Cascade plasmapheresis with online membrane regeneration: Laboratory and clinical studies

Abstract

The function of a protein permeable membrane (cellulose diacetate) in a hollow-fiber module was investigated with regard to its application in therapeutic plasmapheresis. The membrane serves as a secondary system element and filters physiological plasma proteins, retaining pathogenic proteins located at the heavy end of the plasma protein spectrum. Membrane fouling, resulting from deposition and immobilisation of some types of protein, is remedied by dilution of the plasma (1:12) and repeated back-flushing of the membrane. The membrane under investigation is anisotropic, and conventional filtration (inside → outside) differs from reverse filtration (outside → inside) both in filtration dynamics and protein sieving. Sieving coefficients for a given protein are substantially lower in whole plasma than in a monospecies solution. This holds for both filtration modes. Therefore, the concept of a “hybrid membrane” [7,8], which implies that both the structure of the membrane and protein—membrane interaction determine functional performance, would seem to be appropriate. Use of the membrane and filtration system in plasmapheresis treatment of patients with familial hypercholesterolemia is described. Retrieval fractions for albumin and IgG, the most important plasma proteins with long effective half-lives, are 50-60% of those with conventional filtration using the XK-60 module (Asahi Medical, Japan)