The role of platelets in blood coagulation—effects of platelet agonists and GPIIb/IIIa inhibitors studied by free oscillation rheometry

Abstract

We have studied the contribution of platelets to the coagulation of plasma and the effects of activation or inhibition of platelets on the coagulation process in unanticoagulated fresh whole blood (subsequently termed native blood). For this purpose we have used a free oscillating rheometer (FOR), the ReoRox4  , a new instrument enabling non-invasive viscoelastic measurements of clot formation in plasma and whole blood.Platelets appear essential for the initiation of coagulation if no activating surface is present. We prepared platelet-free plasma by quick centrifugation and filtration of native blood, which did not coagulate if stored in plastic containers at 37C but clotted if transferred to glass containers. To our knowledge, this is the first report showing that activation of platelets in native whole blood shortens the coagulation time ex vivo. It also describes a new instrument, enabling studies of the viscoelastic properties of a forming whole blood clot.

Clotting time analysis of citrated blood samples is strongly affected by the tube used for blood sampling

“…Further studies are needed to answer that question. From our point of view, however, the Monovette system seems to be preferable, since the clotting times recorded with these tubes are similar to the ones we usually obtain from blood without any anticoagulant added [10]. Wolf P. The nature and significance of platelet products in human plasma.…”

“…The presence of activated platelets has previously been shown to shorten the clotting times [10]. The same shortening might possibly occur if the plasma contains microparticles released from platelets, since these have been shown to support coagulation via tissue factor-independent pathways [11].…”

Calibrated Automated Thrombin Generation Measurement in Clotting Plasma

“…Several methods exist that measure the moment of clot formation and ensuing changes in the mechanical or optical properties of the clot and/or retraction of that clot through activated platelets, such as thrombelastography [47], resonance thrombography: [48], roTEG coagulation analysis [49], the sonoclot analyzer [50], measurement of platelet-mediated force development during clot formation [51] and free oscillation rheometry [52]. The results of such methods sometimes show a superficial similarity to thrombin generation curves [53].…”

Onset of force development as a marker of thrombin generation in whole blood: the thrombin generation time (TGT)

“…The onset of clotting can be detected and therefore should correlate with the onset of thrombin production. A much more quantitative approach is offered by the ReoRox ® (MediRox, Linkoping, Sweden), which measures shear modulus, loss modulus, phase angle, damping and frequency of a sample held between an oscillating outer cup and an inner probe [40]. Onset of clotting and clot completion time are measured as well as the elastic properties of the resultant clot.…”