The role of platelets and recombinant factor VIIa on thrombin generation, platelet activation and clot formation.

In the present study we assessed the effect of platelet counts and rFVIIa on thrombin generation, platelet activation and clot formation after tissue factor pathway activation in human plasma aiming to investigate the mechanism by which rFVIIa induces haemostasis in patients with severe thrombocytopenia. Plasma samples with platelet counts from 5 x 10(9)/l to 150 x 10(9)/l were spiked with rFVIIa (1 micro g/ml) or buffer. Clotting was initiated in the presence of diluted thromboplastin.

On the mechanism of inhibition of tissue factor pathway by the synthetic pentasaccharide during coagulation of human plasma.

The tissue factor (TF) pathway is preponderant in the initiation of blood coagulation in normal haemostasis and in thrombotic states. In the present study we investigated the mechanisms by which the synthetic pentasaccharide may influence the regulation of the TF pathway during clotting of human platelet poor plasma (PPP). Clotting of normal PPP or plasmas immuno-depleted of a single clotting factor (factor VII, factor XII, factor XI, factor IX, factor VIII, factor X, factor V, factor II) was initiated by triggering the TF pathway in the presence of fondaparinux (0.

Inhibition of factor VIIa generation and prothrombin activation by treatment with enoxaparin in patients with unstable angina.

Factor VIIa (FVIIa) and thrombin generation occur in patients suffering an acute coronary event. We studied the effect of treatment with enoxaparin on FVIIa and prothrombin activation in patients with unstable angina. Anti-Xa activity, FVIIa, FVII coagulant activity (FVII:C) and FVII antigen (FVII:Ag), free tissue factor pathway inhibitor (TFPI), and prothrombin fragments 1 + 2 (F1+2) were measured in patients' plasma, over a 24-h treatment period with enoxaparin.

On the mechanism of action of recombinant activated factor VII administered to patients with severe thrombocytopenia and life-threatening haemorrhage: focus on prothrombin activation.

We report the ex vivo effect of recombinant activated factor VII (rFVIIa) on prothrombin activation after whole blood clotting. Two patients with severe thrombocytopenia and life-threatening haemorrhage were successfully managed using a single dose of rFVIIa (90 microg/kg). Western blotting using antiprothrombin antibody showed that rFVIIa did not induce thrombin generation in citrated platelet-poor plasma.