A case of Glanzmann's thrombasthenia successfully treated with recombinant factor viia during a surgical procedure: observations on the monitoring and the mechanism of action of this drug.

Recombinant factor VIIa (rFVIIa) has been shown to be efficient for the treatment of haemorrhages in patients with Glanzmann's thrombasthenia presenting anti-glycoprotein IIb-IIIa antibodies, but the mechanism of action is not well established and there is no routine laboratory test for the monitoring of rFVIIa. In this study, thrombin generation (TG) test was used to assess the efficacy of rFVIIa ex vivo in a Glanzmann patient with inhibitor, who had a surgery for cholesteatoma. The day before surgery, TG capacity in platelet rich plasma was significantly diminished (Endogenous thrombin potential = 637nM x min) in comparison with the normal control group (1338+/-353 nM x min). Thirty minutes after the first infusion of 90 microg/kg of rFVIIa, TG was increased by 59% (1010 nM x min). rFVIIa was administered as intravenous bolus injection of 90 microg/kg q x 2h during the first 24h, than 66microg/kg q x 2h during 24h and 53 microg/kg q x 2h on the post-operative day 3. Residual TG capacity measured before rFVIIa administration mostly remained above 1000nM x min and the coagulation capacity was not significantly modified after a new injection of rFVIIa. The fibrin network was studied with 3D confocal microscopy using clots obtained with TG test. After rFVIIa infusion, the fibrin network was tighter in comparison with the sample before rFVIIa injection. These results provide further ex vivo evidence on haemostatic efficacy of rFVIIa in Glanzmann's patients.