Thromboelastography (TEG®) is a point-of-care testing method that provides a comprehensive analysis of a patient's hemostatic system including fibrinolysis. TEG® provides crucial information to guide transfusion and hemostatic therapy in complex cases. This article will discuss what TEG® is, how it works, its clinical applications and the benefits it provides over standard coagulation tests.

What is Thromboelastography?

Thromboelastography was developed in the 1940s by Dr. H. Hartert as a method to continuously monitor the coagulation process over time. TEG® analyzes the viscoelastic properties of whole blood coagulation under low-shear conditions. A small amount of whole blood is placed in a cylindrical cup housed within the TEG® analyzer. A pin suspended from the center of the cup is oscillated by a pendulum-like motion. As the blood clots, fibrin strands form between the cup and the pin, transmitting the rotational forces throughout the developing clot. This allows TEG® to continuously monitor clot formation, clot strength, fibrinolysis and lysis.

How TEG® Works

When blood is placed in the cup, coagulation is initiated with the addition of a physiological activator such as tissue factor or ellagic acid. As coagulation is activated, the TEG® analyzer measures changes in the viscoelastic properties of the clot over time. These changes are detected by the motion of the pin suspended in the cup and converted into an output tracing called a thromboelastograph. The tracing provides information on five key parameters:

- Reaction Time (R): Latency between activation and clot formation

- Kinetics (K): Speed of clot buildup

- Angle (α): Rate of clot strengthening

- Maximum Amplitude (MA): Ultimate clot strength

- Lysis 30 (LY30): Extent of fibrinolysis after 30 minutes

Clinical Applications of TEG

Transfusion Guidance: TEG® allows for goal-directed use of blood products and fibrinogen concentrates. It can detect deficiencies the may warrant administration of platelets, plasma or cryoprecipitate.

Trauma and Surgery: TEG® is useful for managing coagulopathic bleeding in complex trauma, liver transplantation, cardiac surgery and other cases. It detects coagulopathies and guides hemostatic therapy.

Perioperative Monitoring: TEG® provides continual monitoring of coagulation during prolonged surgeries. It allows for early detection of consumption coagulopathy and guides appropriate therapy.

Obstetrics: TEG® is beneficial in cases of obstetric hemorrhage, placental abruption or amniotic fluid embolism by guiding therapy to reverse coagulopathies.

Inherited Bleeding Disorders: TEG® enhances management of bleeding episodes in hemophilia, von Willebrand disease and other rare bleeding disorders.

Benefits over Standard Tests

Comprehensiveness: TEG® provides a global assessment of hemostasis including fibrinogen function, platelet contribution and fibrinolysis; standard tests only assess isolated aspects of coagulation.

Rapidity: TEG® results are available within 10 minutes whereas standard tests often take 30-60 minutes. This allows for earlier intervention.

Physiologic activator: TEG® uses whole blood and a physiological activator allowing for a true assessment of in vivo hemostasis; standard tests use plasma and artificial activators.

Monitoring ability: TEG® provides continuous monitoring of coagulation over time allowing the detection of developing coagulopathies; standard tests provide single time point data.

Targeted therapy guidance: The bedside availability and comprehensive results of TEG® allow for directed goal-based transfusion of specific clotting factors or inhibitors of fibrinolysis.

In summary, thromboelastography provides an invaluable whole blood assessment of hemostasis that guides targeted treatment of coagulopathy. Its rapidity, monitoring ability, and ability to detect deficiencies tailors therapy and improves bleeding outcomes in complex clinical situations. As its use expands, TEG® will continue enhancing transfusion practice and management of bleeding disorders.

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