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• TEG is a point of care test, to evaluate the ability of the blood to form clots. It was first developed in Germany by Hellmut Harter in 1948.

• Modern TEG records the kinetic changes of clot formation, retraction & lysis.

• The principle : TEG measures clot formation via the tensile strength of fibrin-polymer-platelet complex.

• PROCEDURE : The specimen is placed in a sample cup. A metal pin goes to the center of the cup. The contact of the blood to walls of the cup or addition of clot activator like celite, initiates a clot formation. The instrument then rotates the cup in an oscillating fashion, 4.45 degrees every 10 seconds. As fibrin & platelet aggregates form, they connect the inside of the cup with the metal pin, transferring the energy used to move the cup in the pin. A torsion wire connected to the pin measures the strength of the clot over time, with the magnitude of the output directly proportional to the strength of the clot. Lysis or retraction of the clot decreases the strength of the clot .

INTERPRETATION

 

Parameters

• Maximum amplitude (MA) : They reflect overall maximum strength of the clot.

• R time (Reaction time): Time taken from enzymatic activation of clotting cascade to the formation of fibrin strand polymer.

• K time (Kinetic time): It is the period from start of clot formation until the curve reaches an amplitude of 20mm.

• α-angle: Kinetics of fibrin formation and cross linking are expressed by the α-angle, which is the angle between the baseline and the tangent to TEG curve.

• The degree of fibrinolysis is reflected by the difference between the maximal amplitude and the amplitude measured after 30 -60 minutes.



 

Clinical Application

• Liver transplantation : It is useful for liver transplant patients who are at the risk of bleeding. They have coagulation factor deficiency. Due to hypersplenism they will also have thrombocytopenia. The reperfusion of the graft liver causes endothelial injury and increases tPA levels thereby increasing fibrinolysis as well. Circulating heparin also reduces the clot formation.

• Cardiac surgery:

• TEG & anti platelet : As MI patients are on aspirin it is stopped by a period of 10 days prior to CABG but a considerable no. of patients bleeds during the surgery & TEG helps to diagnose patients at risk of bleeding.

• Hypercoagulable state : They also be used to monitor the hypercoagulable state produced after surgery.

Updated on:12/1/2015

Reference

Annual update in intensive care and Emergency Medicine. 2014. By J.L. Vincent