MODEL-BASED DIALYSIS ADEQUACY PREDICTION BY CONTINUOUS DIALYSATE UREAMONITORING

A modeling approach for on-line estimation of urea kinetics from conti nuous measurement of urea concentration in the effluent dialysate stre am (DUN) is presented. On-line identification of urea kinetics respons e parameters is used to predict and update dialysis adequacy during th e treatment. Dialysis adequacy can be quantified in several ways, but its strict dependence on final urea concentration is a major fact. For this reason, a good predictive skill on the time course of DUN may en able better performances in the control of dialysis outcome by treatme nt parameters adjustment. A post-filter enzymatic sensor performs cont inuous measurement of DUN on patients undergoing standard haemodialysi s. To get an early prediction of the end dialysis urea level, the solu tion of a variable volume double-pool (VVDP) model is used, whose para meters are identified at each time on the basis of the past DUN histor y. Unlike the variable volume single-pool (VVSP) model, this enables a prompt and accurate estimation of the final DUN. In fact, after 75 mi n the estimates always differ by less than 10% from the values measure d by the sensor at the end of the treatment. Moreover, values predicte d by the model in the last hour always lie within 1% of measured final values. Realtime knowledge of an analytic expression for whole DUN ti me course also enables the accurate prediction of total removed urea, with no need of cumbersome dialysate collection techniques.