Introduction Hazardous risks accompanying the transfusion of heterogenous blood products and increasing shortage of blood products led to further search for better techniques of coagulation monitoring. Because of the limitations of standard coagulation tests, other techniques such as thrombelastography (TEG(r)) have been re-examined. TEG(r) was originally described by Hartert in 1948 (1). Continuous improvements of this technique over the decades made this test a valuable tool for the medical personnel interested in coagulation. The TEG(r) monitors hemostasis as a whole dynamic process instead of revealing information of isolated conventional coagulation screens (2). The TEG(r) measures the viscoelastic properties of blood as it is induced to clot under a low shear environment resembling sluggish venous flow. The patterns of changes in shear-elasticity enable the determination of the kinetics of clot formation and growth as well as the strength and stability of the formed clot. The strength and stability of the clot provides information about the ability of the clot to perform the work of hemostasis, while the kinetics determine the adequacy of quantitative factors available to clot formation. Principles of Thrombelastography The Computerized Thrombelastograph(r) Coagulation Analyzer (Haemoscope Corp. Skokie IL.) is a small instrument capable of running two samples simultaneously, easy to set up. It is connected to a computer (running the TEG(r) Analytical Software) through an A/D interface box . The coagulation profile is displayed on the screen as an outline of the Thrombelastograph(r) Coagulation Analyzer with the range of normal values displayed as dotted lines. The thromboelastogram is one of two clinically available viscoelastic tests that characterize formation and strength of the blood clot over time. The TEG(r) can measure in vitro the life of a clot, the time to initial clot formation, then evaluate a developing clot it’s acceleration phase, strengthening and retraction. TEG(r) can also detect clot lysis. A sample of celite activated whole blood (0.36 ml) is placed into a prewarmed cuvette. A suspended piston is then lowered into the cuvette which moves in rotation of a 4.5 degree arc backwards and forwards. The normal clot goes quite fast through an acceleration and strengthening phase. The fiber strands which interact with activated platelets attach to the surface of the cuvette and the suspended piston. The clot forming in the cuvette transmits its movement onto the suspended piston. A “weak” clot stretches and therefore delays the arc movement of the piston, which is graphically expressed as a narrow thromboelastogram. A strong clot in contrary will move the piston simultaneously and proportionally to the cuvettes movements, creating a thick thromboelastogram.
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