Thromboelastometry

Thrombelastography Thromb or ( o) is a diagnostic elastometrie ( viscoelastic ) method, with the clotting properties ( hemostasis ) can be examined by whole blood. In contrast to the conventional coagulation analyzes ( Quick, aPTT) the strength of the clot with a resolution and various special issues can be detected.

Development

1948 was described by Hartert in Heidelberg, the principle of thrombelastography. Due to the sophisticated handling and vibration sensitivity of these "classical thromboelastography " it could hardly prevail in everyday clinical practice, however, took place in America a certain distribution (TEG ®, Haemoscope, USA).

Later emerged as the development Resonanzthrombographie (RTG 801, 1977, Fresenius Medical Bad Homburg and ROM Orbitometer 4, 1988, Amelung Lemgo ). This method was carried out in some centers haemostaseological, but could not permanently established in the clinical application itself.

In the early 1990s, the principle of rotation elastography ( ROTEG ) was developed, which is insensitive to vibrations and thus point- of-care capability substantially. From name for legal reasons later was renamed to Rotationsthromboelastometrie ( ROTEM ®, Tem Innovations GmbH, Munich).

Method

In classical thrombelastography forms on a stamp, which projects into a pivoting longitudinally sample vessel with the blood sample, the blood clot. With increasing clotting the movement is transmitted to the stamp, which can be plotted as a curve over time. When Rotationsthromboelastometrie the other hand, the punch rotates with a fixed vessel. The measurement approach is performed with citrated blood, clotting is initiated by the addition of calcium and activators.

There are various commercial ROTEM ® systems available that allow different differential diagnostic statements. With INTEM ( contact activation ) is preferable to the intrinsic pathway, with EXTEM (activator: Tissue factor) tested the extrinsic pathway of blood coagulation. HEPTEM can identify the effect of heparin ( added heparinase ). FIBTEM can plasmatic fraction from platelet proportion of coagulation differ ( addition of cytochalasin D). APTEM, the presence of a strong Hyperfibrinolysis show ( same inhibition by aprotinin ). For TEG ® is a heparinase test exists ( heparin influence) and a kaolin -activated test ( intrinsic system ).

Interpretation

The clotting time or coagulation time (CT, RED ) and the r-value (TEG ), the latency from the time of addition of the activator until the onset of clot formation. It corresponds to the Quick value ( EXTEM ) and aPTT ( INTEM ). A prolongation of the clotting time, by coagulation disorders are mainly caused by a lack of clotting factors or heparin (depending on the test). A heparin effect by comparing the clotting time of INTEM tests to determine the clotting time of HEPTEM tests.

As clotting formation Time ( CFT, RED ), or K- value defines the time from the onset of clot formation, until an amplitude of 20 mm. This value provides an indication of the speed of the clot formation.

The clot strength is measured by the maximum clot firmness ( MCF, RED ) and maximum amplitude (TEG ). Lysis index ( LI) is the decrease in 60 minutes after clot formation and displays the fibrinolysis. He is < 85 %, there is a hyperfibrinolysis. In massive hyperfibrinolysis clotting can be completely removed, then the APTEM approach allow clotting and distinguish it from a fibrinogen deficiency.

Areas of application

Areas of application are unclear bleeding during surgery or trauma, suspicion of hyperfibrinolysis, monitoring of fibrinogen substitution, and thrombocytopenia. A reduction in blood therapy costs by thromboelastometry in cardiac surgery has been shown, also treatment decisions in the emergency room quickly erfolgen.Für the measurement of fibrinolysis, the TEM is considered the gold standard for which there is no equivalent laboratory parameters.

Limitations

The thromboelastometry takes place in an artificial system that is not an exact representation of the physiological coagulation conditions. Thus, the flow behavior in the vascular system remains largely ignored. Disorders of primary hemostasis ( von Willebrand syndrome), pharmacological effects of acetylsalicylic acid (ASA ) and ADP antagonists such as clopidogrel are not recognized glycoprotein IIb or Glanzmann 's disease is limited. The EXTEM value correlates poorly with the Quick value. The coagulation inhibitors potential ( antithrombin, protein C, protein S) is also recorded poorly. Controlled studies that show a reduction in mortality, are not available.