Mass Transfer in Membrane Plasma Exchange

Abstract

In vitro and in vivo sieving coefficients (SC) have been determined for a spectrum of proteins ranging in molecular weight from 66,500 daltons (albumin) to 2.4 million (beta-lipoprotein) daltons for three commercially available membrane plasma separation devices: the Plasmaflo 0.1, Plasmaflo 02, and Plasmaflux. A model relating serum level of a protein to pretherapy level, plasma volume, plasma filtration rate, membrane SC, and duration of treatment has been used to investigate the influence of SC on exchange efficiency. Comparison of predicted and clinically obtained reductions in serum solute levels demonstrated the validity of the model. The results of the analysis suggest that all three plasma separators are capable of delivering equally acceptable therapy. The model further demonstrates the decreasing effectiveness, and increased cost in terms of replacement fluid per unit of solute removed, with prolonged treatment times.

Comparative Evaluation of Filters Used in Membrane Plasmapheresis

“…The sieving coefficients for all devices are essentially equivalent, except perhaps for the slightly lower values (0.80-0.90) found for larger permeants with the Plasmaflo AP-05-H. The in vivo sieving coefficients reported here for the Plasmaflux P2 are slightly higher than those first reported by our group [20]; this is most likely a consequence of improved hydrophilization tech niques in more recent production charges.…”

“…The literature does contain reports on the performance of particular filters and some comparisons [19][20][21][22], but there has been no attempt to standardize methodology or to precisely define the various parameters cited. Moreover, there is no rigorous treatment of the criteria for evaluation of sec ondary filters employed to fractionate plasma.…”