New Method of Blood Purification (Recycle Filtration System)

Object: We have developed a new blood purification system, the Recycle Filtration System (RFS), because back contamination of endotoxin (ET) from the dialysate in on-line hemodiafiltration (HDF) is a potential problem when a highly permeable membrane is used.

Methods: When the RFS is used for HDF, some of the purified fluid is pumped by a purified fluid pump to the venous side of the blood circuit, and the remainder is returned to the filtrate side of the hemofilter to be used for diffusion. This circuit enables simultaneous diffusion and filtration through the hemofilter.

Results: 1. The rate of removal of urea nitrogen (UN) increased with either decreased or increased quantity of recycled filtration flow (QRF). The rate of removal of beta-2-microglobulin (β2-MG) decreased as QRF increased, but its clearance and removal rate increased as the quantity of drainage flow increased. 2. No significant change in β2-MG clearance was observed in the filtration unit, even when recycling was continued for 24 h. 3. ET was not detected in the filtration unit, even though its level in the dialysate, which was reconstituted with tap water, was 806.2±105.4 EU/L.

Conclusion: It is possible to regulate filtration using the RFS by giving importance to the elimination of either small molecules or low-molecular-weight proteins.