Activation of platelets in whole blood by recombinant factor VIIa by a thrombin-dependent mechanism.

Recombinant factor VIIa (Novoseven) is now proven to be an effective hemostatic agent in hemophiliac patients with inhibitors, as well as in uncontrolled bleeding in surgical and trauma non-hemophiliac patients. However, the exact mechanism of its action is still not well understood, especially regarding its role in platelet activation, and its requirement for tissue factor, thrombin and other coagulation factors.

This is a very elegant paper which looked at the effect of high concentration of rFVIIa on platelet activation, and its interaction with several factors such as calcium, thrombin and white cells. Platelet activation was shown to be thrombin and calcium dependent, but XII involvement was not necessary. This activation may be independent of tissue factor at high concentration of rFVIIa.

– Maadh Aldouri