Enhanced thrombin generation in plasma of severe thrombocytopenic patients due to rFVIIa

Summary

RFVIIa-enhanced thrombin generation has been shown to be dependent on platelets. In previous work we have shown that addition of monocytes and rFVIIa to microparticle free plasma causes a distinct thrombin generation. The aim of our study has been to examine whether there is enough surface provided by microparticles in thrombocytopenic plasma to allow an effect of rFVIIa. Patients, methods: Thrombin generation was measured in platelet rich plasma (PRP) and microparticle free plasma (MFP) of thrombocytopenic haemato-oncological patients with and without addition of rVIIa by means of calibrated automated thrombography. Microparticles were analyzed in PRP by FACS flow cytometry. Results: Microparticle free plasma showed no thrombin generation with or without addition of rFVIIa. Addition of rFVIIa to PRP of thrombocytopenic patients led to a significant shortening of lag time and time to peak in thrombin generation, while ETP and peak remained unchanged. Conclusion: Our results show that even in plasma of severe thrombocytopenic patients enough surface may be provided by microparticles to allow an enhancement of thrombin generation by rFVIIa.

Zusammenfassung

Einige Studien zeigten, dass für den Effekt von rFVIIa auf die Thrombingeneration Plättchen von großer Bedeutung sind. Ergebnisse unserer Arbeitsgruppe zeigten, dass schon Monozyten in Mikropartikel-freiem Plasma Ursache für eine deutliche Thrombingeneration darstellen. Das Ziel dieser Studie war, zu untersuchen, ob in thrombozytopenischem Plasma genug Phospholipidoberfläche in Form von Mikropartikeln enthalten ist, um einen Effekt von rFVIIa zuzulassen. Patienten, Methode: Die Thrombingeneration wurde in vitro mithilfe der Calibrated Automated Thrombography in Mikropartikel-freiem Plasma (MFP) als auch Plättchen-reichem Plasma (PRP) hämatoonkologischer Patienten mit ausgeprägter Thrombozytopenie mit und ohne Zugabe von rFVIIa gemessen. Die FACS-Durchflusszytometrie wurde zur Darstellung der Mikropartikel in PRP verwendet. Ergebnisse: In MFP kam es mit oder ohne rFVIIa zu keiner Thrombingeneration. In thrombopenischem PRP führte der Einfluss von rFVIIa zu einer signifikanten Verkürzung von Lag-Phase und Time-to-Peak, während ETP und Peak unverändert blieben. Schlussfolgerung: Unsere in vitro-Resultate unterstützen die Annahme, dass die Gabe von rVIIa auch bei Thrombozytopenie sinnvoll sein kann.

Keywords

Thrombin generation - rFVIIa - thrombocytopenia - microparticles

Schlüsselwörter

Thrombingeneration - rFVIIa - Thrombozytopenie

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