Programmed filtration, a new method for removing large molecules and regulating albumin leakage during hemodiafiltration treatment.

During hemodiafiltration (HDF) treatment for chronic renal failure patients, replacing large volumes using high-flux membranes with relatively large pores is preferred from the standpoint of enhancing the elimination of large molecules (10 to 50 kd). Aggressive protein-permeable treatment often results in massive leakage of essential albumin, however, which may cause fatigue, hypotension, and a decrease in the plasma albumin concentration in some patients. During 5-hour conventional HDF treatment with the filtration rate or pressure set at constant values, fractional albumin loss in the dialysate was assayed, which revealed that the albumin concentration in the dialysate showed a maximum value in the beginning with a steep decline within 1 hour. Approximately 40% to 50% of the total amount of albumin leakage occurred during the first 30 minutes. Concomitantly the large molecules transferred into the pores by aggressive filtration during the beginning partially plugged the pores, resulting in a decrease in the permeability for beta(2)-microglobulin. From the standpoint of achieving the highest clearance for large molecules, while suppressing albumin leakage below the acceptable range, the optimal profiles for filtration conditions in HDF have been proposed, in which either the transmembrane pressure is regulated according to the sigmoid curve in the pressure control manner or the flow rate is set along the concave in the flow control manner. The profiles of pressure or flow as a function of time have been programmed and installed in a HDF machine to perform an optimal HDF treatment automatically. The new filtration methods gave significantly higher beta(2)-microglobulin removal and lower albumin leakage than conventional HDF methods with constant filtration.