Thromboelastography (TEG)

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Lack of evidence suggests that these tests currently should be used ONLY FOR RESEARCH purposes in regards to trauma-induced coagulopathy.[1]

Background

  • Thromboelastography is used to identify acute coagulopathies in both traumatic and nontraumatic patients. This may enable focused use of blood products during resuscitation.
  • Quantifies the interaction of platelets with the coagulation cascade (aggregation, clot strengthening, fibrin cross linking and fibrinolysis).
  • 0.36mL of clotted blood from the patient is spun in a small cup with changes in the clot strength recorded electrically.
  • Two commercial types of viscoelastic tests are available:
    • Thromboelastography =TEG
    • Rotational thromboelastogram = ROTEM
  • Heparinase to deactivate heparin is now employed in the TEG(r) technology to prevent interference from heparin in samples[2]

Nomenclature Differences for ROTEM

Although TEG and ROTEM measure the same coagulation functions there is a different naming convention for each device.

ROTEM TEG
Clotting time (CT) R value (reaction time)
α angle and clot formation time (CFT) K value and α angle
Maximum clot firmness (MCF) Maximum amplitude (MA)
Clot lysis (CL) LY30

Features of a TEG Curve

Initiation (R)

Represents period of time of latency from start to initial fibrin formation due to effects of Factor VIIa and Tissue Factor.

Amplification (K)

Represents time taken to achieve a certain level of clot strength due to thrombin and activation of platelets (where r-time = time zero)

Propagation (α-Angle)

Measures the speed at which fibrin build-up and cross-linking takes place (clot strengthening), and hence assesses the rate of clot formation.

Maximum Amplitude (MA)

A function of the maximum dynamic properties of fibrin and platelet bonding via GPIIb/IIIa and represents the strongest point of fibrin clot and correlates to platelet function: 80% platelets; 20% fibrinogen.

Clot stability (LY 30%)

This is percentage decrease in amplitude 30 minutes post-MA and gives measure of degree of fibrinolysis

Normal Values[3]

  • R: 4-8 min
  • K: 1-4 min
  • α-Angle: 47-74°
  • MA: 55-73mm
  • LY 30%: 0-8%

Abnormal Values

Prolonged R

  • Factor deficiency (ie hemophilia)
  • Treat with FFP or protamine

Prolonged K/Reduced α-Angle

  • Fibrinogen deficiency (ie DIC)
  • Treat with cryoprecipitate

Reduced MA

  • Thrombocytopenia, platelet dysfunction (ie patient on clopidogrel)
  • Treat with platelets or DDAVP

Elevated LY 30%

  • Rapid clot lysis (ie tPA given)
  • Treat with TXA

TEG Diagram

Normal thromboelastogram

TEG Baylor Approach Algorithm[4]

TEG baylor approach corrected.jpg

See Also

External Links

References

  1. Hunt H, Stanworth S, Curry N, Woolley T, Cooper C, Ukoumunne O, Zhelev Z, Hyde C. TEG and ROTEM for diagnosing trauma‑induced coagulopathy (disorder of the clotting system) in adult trauma patients with bleeding. Cochcrane Review. 16 February 2015
  2. Milind Thakur, Aamer B Ahmed. A Review of Thromboelastography. International Journal of Perioperative Ultrasound and Applied Technologies, January-April 2012;1(1):25-29 Fulltext]
  3. Walsh M, Thomas SG, Howard JC, et al. Blood component therapy in trauma guided with the utilization of the perfusionist and thromboelastography. Journal of Extra-Corporeal Technology. 2011 Sep; 43(3):162-7.
  4. Tapia NM et al. TEG-guided resuscitation is superior to standardized MTP resuscitation in massively transfused penetrating trauma patients. J Trauma Acute Care Surg. 2013;74:378-386.