Assessing the Methodology for Calculating Platelet Contribution to Clot Strength (Platelet Component) in Thromboelastometry and Thrombelastography

Abstract

The viscoelastic properties of blood clot have been studied most commonly using thrombelastography (TEG®) and thromboelastometry (ROTEM®). ROTEM®-based bleeding treatment algorithms recommend administering platelets to patients with low EXTEM clot strength (e.g., clot amplitude at 10 minutes [A10] <40 mm) once clot strength of the ROTEM® fibrin-based test (FIBTEM) is corrected. Algorithms based on TEG® typically use a low value of maximum amplitude (e.g., <50 mm) as a trigger for administering platelets. However, this parameter reflects the contributions of various blood components to the clot, including platelets and fibrin/fibrinogen. The platelet component of clot strength may provide a more sensitive indication of platelet deficiency than clot amplitude from a whole blood TEG® or ROTEM® assay. The platelet component of the formed clot is derived from the results of TEG®/ROTEM® tests performed with and without platelet inhibition. In this article, we review the basis for why this calculation should be based on clot elasticity (e.g., the E parameter with TEG® and the CE parameter with ROTEM®) as opposed to clot amplitude (e.g., the A parameter with TEG® or ROTEM®). This is because clot elasticity, unlike clot amplitude, reflects the force with which the blood clot resists rotation within the device, and the relationship between clot amplitude (variable X) and clot elasticity (variable Y) is nonlinear. A specific increment of X (ΔX) will be associated with different increments of Y (ΔY), depending on the initial value of X. When calculated correctly, using clot elasticity data, the platelet component of the clot can provide a valuable insight into platelet deficiency in emergency bleeding.

Rapid and Correct Prediction of Thrombocytopenia and Hypofibrinogenemia with Rotational Thromboelastometry in Cardiac Surgery Reconsidered

“…Recently, Solomon et al published a review article on assessment of platelet attribution to the formed clot using the clot elasticity parameter (CE). 2 They stated that the CE method is superior compared to our method. Therefor, we did a reconsideration of our data and would like to give the readers of the Journal of Cardiothoracic and Vascular Anesthesia a re-appreciation on this matter.…”

“…In figure 1a our original A5 data was recalculated using CE = (100*A5)/(100-A). 2 The CE results at 5 minutes for platelet contribution (CEextem -CEfibtem) were plotted against the platelet counts. Figure 1b is the same plot as figure 1d in our original publication using PLTEM A5 = A5extem -A5fibtem.…”

Sensitivity of Viscoelastic Tests to Platelet Function

“…However, it must be considered that this approach, even if apparently logical, suffers from a certain degree of bias. Shear modulus (or elasticity) is not linearly associated with clot amplitude, being rather defined by the equation [16]:…”

A Novel Device for the Evaluation of Hemostatic Function in Critical Care Settings

“…Both channels 3 and 4 use hexadimethrine bromide to neutralize residual heparin. The difference between Clot Stiffness and Fibrinogen Contribution represents the Platelet Contribution to clot stiffness 18,19 . The Quantra test results are summarized in Table 2.…”