Membrane cascade plasmapheresis: theoretical analysis and in vitro studies.

As the donor plasma required in plasmapheresis therapy is not only expensive but may also cause side effects and transfer of infections, attempt was made in the present work to generate continuously autologous purified plasma. A membrane cascade plasmapheresis (MCP) system was developed which: 1. Separates plasma from blood using a membrane plasma separator 2. Fractionates this plasma into two fractions using a secondary filter, one fraction rich in albumin and the other rich in immunoglobulins 3. Returns to the patient filtered blood combined with albumin-rich plasma fraction Ringer solution was used to compensate for the loss of plasma volume rejected as immunoglobulins. The main problem is to maximize the clearance of IgG and recovery of albumin. Theoretical analysis of the system shows that the clearance of IgG increases with the increase in Ringer solution flow rate. However, this increase in clearance of IgG is accompanied by a decrease in albumin recovery. Theoretical analysis presents a relationship between the clearance of protein as a function of their sieving coefficients of the secondary filter, plasma separation rate, and the priming volume. In vitro evaluation of the system using patient's plasma and a Kuraray 2A filter (secondary filter) show that the relative clearances of IgG and albumin lie in the range of 65-70% and 40-45%, respectively. Further improvement in the selectivity of the secondary filter is necessary to minimize the clearance of albumin and to increase the clearance of IgG.