THE EFFECT OF BLOOD CONTACT AND REUSE ON THE TRANSPORT-PROPERTIES OF HIGH-FLUX DIALYSIS MEMBRANES

The effect of blood contact and reprocessing using bleach on the conve ctive transport of both neutral and positively charged dextrans was de termined for cellulose triacetate (CT), polyacrylonitrile (PAN), and p olysulfone (PS) dialyzers (Fresenius USA, F60B, Concord, CA). Far neut ral dextrans, blood contact reduced the convective permeability, deter mined by differences in the sieving coefficient profile for both the P AN and PS, but not for CT dialyzers. Reprocessing of the dialyzers wit h bleach (up to 15 reuses) did not affect the convective transport of dextrans through CT or PAN, but did enhance the permeability of the bl ood contacted PS dialyzers. However, sieving coefficients for the the blood contacted and reprocessed PS (F60B) dialyzers were significantly lower than those for the other dialyzers studied, approaching zero fo r dextrans larger than 18 k molecular weight. Sieving coefficients for positively char,bed, diethylaminoethyl (DEAE) dextrans were a functio n not only of solute size, but also of the membrane's capacity for ads orption of charged molecules. The majority of smaller, filtered DEAE d extrans adsorbed to the PAN membrane. Adsorption of DEAE dextrans to P AN was not observed for larger dextrans, or for DEAE dextrans of any s ize with CT, despite the lower permeability of both membranes for DEAE dextran compared to that for neutral dextrans.