Coagulation, hemostasis, and plasma expanders:a quarter century enigma.

Despite more than 2 decades of research, the explanation of the long-known hemostatic failure consequent to the use of some natural and synthetic macromolecular agents as plasma substitutes remains obscure. Conventional clotting parameters are not significantly affected in vivo or in vitro. Dextran, hydroxyethyl starch, and many other colloid macromolecules precipitate Factors I and VIII, fibrin monomer, and perhaps v. W. (von Willebrand) factor(s) from plasma, rendering at least the first three insoluble, in relation to the molecule size and concentration of the colloid, and for dextran, its intrinsic viscosity. The precipitate, rich in Factors VIII and I, redissolves on warming, and reprecipitates on cooling, behaving as a cryo-Factor I. In composition it closely resembles the cryoprecipitate obtained by slow-thawing of plasma. Both clot faster with thrombin than the parent plasma. The amount precipitated from plasma by dextran or hydroxyethyl starch varies very widely from individual to individual. Cryo- of dextran-precipitable material can be obtained by interacting purified Factor I with a miniscule amount of thrombin. Dextran, hydroxyethyl starch, polyvinyl pyrrolidone, some forms of gelatin, and several polyamino acids accelerate thrombin clotting of normal plasma, several dysfibrinogenemic plasmas, or Factor I. Albumin, hemoglobin, some modified gelatins do not. Poor platelet thromboplastic function appears some hours after dextran infusion, associated with morphologic capillary abnormalities that strikingly resemble those in v. W. disease. We postulate that the hemostatic defect associated with the use of plasma substitutes is a form of induced v. W. disease or disseminated intravascular clotting, ensuing from precipitation and removal of v. W. factor(s), Factors VIII and I, microcirculatory abnormality, and platelet malfunction. The latter two supervene some time after administration of dextran. It reported antithrombotic activity is perhaps referable to the same action.