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Targeted Resuscitation with TEG & ROTEM

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Viscoelastic testing, specifically through thromboelastography (TEG) and rotational thromboelastometry (ROTEM), has transformed how clinicians manage life-threatening bleeding in trauma victims. Unlike traditional lab tests that only analyze isolated blood components, these tools provide a real-time, comprehensive view of how whole blood forms and dissolves clots. By offering immediate data on clotting strength and speed, these technologies allow for precision-guided resuscitations that utilize specific blood products rather than generic protocols. Research indicates that using these methods reduces mortality rates and prevents the unnecessary use of transfusions by accurately identifying coagulation abnormalities. Furthermore, these diagnostics help doctors predict secondary risks, such as excessive clot breakdown or the potential for dangerous blood clots after the initial injury. Ultimately, integrating these advanced monitoring systems into damage control resuscitation is essential for improving survival outcomes in both military and civilian trauma settings.

 

 

The Critical Edge is for educational and informational purposes only and is not intended to diagnose, treat, cure, or prevent any disease, nor does it substitute for professional medical advice, diagnosis, or treatment from a qualified healthcare provider—always seek in-person evaluation and care from your physician or trauma team for any health concerns.

 

 

Targeted Resuscitation with TEG & ROTEM Comprehensive Study Guide

This study guide provides a comprehensive overview of the role of viscoelastic testing—specifically Thromboelastography (TEG) and Rotational Thromboelastometry (ROTEM)—in the identification and management of Trauma-Induced Coagulopathy (TIC). It synthesizes historical context, mechanical principles, clinical applications, and the shift from conventional testing to real-time, whole-blood analysis.

Overview of Trauma-Induced Coagulopathy (TIC)

Hemorrhage remains the primary cause of death in trauma patients. The "fatal triad" of hypothermia, acidosis, and trauma-induced coagulopathy (TIC) significantly worsens patient outcomes. Historically, clinicians relied on conventional coagulation tests (CCT) to manage these patients, but these methods often prove insufficient in the acute setting.

Modern management relies on Damage Control Resuscitation (DCR), a strategy focusing on balanced resuscitation, permissive hypotension, the use of whole blood, and hemostatic adjuncts. Viscoelastic testing is a cornerstone of DCR, providing rapid, real-time data to guide blood product administration.

Historical Evolution of Viscoelastic Testing

The field of viscoelastic testing has evolved from a research tool to a clinical standard in trauma care:

  • Origins: Hellmut Hartert first described TEG at the University of Heidelberg in 1948.
  • Clinical Integration: It was initially adopted in the 1960s for liver transplantations to identify hyperfibrinolysis and in the 1980s for cardiac surgery to manage anticoagulation and bleeding.
  • Application to Trauma: In 1997, Kaufmann et al. demonstrated the utility of TEG in trauma, showing it could predict transfusion needs and define coagulation abnormalities earlier than other methods.
  • Military and Civilian Expansion: Since 2001, military conflicts have accelerated knowledge regarding the resuscitation of injured soldiers. These advancements have been transferred to civilian trauma centers, leading to the widespread adoption of TEG and ROTEM.
    • Testing Mechanics and Modalities
    Rotational Thromboelastometry (ROTEM)

    ROTEM is a point-of-care analyzer that tests the hemostatic profile of whole blood. It functions by placing a blood sample in a cup with an oscillating sensor pin. As a clot forms, it restricts the pin's rotation, and this resistance is converted into a graphical display.

    ROTEM utilizes five specific assays to evaluate different pathways:

    • INTEM: Uses ellagic acid to activate the intrinsic pathway. It is sensitive to factors I, II, and VII through XII, as well as von Willebrand factor.
    • EXTEM: Uses tissue factor/thromboplastin to activate the extrinsic pathway. It is highly sensitive to fibrinolysis and evaluates factors II, VII, IX, and X.
    • FIBTEM: An EXTEM-based assay that adds cytochalasin D to inhibit platelets. This isolates the role of fibrin polymerization in clot formation.
    • HEPTEM: An INTEM-based assay that adds heparinase to neutralize heparin, allowing for the assessment of the underlying coagulation status in heparinized patients.
    • APTEM: An EXTEM-based assay that adds aprotinin to inhibit fibrinolysis. Comparing APTEM to EXTEM helps confirm true hyperfibrinolysis.
      • Thromboelastography (TEG)

      TEG uses a similar principle but often involves an oscillating cup and a stationary pin. The standard TEG uses kaolin to activate the coagulation cascade.

      • Rapid TEG (r-TEG): This variant adds tissue factor in addition to kaolin, significantly accelerating the activation process and providing faster results for emergency settings.
        • Conventional vs. Viscoelastic Testing

        There are several critical distinctions between Conventional Coagulation Tests (CCT) and viscoelastic testing (TEG/ROTEM):

        1. Sample Type: CCTs (like PT, INR, and aPTT) are performed on spun-down plasma, whereas TEG/ROTEM uses whole blood, capturing the interaction between plasma, platelets, and fibrin.
        2. Scope: CCTs target individual molecules or parts of the cascade and were originally designed to monitor therapies like heparin or warfarin. They do not address the integrated nature of the clotting process.
        3. Speed: CCTs are often slow, providing information on the patient's past status rather than their current state. TEG and ROTEM provide real-time, remote-viewable data, allowing for immediate intervention.
        4. Outcomes: Randomized controlled trials have shown that TEG-guided therapy improves survival, reduces hemorrhagic deaths, and leads to fewer blood transfusions compared to CCT-guided protocols.
          5. Clinical Interpretation and Directed Treatment

          Viscoelastic testing allows for targeted "goal-directed" resuscitation based on specific graphical and numerical parameters.

