Extracorporeal Thrombogenesis: Mechanisms and Prevention

The exposure of blood to artificial surfaces either extracorporeally or intracorporeally initiates a number of diverse reactions (1–4). Immediately following the exposure of most artificial surfaces to blood, various plasma proteins begin to adsorb to those surfaces. The interaction of plasma proteins with artificial surfaces can initiate the activation of the intrinsic and extrinsic blood coagulation, the kinin, the complement, and the fibrinolytic systems. Ultimately, thrombin may be formed, and this enzyme may adhere to artificial surfaces in an active state. While various proteins are adsorbing to an artificial surface and establishing an equilibrium state, blood cells begin to adhere to the adsorbed protein layer. Erythrocytes seem to adhere poorly to such a surface, but platelets and leukocytes, especially neutrophils, are attracted to the adsorbed protein layer, frequently in large numbers. Adhesion of leukocytes to the artificial surface may lead to activation of the extrinsic blood coagulation system through the exposure of tissue factor on the plasma membranes of the adherent cells.