Studies on Increased Heparin Resistance Measured by the Plasma Heparin Thrombin Time

Abstract

Increased heparin resistance was found to remain unchanged in BaSO₄-adsorbed plasma, but disappeared following adsorption with large quantities of Al(OH)₃. The factor V content in the plasma could be considerably reduced without any alteration in the heparin resistance. Antihaemophilic globulin exerted no influence upon the heparin thrombin time. Tissue thromboplastin in quantities sufficient to accelerate the clotting of recalcified plasma considerably, did not affect the heparin thrombin time. Plasma thromboplastin had no antiheparin effect. Increased heparin resistance was — although usually less marked — still demonstrable in most cases in plasma defibrinated with thrombin from patients with a greatly shortened heparin thrombin time, but not in cases of less pronounced shortening. Fibrinogen prepared by the freeze-thaw technique from normal plasma and patient plasma showed no difference in reactivity to heparin and thrombin. In experiments on plasma mixtures, a shortening of the heparin thrombin time was still demonstrable at the ratio 9 parts of normal plasma to 1 part of plasma from patients with greatly increased heparin resistance. The antithrombin content of plasma was not reduced in increased heparin resistance. ^* Aided by grants from Arvid Nilsson’s Foundation, Copenhagen, Denmark.