Fondaparinux is a new anticoagulant that interacts with antithrombin III and activated coagulation factor X resulting in an inhibition of the coagulation system. It has been successful in doses of 2.5 mg for thromboprophylaxis as well as in higher therapeutic doses of 5- 7.5 mg. No optimal method for monitoring the effects of fondaparinux has been proposed. The aim of the present study was to investigate whether a viscoelastic coagulation analyzer, the Sonoclot (Sienco, Denv er, Colorado, USA), could be used for in-
vitro monitoring of fondaparinux.
Different concentrations of fondaparinux were added in-vitro to whole blood taken from eight volunteers. The blood samples mixed with the
various amounts of fondaparinux were analyzed using the Sonoclot. The whole- blood
activated partial thromboplastin time with the Hemochron Jr (IT C, Edison, New Jersey , USA) was used as the reference coagulation analysis. All analyses were started expeditiously , within 30 s from sampling, and were performed at 37°C. The values of the Sonoclot parameter clot rate, which measures the rate of fibrin formation, fibrin
polymerization and platelet- fibrin interactions, were significantly correlated to increasing concentrations of fondaparinux (R = - 0.90).
The Sonoclot parameters of activated coagulation time, time to peak and clot retraction had weaker, but still significant, correlations to fondaparinux concentrations. At prophylactic doses (0.38 µg/ml blood)
the clot rate decreased 15% compared with the initial unanticoagulated value, whereas at therapeutic doses (1 .53 µg/ml blood) there was a 27% decrease.
In conclusion, the Sonoclot parameter clot rate could be of clinical value to individualize the fondaparinux dosage, especially the higher, therapeutic, dosages.
ACT Machine Cardiac surgery Heparin Management LMWH Fondaparinux Monitoring
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