A model of the patient-dialysis treatment to study the dynamics of metabolic waste concentrations and c.s.f. pressure, and hence to provide guidelines for treatment

Abstract

A patient-dialysis treatment analysis has been performed, to study the dynamics of metabolic waster concentrations (urea and creatinine) and c.f.s. pressure in a renal patient during the entire cycle of pre-dialysis, dialysis and post-dialysis periods. The concentrations have predicted by the five compartment model of Dedrick and Bischoff, for the dialysis treatment variables, such as frequency of use and treatment time, urea generation rate of the patient and urea clearance rate of the dialyser. The results indicate that the c.f.s. pressure decreases during the pre-dialysis period, increases abruptly at the beginning of the treatment and then approaches (but does not overshoot) its normal value gradually. The analysis thereby shows that the significant rise in c.f.s. pressure in the rapid haemodialysis is not due to changes in the urea concentrations in the brain, which is validated by the pathophysiology studies of dialysis disequilibrium syndrome by Arieff and Massry. If the large abrupt rise in c.f.s. pressure (immediately following the start of treatment) is not desirable, it is recommended that the dialysis be started at the lowest urea clearance rate. Later a gradual increase in the clearance rate may be provided and the treatment frequency can be increased, in order to limit the duration of a treatment session.