ROLE OF FACTOR-XII IN THROMBIN GENERATION AND FIBRINOLYSIS DURING CARDIOPULMONARY BYPASS

During cardiopulmonary bypass, thrombin is generated, which is thought to be initiated by activation of factor XII on the surface of the bypass equipment. We present a patient with severe factor XII deficiency who underwent cardiac surgery. As much thrombin was formed during cardiopulmonary bypass (measured by the prothrombin activation fragment F-1+2 and thrombin-antithrombin complexes) as in normal patients, showing that factor XII was not necessary for thrombin generation. Factor X, but not factor IX, was activated (as measured by their activation peptides), and this activation correlated with F-1+2 and thrombin-antithrombin complexes, suggesting that the tissue-factor/factor-VIIa pathway is the trigger for thrombin formation.