forcing a solution for urea generation (Gurea) and urea volume of distribution (Vurea) that results in a predialysis BUN value a week later (C7) similar to C0. This two-point model was evaluated in 64 patients (mean age: 59 +/- 17 years) undergoing thrice weekly chronic hemodialysis, with mean predialysis (C0) and postdialysis (C1) midweek BUN values of 70 +/- 16 and 28 +/- 10 mg/dl, respectively. Compared to the standard three-point, single pool, variable volume standard, the two-point model accurately predicted Kt/V (1.08 +/- 0.22 versus 1.08 +/- 0.23, respectively) and Vurea (48.1 +/- 14.1 versus 48.1 +/- 13.9 L, respectively). The model also approximated C2 concentrations within an 11% range (66 +/- 20 versus 69 +/- 16 mg/dl for modeled and actual, respectively; p = 0.007) that allowed useful estimates of Gurea (6.64 +/- 1.87 versus 6.71 +/- 2.47 g/min for model and actual, respectively) and normalized protein catabolic rate (0.94 +/- 0.19 versus 0.94 +/- 0.26 for modeled and actual, respectively; p = ns). It is concluded that the two-point model described may be used for calculation of Kt/V and normalized protein catabolic rate in the clinical setting when a third BUN value is not available.