DEVELOPMENT AND CRITICAL-EVALUATION OF AN IMPROVED COMPREHENSIVE MULTICOMPARTMENT MODEL FOR THE EXCHANGE PROCESSES DURING HEMODIALYSIS

An improved comprehensive multicompartment model for the simulation of the most important metabolic state variables in the patient during di alysis is presented. With this approach time courses of urea, creatini ne, K+, Na+, Cl-, HCO3-, H+ and CO2 can be predicted. Additionally, os motic water shifts as well as resting membrane potentials are calculat ed. The model contains the following extensions compared to classical approaches: For the calculation of osmotic water shifts, not only sodi um, but also urea, potassium, chloride and unspecified indiffusable io ns are taken into account. Furthermore, hemodynamic aspects are consid ered by assuming two tissue groups with different perfusion. Thus it i s possible to estimate the influence of hemodynamic parameters (e.g. c ardiac output or blood flow distribution) on the exchange processes. T he model can be adjusted individually by several system parameters. Th is adjustment is performed by minimizing the sum of the quadratic diff erences between simulated and measured plasma concentrations of the co nsidered substances. A first validation has been performed successfull y with measured data from 18 dialysis patients. After the effective wh ole-body exchange area of the resting cell membranes for potassium, so dium and chloride had been estimated, rebound effects for those electr olytes could be simulated successfully.