Simulation analysis of the influence of hemodialysis control parameters on exchange processes during therapy.

The effect of dialysis control parameters (dialysate composition, ultrafiltration rate, blood flow rate) on the patient's internal milieu were studied using a mathematical model for the description of the dynamic exchange processes during hemodialysis. This model simulates the electrolyte and water distribution, the acid-base and the oxygenation state as well as the ventilation. The dialysate sodium concentration affects mainly the intra-/extracellular water and the potassium distribution. The dialysate bicarbonate and acetate concentrations control the acid-base state and the electrolyte distribution (sodium and potassium). In addition, the dialysate acetate concentration has a strong effect on arterial oxygenation and on ventilation. The ultrafiltration rate controls the water distribution between plasma and the interstitial space but also the sodium distribution and the arterial acid-base state. The blood flow rate through the dialyser influences the acid-base state and, by this, it affects the potassium and sodium distribution. The acid-base state is affected in opposite directions when acetate or bicarbonate is used as a buffer.