Hematology: Thrombelastogram (TEG)

Testing

Basics

  • Measures the Viscoelastic Properties of Clot Formation in Real Time
  • Procedure:
    • A Small Cup of Blood is Activated & Rotates Around a Pin
    • A Clot Forms Around the Pin & Parameters are Measured
  • *Does Not Reliably Detect Effects of Commonly Use Anticoagulants
  • Increasingly Being Used in Trauma
    • Conventional Tests Take a Long Time (Over 80 Minutes) and are Often Inaccurate by The Time They Result Due to Transfusions & Physiologic Changes
    • Used to Guide Massive Transfusion & Identify Trauma Induced Coagulopathy
    • May Decrease Transfusion Requirements (Controversial Area of Active Study)
    • *See Hemorrhagic Shock & Trauma Resuscitation

Commercial Types

  • Thrombelastogram (TEG)
    • *Not “Thromboelastogram” – Common Misspelling
  • Rotational Thromboelastography (ROTEM)
    • Similar but Different Nomenclature of Results

Modifications

  • Speed – Based on Activating Agents:
    • Standard TEG – Uses Kaolin (A Type of Clay) to Activate Clot
    • RapidTEG – Uses Kaolin & Tissue Factor to Accelerate Reaction
  • Heparinase
    • Added Heparinase (Enzyme to Neutralize Heparin)
    • Measures Inhibitory Effects of Heparin
  • Functional Fibrinogen
    • Added Cytochalasin D (Alkaloid Produced by Fungus, Inhibits Platelet Activity)
    • New Maximum Amplitude Differentiates Deficiencies in Fibrinogen vs Platelets
  • Platelet Mapping
    • Added Adenosine Diphosphate (ADP) & Arachidonic Acid
    • Measures Inhibitory Effects of Antiplatelet Agents (Aspiring/Clopidogrel)

Result Interpretation

Reaction Time (R Time)/Activated Clotting Time (ACT)

  • Measures: Time to Initiate Clot Formation
  • Normal:
    • R Time (Normal TEG): 5-10 Minutes
    • ACT (RapidTEG): 80-140 Seconds
  • Prolonged: Issue with Coagulation Factors
    • Treatment: FFP

K Time

  • Measures: Time to Reach a Fixed Strength
  • Normal: 1-3 Minutes
  • Prolonged: Issue with Fibrinogen
    • Treatment: Cryoprecipitate

α Angle

  • Measures: Speed of Growth
  • Normal: 53-72 Degrees
  • Low: Issue with Fibrinogen
    • Treatment: Cryoprecipitate

Maximum Amplitude (MA)

  • Measures: Highest Vertical Amplitude
  • Normal: 50-70 mm
  • Low: Primarily an Issue with Platelets, Fibrinogen May Contribute
    • Treatment: DDAVP/Platelets & May Consider Cryoprecipitate

Lysis at 30 Minutes (LY30)

  • Measures: Percentage of Clot Amplitude Reduction 30 Minutes After the Maximum
  • Normal: 0-3%
  • High: Excess Fibrinolysis
    • Treatment: TXA