          Identifying and Correcting Deficiencies (TEG/r-TEG)
          • Delayed Initiation: A prolonged Reaction (R) time or Activated Clotting Time (ACT) indicates a factor deficiency or severe hemodilution, necessitating plasma transfusion.
          • Slow Clot Kinetics: A prolonged K time or a decreased alpha-angle suggests hypofibrinogenemia or platelet dysfunction. Treatment typically involves cryoprecipitate or fibrinogen concentrate.
          • Reduced Clot Strength: A low Maximum Amplitude (MA) reflects platelet dysfunction or low fibrinogen. This is treated with platelets and potentially cryoprecipitate or DDAVP.
          • Accelerated Clot Breakdown: An elevated LY30 (lysis at 30 minutes) indicates hyperfibrinolysis, requiring antifibrinolytics like tranexamic acid (TXA).
            • Identifying and Correcting Deficiencies (ROTEM)
            • Prolonged Clotting Time (CT): If CT is prolonged in INTEM or EXTEM, it indicates factor deficiency, requiring plasma.
            • Fibrinogen vs. Platelet Issues: A low A10 (amplitude at 10 minutes) in the FIBTEM assay points to hypofibrinogenemia, treated with cryoprecipitate. If FIBTEM A10 is normal but EXTEM A10 is low, it indicates platelet dysfunction, treated with platelet transfusion.
            • Lysis: An EXTEM Maximum Lysis (ML) of 15% or greater indicates hyperfibrinolysis, treated with TXA.
              • Specialized Pathological States
              Hyperfibrinolysis (HF)

              Hyperfibrinolysis is the excessive breakdown of clots, which is highly lethal in trauma.

              • Diagnosis: Defined by an LY30 ≥ 3% (TEG) or an EXTEM ML ≥ 15% (ROTEM).
              • Treatment: The CRASH-2 and STAAMP trials support the use of TXA within three hours of injury, particularly in patients with penetrating trauma or profound shock. Current expert consensus suggests a 2-g bolus of TXA for those with evidence of HF on admission.
                • Fibrinolysis Shutdown (SD)

                Fibrinolysis shutdown is a state where there is little to no clot breakdown (LY30 of 0% to 0.8%). While HF patients often die early from bleeding, SD patients face delayed mortality due to prothrombotic events, organ failure, and traumatic brain injury.

                Prothrombotic Risk and VTE

                High clot strength (elevated MA in TEG or MCF in ROTEM) is a strong predictor of venous thromboembolic events (VTE), such as pulmonary embolism. Research shows that patients with an admission MA > 72 are at a significantly higher risk, leading some centers to implement aggressive prophylaxis using aspirin and enoxaparin.

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                Glossary of Terms
                • A10 (Amplitude 10): The amplitude of the ROTEM tracing 10 minutes after the clotting time starts; used for early therapeutic decisions.
                • ACT (Activated Clotting Time): In r-TEG, the time in seconds between test initiation and initial fibrin formation.
                • Alpha-angle: The angle representing the speed of clot formation and fibrin cross-linking.
                • APTEM: A ROTEM assay that uses aprotinin to inhibit fibrinolysis in vitro.
                • CFT (Clot Formation Time): The time in ROTEM from the start of clotting (CT) until the clot reaches 20 mm in firmness.
                • CT (Clotting Time): The time from the addition of a reagent until the blood starts to clot in ROTEM.
                • EXTEM: A ROTEM assay that activates the extrinsic pathway via tissue factor.
                • FIBTEM: A ROTEM assay that uses a platelet antagonist to isolate fibrinogen contribution to clot strength.
                • HEPTEM: A ROTEM assay that uses heparinase to neutralize heparin effects.
                • INTEM: A ROTEM assay that activates the intrinsic pathway via contact activation (ellagic acid).
                • K time: The time in TEG from the start of clot formation until the curve reaches an amplitude of 20 mm.
                • LY30: The percentage of clot lysis 30 minutes after reaching maximum clot strength in TEG.
                • MA (Maximum Amplitude): The direct measure of the apex of the TEG curve, representing overall clot strength.
                • MCF (Maximum Clot Firmness): The ROTEM equivalent of MA; the greatest vertical amplitude of the tracing.
                • ML (Maximum Lysis): The percentage of fibrinolysis relative to the MCF in ROTEM.
                • R time (Reaction time): The period from the initiation of a TEG test until the beginning of clot formation.
                • TIC (Trauma-Induced Coagulopathy): A complex systemic failure of the coagulation process following severe injury.
                • TXA (Tranexamic Acid): An antifibrinolytic medication used to treat excessive clot breakdown.
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