Thromboelastography (TEG) is a valuable diagnostic tool that assesses blood clotting ability, providing a comprehensive evaluation of the coagulation system and aiding in the identification of abnormalities in blood clotting. This article aims to offer an in-depth understanding of the TEG procedure and the interpretation of its results.
Thromboelastography Technique
The TEG procedure entails introducing citrated blood into a sample cup within the TEG machine. This cup oscillates around a submerged torsion pin connected to a computer. As coagulation transpires, the pin adheres to the clot and starts moving with it. The magnitude of the pin's motion directly correlates to the clot's strength. The computer displays the pin's motion graphically, with the torsion pin remaining motionless until clotting begins. The graph is analyzed, and five key parameters are measured.
R-Time (Reaction Time)
The R-Time phase quantifies the duration required for blood to begin clotting after the introduction of a clotting activator. It reflects the latency period preceding the coagulation cascade's initiation, representing enzymatic activation and thrombin generation. Typically, it takes 5 to 10 minutes to achieve a 2 mm amplitude. An extended R-Time may indicate clotting factor deficiencies or the presence of anticoagulants. In patients experiencing bleeding and prolonged R-Time, fresh frozen plasma is commonly indicated to correct R-Time.
K-Time (Kinetical Time)
The K-Time parameter gauges the duration needed for the clot to reach a specific level of firmness at 20 mm. It reflects the initial clot formation's speed and depends on the accumulation and formation of fibrin links from fibrinogen. The standard value for K-Time is 1-3 minutes. If K-Time is prolonged, it may suggest a low fibrinogen level, warranting consideration for transfusing cryoprecipitates to correct the deficiency.
Alpha-Angle
The Alpha-angle parameter evaluates the slope of the curve generated by the TEG machine during the clot formation process. It reflects the rate at which fibrin cross-linking transpires and indicates the clot's strength. The normal value ranges between 50 and 70 degrees. A reduced angle may imply hypofibrinogenemia and may necessitate the administration of cryoprecipitate.
MA (Maximum Amplitude)
The MA parameter measures the blood clot's strength and firmness, offering insights into the blood's overall clotting ability. The typical range for MA is 55-75 mm. If the MA value is decreased, it may indicate thrombocytopenia or platelet dysfunction. In such instances, platelet transfusion or desmopressin acetate may be recommended as potential treatments.
LY30 (Lysis at 30 Minutes)
The LY30 parameter, or Lysis at 30 minutes, in thromboelastography quantifies the percentage of clot breakdown occurring 30 minutes after reaching the maximum amplitude. This phase provides insights into the clot's ability to resist breakdown and the activity of fibrinolysis. The normal range for LY30 is 0-8%. If LY30 is increased, it may suggest heightened fibrinolysis. In such cases, treatment with tranexamic acid may benefit the patient.
RT 7 minutes, K 5 minutes, alpha angle 60 degrees, MA 28 mm, and LY30 4%. What would you do?
Transfuse platelets
Transfuse FFP
Transfuse cryoprecipitate
Give tranexamic acid
In Conclusion
TEG is an invaluable diagnostic instrument that evaluates blood clotting ability. Gaining a thorough understanding of the TEG procedure and the analysis of its results can help detect abnormalities in the coagulation system, leading to effective diagnosis and treatment of bleeding disorders.
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