Blood purification by a membrane technique--a new method for the effective removal of low-density lipoprotein cholesterol.

A membrane plasma fractionation (MPS) technique is applied in order to obtain selective removal of pathological plasma components from the extracorporeal circuit. An effective plasma fractionation procedure should be characterized by the highest possible removal of the pathological plasma components and, equally as important, the lowest unwanted protein losses caused mainly by adsorption to the membrane structure. In order to obtain a higher efficiency of the MPS procedure (high selectivity between removal of pathological plasma components and unwanted losses mainly represented by albumin) several methods such as thermofiltration, application of pulsate flow at the end of secondary filter, etc. have been developed. Clinical verification of these methods led to some improvement in MPS procedure but these results did not seem to be optimal. The main objective of this paper is to present a new two-stage membrane system utilizing a high flow recirculation circuit developed particularly, but not only, for effective removal of low-density lipoprotein cholesterol. The designed and developed system has been tested in vitro using several different plasma fractionation membranes. The results obtained indicated the importance of the membrane structure and membrane material on the efficiency of the tested plasma fractionation procedure. It was also found that it is possible to obtain negligible protein losses for some selected membrane structures applied in the assessed system. Based on preliminary results, it seems that the new two-stage membrane system proposed could be characterized by a very low range of unwanted protein losses leading to high effectiveness of the plasma fractionation procedure.