Evaluation of intradialytic solute and fluid kinetics - Setting up a predictive mathematical model

A mathematical model of solute kinetics for the improvement of hemodialysis treatment is presented, It includes a two-compartment description of the m ain solutes and a three-compartment model of body fluids (plasma, interstit ial and intracellular). The main model parameters can be individually assig ned a priori, on the basis of body weight and plasma concentration values m easured before beginning the session. Model predictions are compared with c linical data obtained in vivo during 11 different hemodialysis sessions per formed on 6 patients with a profiled sodium concentration in the dialysate and a profiled ultrafiltration rate. In all cases, the agreement between th e time pattern of model solute concentrations in plasma and the in vivo dat a proves fairly good as to urea, sodium, chloride, potassium and bicarbonat e kinetics, Only in two sessions was blood volume directly measured in the patient, and in both cases the agreement with model predictions was good. I n conclusion, the model allows a priori computation of the amount of sodium removed during hemodialysis, and makes it possible to predict the plasma v olume changes and plasma osmolarity changes induced by a given sodium conce ntration profile in the dialysate and by a given ultrafiltration profile. H ence, it can be used to improve clinical tolerance to the dialysis session taking the characteristics of individual patients into account, in order to minimize intradialytic hypotension, Copyright (C) 2000 S. Karger AG, Basel .