Thromboelastography

Thromboelastography (TEG®) is a method of testing the efficiency of coagulation in the blood. It was first developed by Dr. Hellmut Hartert in 1948. It is especially important in surgery and anesthesiology.

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The original method

In classical thromboelastography, a small sample of blood (typically 0.36 ml) is placed into a cuvette (cup) which is rotated gently through 4º 45´ (cycle time 6/min) to imitate sluggish venous flow and activate coagulation. When a sensor shaft is inserted into the sample a clot forms between the cup and the sensor. The speed and strength of clot formation is measured in various ways (now usually by computer), and depends on the activity of the plasmatic coagulation system, platelet function, fibrinolysis and other factors which can be affected by illness, environment and medications.

The patterns of changes in strength and elasticity in the clot provides information about how well the blood can perform hemostasis (the halting of blood flow), and how well or poorly different factors are contributing clot formation.

Other methods

Rotation thromboelastography or ROTEM (the name is a trademark of Pentapharm) is another version in which it is the sensor shaft rather than the cup which rotates. The shaft typically rotates back and forth 4º 45´ (cycle time 10/min). It is connected with a spring to measure elasticity. As the blood in the cuvette begins to clot there is a loss of elasticity in the spring causing changes in the rotation of the shaft. These changes are detected by the light reflected by the small mirror on the shaft and are converted by a transducer to electrical signals which are then measured by a computer.

Pentapharm claims this opto-mechanical detection method makes this method more precise and less vulnerable to vibration and mechanical shocks than the classical method making the transportation and installation of the instrument very simple.

References

• Wenker, Olivier C.; Wojciechowski, Zbigniew; Sheinbaum, Roy; Zisman, Eli. "Thrombelastography". The Internet Journal of Anesthesiology. 2000. Volume 1 Number 3.
• Whitten, Charles W. M.D.; Greilich, Philip E. M.D. "Thromboelastography: Past, Present, and Future". Anesthesiology. 92(5):1226, May 2000.
• Pentapharm GMBH: Thromboelastography
• Free simulation of a thromboelastograph (Requires Registration)