Heparin is associated with adverse effects in some patients during extracorporeal circulation. A potential alternate anticoagulation strategy explored in this investigation involved mitigation of coagulation by removing clotting factors from blood by adsorption on a protamine-immobilized Sepharose matrix (PSM). Human or porcine plasmas treated with PSM in vitro were tested for clotting factors I (fibrinogen), II (prothrombin), VIII, and X, and proteins C and S, and for prothrombin time (PT), activated partial thromboplastin time (APTT), and total protein concentration. Bovine blood treated with PSM was also perfused through a hollow-fiber cartridge to assess thrombogenic potential in a shear flow system. PT increased with increasing protamine-Sepharose-to-plasma ratios and with increasing mixing time. When the PT and APTT of treated plasma were prolonged three to six times the baseline, Factors II and X were significantly removed (>90%), Factors I and VIII were partly removed (<35%), and total protein concentration remained >80% of the initial value. When blood depleted of clotting factors was perfused through hollow-fiber cartridges without an anticoagulant, cartridge patency was prolonged compared with cartridges perfused with untreated blood. This investigation demonstrated that inhibition of blood coagulation by removal of key clotting proteins is feasible.

A subpopulation of patients would benefit from an anticoagulation strategy during extracorporeal circulation (ECC) that does not involve systemic administration of heparin and protamine. Inhibition of coagulation by adsorption of plasma clotting factors using protamine immobilized on a Sepharose matrix (PSM) has been explored. This investigation extends previous in vitro studies and demonstrates the feasibility of heparin-free ECC. In a porcine ex vivo circuit, plasma was separated from blood via plasmapheresis, passed through a column containing PSM beads, and returned to the animal. Hemodialyzers and stents were placed in the circuit before, during, and after ECC and examined for device thrombosis. After 90 minutes, prothrombin time (PT) was prolonged >10 times the baseline, and blood clotting Factors I, II, VIII, and X were decreased significantly (>90%); this state was maintained for 2.5 hours without detectable adverse consequences. After cessation of ECC, PT approached normal levels within 60 minutes. Examination of hemodialyzers and coronary stents placed in the circuit revealed that the removal of clotting factors significantly reduced device thrombosis and that transfusion of homologous blood ( approximately 10% V/V) resulted in immediate restoration of hemostasis. It is possible to remove clotting factors from circulating blood to allow extracorporeal circulation of blood without the use of heparin.