Automatic hemodialysis prescriptions by urea kinetic modeling.

Abstract

Introduction Guidelines on hemodialysis (HD) dosing are based on urea kinetics, which can be modeled mathematically. Different schedules can be compared by equivalent continuous clearance. Methods A computer program generating HD prescriptions automatically was developed. In 200 actual HD urea kinetic modeling sessions involving 33 patients the urea distribution volume, generation rate, and concentration profile in the external space were computed using ionic dialysance as dialyzer clearance in the double pool ureakinetic model. Dialyzer in vivo mass area coefficient K0 A was calculated from online data with the Michaels' equation. Data from the modeling sessions were used for generating new prescriptions for the same patients. Findings New prescriptions meeting 12 criteria-technical limits and guideline targets-were generated by the model. They showed a wide range of basic treatment parameters (time and frequency, blood and dialysate flow, and ultrafiltration). In five cases, the dialysis time or frequency should have been increased from the actual to achieve the targets, in 72 cases the frequency could have been decreased. Two methods to emphasize RRF were tested. Using a coefficient of 2.0 for renal urea clearance in computing adjusted equivalent continuous clearance (EKR/Va ), as suggested by Casino and Basile, decreased further the required treatment frequency in incremental dialysis. Discussion The model produced plausible individual prescriptions, but some unknown factors caused the determination of the dialyzer in vivo K0 A to be inaccurate. The model must be tested with modern devices on patients before integration into dialysis machines and information systems.