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

[3] Normal Values

R: 4-8 min

4-8 min K: 1-4 min

1-4 min α-Angle: 47-74°

47-74° MA: 55-73mm

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

[4] TEG Baylor Approach Algorithm

See Also