A SIMPLE MATHEMATICAL-MODEL APPLIED TO SELECTION OF THE SODIUM PROFILE DURING PROFILED HEMODIALYSIS

Background, Among dialysis patients in the last 10 years the incidence of intradialytic dysequilibrium syndrome and symptomatic hypotension has increased significantly. Profiled haemodialysis (PHD), a new dialy sis technique based on intradialytic modulation of the dialysate sodiu m concentration according to pre-elaborated individual profiles, has b een set up to reduce intradialytic imbalances and the incidence of dys equilibrium syndrome and symptomatic hypotension. The present paper il lustrates a new mathaematical model for solute kinetics, single-compar tment for sodium and two-compartment for urea, aimed at improving the use of PHD. The model allows the sodium profile to be elaborated a pri ori, before each dialysis session, according to the patient's clinical needs and respecting the individual sodium mass removal and weight ga in. Method. The mathaematical model was first derived and then applied to determining a rational dialysate sodium profile. A procedure which allows the method to be tuned to individual clinical needs on the bas is of routine measurements performed before each session is also prese nted. The proposed method was validated in vivo during seven dialysis sessions, each performed on a different patient. Results. The comparis on between data predicted by the model and those obtained in vivo show s a good correspondence in particular concerning the time pattern of b lood urea and sodium. The comparison between the model prediction and in vivo determined sodium and urea plasma curves showed standard devia tions (2.25 mEq/l for sodium and 0.87 mmol/l for urea) only slightly h igher than those attributable to laboratory measurement errors. Moreov er, in vivo implementation of PHD by our model enables one to remove a n amount of sodium mass comparable with the a priori quantity predicte d by the model.