Quantification of Device Adherent, Circulating, and Organ Pool of Thrombin and Fibrinogen After Cardiopulmonary Bypass in a Pig Model

The pool of thrombin and fibrinogen in circulation, in organs, and on cardiopulmonary bypass devices was quantified during and after cardiopulmonary bypass in four groups of 24 Yorkshire pigs (weight, 30–35 kg); two groups of 10 unoperated pigs were used as controls. Thrombin-α and fibrinogen were iodinated with iodide using an iodogen transfer technique; 250–300 µCi of these tracers were injected intravenously 1 hr before cardiopulmonary bypass. All pigs were systematically heparinized (activated clotting time > 400 sec); cardiopulmonary bypass was performed at 2.5–3.5 L/min at 28°C using a centrifugal pump, oxygenator (Bentley Univox 1.8 m; Bentley Inc., Irvine, CA), arterial filter (0.25 m), and cardiotomy reservoir (BMR 3500) for 90 min, followed by a 90 min reperfusion and 180 min of cardiopulmonary bypass. Iodinated thrombin-α and fibrinogen in intact organs and samples of blood, organs, tissues, and oxygenator-arterial filter-cardiotomy reservoir were quantified with an ion chamber and a gamma counter, respectively. The percent of injected iodinated thrombin-α and fibrinogen dose (mean ± SD) in organs and cardiopulmonary bypass devices of all groups of cardiopulmonary bypass pigs was calculated. Thrombin generated at the small area of surgical wounds (0.016–0.038 m), and fibrin deposited on surfaces of cardiopulmonary bypass devices (2.59 m), initiate and propagate thrombus formation and embolization. The protein level reached saturation values on all cardiopulmonary bypass devices at 180 min. High levels of thrombin and fibrinogenfibrin circulate in blood and organs, and are adsorbed on cardiopulmonary bypass devices; this large blood pool of procoagulants in the cardiac cradle, tissues, and perfused organs may account for thrombi and emboli during and after cardiopulmonary bypass.