The hemostatic profile of recombinant activated factor VII. Can low concentrations stop bleeding in off-label indications?
BACKGROUND
High concentrations of recombinant activated factor VII (rFVIIa) can stop bleeding in hemophilic patients. However the rFVIIa dose needed for stopping haemhorrage in off-label indications is unknown. Since thrombin is the main hemostatic agent, this study investigated the effect of rFVIIa and tissue factor (TF) on thrombin generation (TG) in vitro.


METHODS
Lag time (LT), time to peak (TTP), peak TG (PTG), and area under the curve after 35 min (AUCo-35 min) with the calibrated automated thrombography was used to evaluate TG. TG was assayed in platelet-rich plasma (PRP) samples from 29 healthy volunteers under basal conditions and after platelet stimulation with 5.0 mug/ml, 2.6 mug/ml, 0.5 mug/ml, 0.25 mug/ml, and 0.125 mug/ml rFVIIa alone and in normal platelet-poor plasma (PPP) samples from 22 healthy volunteers, rFVIIa in combination with various concentrations of TF (5.0, 2.5, 1.25 and 0.5 pM).


RESULTS
In PRP activated by rFVIIa, there was a statistically significant increase in TG compared to basal values. A significant TF dose-dependent shortening of LT and increased PTG and AUCo-->35 min were obtained in PPP. The addition of rFVIIa increased the effect of TF in shorting the LT and increasing the AUCo-->35 min with no effect on PTG but were independent of rFVIIa concentration.


CONCLUSIONS
Low concentrations of rFVIIa were sufficient to form enough thrombin in normal PRP or in PPP when combined with TF, and suggest low concentrations for normalizing hemostasis in off-label indications.
Altman
Raul
R
Centro de Trombosis de Buenos Aires, Viamonte 2008, 1056 Buenos Aires, Argentina. draltman@arnet.com.ar.
Scazziota
Alejandra
A
de Lourdes Herrera
Maria
M
Gonzalez
Claudio D
CD
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