Thromboelastography

TEG = thromboelastography

ROTEM = rotational thromboelastometry

Both TEG and ROTEM are methods of measuring coagulation and fibrinolysis.  In TEG, the “cup” of the machine rotates, whereas in ROTEM, it is the sensor shaft that rotates. 

In thromboelastography, blood is rotate by 4`45″ 6x per minute to simulate sluggish blood flobe.  A wire probe is then used to measure the speed of coagulation and extent of fibrinolysis.

Thromboelastography measures 4 parameters of blood coagulation (reaction time, K value, alpha angle and maximum amplitude) and 2 parameters of clot lysis (estimated percentage of lysis and percent clot lysed after 30 minutes).  Two other values are calculated based on a proprietary formula from the company who created the machine (coagulation index).

  

The parameters for clot formation:

1.  Reaction time (R) – time to first clot detected, reflects coagulation factor activity

2.  K value (K) – time from (R) until clot reaches 20mm, reflects speed of clot formation

3.  alpha angle (A) – the tangent of the curve when K is reached, also reflects speed of clot formation; represents thrombin burst and conversion of fibrinogen to fibrin

4.  maximum amplitude (MA) – reflects clot strength; 80% is dervied fro platelet function and 20% from fibrin

The calculated parameters:

1.  COAGULATION INDEX (CI)

2.  G VALUE – log-derivation of MA, also represents clot strenght using dynes/sec as units;  rising levls may be seen in venous thromboembolic disease

The parameters for clot lysis:

1.  Estimated % lysis (EPL)

2.  % clot lysed after 30 minutes (LY30%)

   
Based on the TEG values, the following treatments may be given:

1.  Elevated R – give plasma

2.  decreased  alpha angle – give cryoprecipitate or large volume of plasma

3.  decreased MA – platelet transfusion or DDAVP

4.  increased EPL or LY30% – treat with antifibrinolytics (i.e. tranexamic acid or aminocaproic acid)
    
    
 

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