Prediction of solute kinetics, acid-base status, and blood volume changes during profiled hemodialysis

A mathematical model of solute kinetics oriented to the simulation of hemod ialysis is presented. It includes a three-compartment model of body fluids (plasma, interstitial and intracellular). a two-compartment description of the main solutes (K+, Na+, Cl-, urea, HCO3-, H+), and acid-base equilibrium through two buffer systems (bicarbonate and noncarbonic buffers. Tentative values for the main model parameters can be given a priori, on the basis o f body weight and plasma concentration values measured before beginning the session. The model allows computation of the amount of sodium removed duri ng hemodialysis, and may enable the prediction of plasma volume and osmolar ity changes induced by a given sodium concentration profile in the dialysat e and by a given ultrafiltration profile. Model predictions are compared wi th clinical data obtained during 11 different profiled hemodialysis session s, both with all parameters assigned a priori, and after individual estimat ion of dialysances and mass-transfer coefficients. In most cases, the agree ment between the time pattern of model solute concentrations in plasma and clinical data was satisfactory, in two sessions, blood volume changes were directly measured in the patient, and in both cases the agreement with mode l predictions was acceptable. The present model can be used to improve the dialysis session taking some characteristics of individual patients into ac count, in order to minimize intradialytic unbalances (such as hypotension o r disequilibrium syndrome). (C) 2000 Biomedical Engineering Society. [S0090 -6964(00)01002-X].