Abstract
BackgroundThromboelastography is widely used as a tool to assess the coagulation status of critical‐care patients. It allows observation of changes in the material properties of whole blood brought about by clot formation and clot lysis. However, contact activation of the coagulation cascade at surfaces of thromboelastographic systems leads to inherent variability and unreliability in predicting bleeding or thrombosis risks, while also requiring large sample volumes. ObjectivesTo develop a non‐contact drop oscillation rheometry (DOR) method to measure the viscoelastic properties of blood clots and to compare the results with current laboratory standard measurements. MethodsDrops of human blood and plasma (5‐10 μL) were acoustically levitated. Acoustic field modulation induced drop shape oscillations, and the viscoelastic properties of the sample were calculated by measuring the resonance frequency and damping ratio. ResultsDOR showed sensitivity to coagulation parameters. An increase in platelet count resulted in an increase in the maximum clot stiffness. An increase in the calcium ion level enhanced the coagulation rate prior to saturation. An increase in hematocrit resulted in a higher rate of clot formation and increased clot stiffness. Comparison of the results with those obtained with thromboelastography showed that coagulation started sooner with DOR, but with a lower rate and lower maximum stiffness. ConclusionsDOR can be used as a monitoring tool to assess blood coagulation status. The advantages of small sample size, the lack of contact and small strain (linear viscoelasticity) makes this technique unique for real‐time monitoring of blood coagulation.
Highlights
Coagulation monitoring plays a key role in the management of coagulopathic diseases
Drop oscillation rheometry can be used as a monitoring tool to assess blood coagulation status
Traditional approaches include induction of in vitro clotting of plasma (PT, aPTT, fibrinogen) [1], functional assays based on the use of chromogenic substrates (Anti-Xa assays) [2], and studies of platelet function and count [1][3]
Summary
Coagulation monitoring plays a key role in the management of coagulopathic diseases. In the late 1940s, Hartert introduced thromboelastography (TEG) [4,5] to provide a time-dependent assessment of whole blood coagulation. The device, virtually unchanged from its original inception in 1948, measures the torsional motion of a cylindrical pin immersed in blood. The blood is contained in a cup forced to execute oscillatory rotations of roughly ±5° [6]. As the blood clots the rotational motion of the cup is transmitted to the pin, causing it to undergo torsional oscillations as well. TEG’s sensitivity to hypo- and hyper-coagulation defects associated with acute and chronic illness and surgery explains its longevity as a standard diagnostic tool in hospital laboratories [7]
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