Dialysis membranes and coagulation system.

Artificial membranes used for hemodialysis differ from endogenous membranes, i.e. endothelial cells, by their variable thrombogenicity. The key step in activation of the coagulation system by dialysis membranes is thrombocyte activation which is preceded by formation of a protein layer of critical thickness. Crucial questions concerning the quality of this protein membrane as a determinant of thrombocyte activation are not well understood. Activation of the contact phase of the intrinsic plasmatic coagulation system by dialysis membranes is well documented. Local action of thrombin in the membrane microenvironment is documented by release of fibrinopeptide A and deposition of fibrin on the membrane. Apart from thrombin, other mechanisms, e.g. PMN elastase, plasma-independent activation of blood cells, facilitatory action of erythrocytes etc., may play a contributory role. With respect to the polycarbonate membrane, some authors find less platelet extraction and unchanged platelet release reaction. In our own studies, polycarbonate membranes were not superior to cuprophane membranes with respect to thrombogenicity.