RESUMO
The effect of blood contact and reprocessing using bleach on the convective transport of both neutral and positively charged dextrans was determined for cellulose triacetate (CT), polyacrylonitrile (PAN), and polysulfone (PS) dialyzers (Fresenius USA, F60B, Concord, CA). For neutral dextrans, blood contact reduced the convective permeability, determined by differences in the sieving coefficient profile for both the PAN and PS, but not for CT dialyzers. Reprocessing of the dialyzers with bleach (up to 15 reuses) did not affect the convective transport of dextrans through CT or PAN, but did enhance the permeability of the blood contacted PS dialyzers. However, sieving coefficients for the blood contacted and reprocessed PS (F60B) dialyzers were significantly lower than those for the other dialyzers studied, approaching zero for dextrans larger than 18 k molecular weight. Sieving coefficients for positively charged, diethylaminoethyl (DEAE) dextrans were a function not only of solute size, but also of the membrane's capacity for adsorption of charged molecules. The majority of smaller, filtered DEAE dextrans adsorbed to the PAN membrane. Adsorption of DEAE dextrans to PAN was not observed for larger dextrans, or for DEAE dextrans of any size with CT, despite the lower permeability of both membranes for DEAE dextran compared to that for neutral dextrans.