Multicompartment urea kinetics in well-dialyzed children. mum delivered K d t/V of 1.2 [1]. Extrapolation from adult Background. We have reported catch-up growth with hemostudies may be problematic, as more appropriate pediatdialysis (HD) of approximately 15 hours/week. Without an ric outcome measures-such as growth, school perforequilibrated post-treatment blood urea nitrogen, the variablemance, or pubertal development-might lead to very volume single-pool (VVSP) model will not account for urea different conclusions as to the relative importance of rebound, inflating the estimated HD dose (K d t/V). A two-pool model (FVDP) predicts rebound, but requires fixed compartthe small molecular weight toxins for which urea is a ment volumes for the equations to be solvable in closed form, surrogate marker. Prior to the introduction of recombialso inflating K d t/V. nant human growth hormone (rhGH), the mean annual Methods. We developed an approximate perturbation soluloss in height standard-deviation score (⌬HSDS) in pretion (WKB method) to a variable volume, two-pool (VVDP) pubertal HD patients was Ϫ0.4 to Ϫ0.8 SD/year [2]. model. Estimated model parameters were compared with the results of equilibrated kinetic studies using measured clearance However, we have recently described normal growth K d (N ϭ 17). Once the model was validated, we re-analyzed rates, catch-up growth, and normal puberty with inten-292 kinetic studies from our earlier cohort, which was considsive nutritional support and HD clearance in prepubertal ered well-dialyzed on the basis of growth rates (N ϭ 12, mean patients treated without rhGH [3]. With a weekly treatannual change in height standard deviation score ϩ0.31, mean ment time of approximately 15 hours and a single-pool follow-up of 26 months). Results. For the VVSP, FVDP, and VVDP models, respecurea K d t/V of approximately 2.0, the mean annual tively, the mean errors were (1) K d t/V, 0.22 Ϯ 0.07, 0.29 Ϯ ⌬HSDS was Ͼϩ0.3 SD/year, and predicted final adult 0.17, 0.06 Ϯ 0.07 (ANOVA, P Ͻ 0.001); (2) urea distribution height fell generally within 2 SD of genetic potential.
