II. Indications
-
Massive Hemorrhage related transfusions
- May assist in determining ratio of Red Blood Cell Transfusions to Fresh Frozen Plasma and Platelet Transfusion
- Preferred over older markers of coagulation (INR, PTT)
III. Mechanism
- Whole blood assay of a blood's ability to clot based on viscoelastic blood properties
- As blood clot forms, analyzer detects resistance over time
- Analyzer plots measurized resistance over time in form of a graph
- Typically graph is plotted over a 20-30 minute period until maximal clot firmness
- Predicts bleeding and thrombosis risk
- Also identifies hyperfibrinolysis
IV. Labs: Bedside Viscoelastic Assay
- Thromboelastography (TEG)
- Reported as reaction time (R)
- Rapid Thromboelastography (r-TEG)
- Reported as Activated Clotting Time (ACT)
- Assay is faster than TEG due to added tissue factor and Kaolin (speeds clotting activation)
- Initial results available within 3 minutes (final results in 30 minutes)
- Detector wire protrudes into a small sample of blood (350 ul) in oscillating cup at 37 C
- Rotational Thromboelastography (ROTEM)
V. Interpretation: General
- Abnormal Clotting Time
- In early trauma Coagulopathy, often related to plasma related deficiencies
- In later trauma Coagulopathy, Fibrinogen deficiency may be treated with Cryoprecipitate or Fibrinogen
- Poor maximal clot firmness (poor maximal amplitude)
- Consider Platelet Transfusion
- Hyperfibrinolysis
- Typically assumed as a part of early trauma Coagulopathy, and Tranexamic Acid is given empirically
- May appear as abnormal clot breakdown over time (typically subtle in graph)
VI. Precautions
- Viscoelastic Assays do not measure Platelet inhibition by antiplatelet agents (e.g. Aspirin, Clopidogrel)
VII. Interpretation: Rapid Thromboelastography (r-TEG)
- Activated Clotting Time (ACT or R-Time)
- Normal 0-118 seconds
- Represents Clotting Factor acivity and initial Fibrin formation (most important rTEG result in Hemorrhage)
- Decreased in Hypercoagulable state
- Increased in Clotting Factor deficiency, severe hemodilution (consider FFP)
- K-Time
- Normal 1-2 min
- Represents time to initial clot strength target (measures Fibrin and Platelet interaction)
- Prolonged in Fibrinogen or Platelet deficiency (consider Platelet Transfusion)
- Alpha angle
- Normal 66 to 82 degrees
- Represents slope of Clot Formation (Fibrin formation and Platelet-Fibrin interaction)
- Low angles (decreased slope) reflects slow Fibrin formation
- Decreased in Fibrinogen or Platelet deficiency (consider Platelet Transfusion or Cryoprecipitate)
- Maximum Amplitude (mA)
- Normal 54 to 72 mm
- Represents greatest clot strength and Platelet function
- Decreased in Fibrinogen or Platelet deficiency (consider Platelet Transfusion, Cryoprecipitate, DDAVP)
- Increased in excess Platelet activity
- G-Value
- Normal 5.3K to 12.4K dynes/cm2
- Overall clot strength measure (used by paramedics in prehospital setting)
- Increased in Hypercoagulable states and decreased in hypocoagulable states
- Ly30 (Lysis Time, Estimated Percent Lysis, EPL)
- Normal <3 to 7.5% (clinically important at >3%)
- Measured amplitude reduction (percent) at 30 minutes following Maximum Amplitude (mA)
- Reflects clot stability and firmness
- Increased (>3%) in hyperfibrinolysis (consider TXA if <3 hours from time of injury)
- Ly30 >3% is an important prognostic indicator in Hemorrhagic Shock
- Markedly increased all cause mortality
- Cripps (2013) J Trauma Acute Care Surg 75(2 Suppl 2): S255-62 [PubMed]
VIII. Resources
- Shaydakov, Sigmon, Blebea (2019) Stat Pearls
IX. References
- Freeman and Bourland (2021) Crit Dec Emerg Med 35(12): 3-11
- Swaminathan and Hicks in Herbert (2020) EM:Rap 20(7): 1-2
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Related Studies
| Definition (MSH) | Substances that display the physical properties of ELASTICITY and VISCOSITY. The dual-nature of these substances causes them to resist applied forces in a time-dependent manner. |
| Concepts | Chemical Viewed Functionally (T120) |
| MSH | D055682 |
| English | Viscoelastic Substances, Substances, Viscoelastic |
| Spanish | Sustancias Viscoelásticas |
| French | Substances viscoélastiques, Matières visco-élastiques, Matières viscoélastiques, Substances visco-élastiques |
| Italian | Sostanze viscoelastiche |
| Russian | ВЯЗКОЭЛАСТИЧНЫЕ ВЕЩЕСТВА, VIAZKOELASTICHNYE VESHCHESTVA, ВЯЗКОУПРУГИЕ ВЕЩЕСТВА, VIAZKOUPRUGIE VESHCHESTVA |
| German | Viskoelastische Substanzen |
| Portuguese | Substâncias Viscoelásticas, Agentes Viscoelásticos |
| Swedish | Viskoelastiska substanser |
| Czech | viskoelastické látky |
| Polish | Substancje wiskoelastyczne, Roztwory wiskoelastyczne, Pianki wiskoelastyczne |
| Japanese | 粘弾性溶液, 粘弾性物質, 粘弾性フォーム |
Ontology: Thromboelastography panel (C3258239)
| Concepts | Laboratory Procedure (T059) |
| LNC | LP133932-6, MTHU041635 |
| English | Thromboelastography panel |
