TEG LAB Flashcards
What is a TEG test?
Thromboelastography (TEG) is a method of testing the efficiency of blood coagulation. It is a test mainly used in surgery and anesthesiology, although few centers are capable of performing it.
What is TEG in trauma?
TEG and ROTEM for diagnosing trauma‑induced coagulopathy (disorder of the clotting system) in adult trauma patients with bleeding. Trauma-induced coagulopathy (TIC) is a disorder of the blood clotting process that can occur soon after trauma injury that can lead to the patient bleeding to death.
What is TEG platelet mapping?
The whole blood TEG® Platelet Mapping™ assay measures clot strength as maximal amplitude (MA) and enables for quantification of platelet function, including the contribution of the adenosine diphosphate (ADP) and thromboxane A2 (TxA2) receptors to clot formation.
TEG® measures
the physical properties of the clot in whole blood via a pin suspended in a cup (heated to 37C) from a torsion wire connected with a mechanical-electrical transducer
TEG shows
the interaction of platelets with the coagulation cascade (aggregation, clot strengthening, fibrin cross-linking and fibrinolysis)
The elasticity and strength of the developing clot changes the rotation of the pin, which is converted into
electrical signals that a computer uses to create graphical and numerical output
point of care test (quick, takes around
30min)
Maybe useful in:
trauma (reduction in blood product use and mortality in cohort studies)
obstetrics (some data to show that it may decrease transfusion rates; this is controversial)
early detection of dilutional coagulopathy
Indications
prediction of need for transfusion (maximum amplitude (MA) is a useful predictor in trauma)
guide transfusion strategy
Studies show cost-effectiveness and reduction in blood products in:
liver transplantation
cardiac surgery
TEG® VERSUS ROTEM®
Two commercial types of viscoelastic tests are available: thromboelastography =TEG® (developed in 1948, now produced in the USA) and rotational thromboelastogram = ROTEM® (from Germany)
differences in diagnostic nomenclature for identical parameters between the two
TEG® operates by moving a cup in a limited arc (±4°45′ every 5s) filled with sample that engages a pin/wire transduction system as clot formation occur
ROTEM® has an immobile cup wherein the pin/wire transduction system slowly oscillates (±4°45′every 6s)
results are not directly comparable as different coagulation activators are used
ROTEM® is more resistant to mechanical shock, which may be an advantage in the clinical setting
How is a TEG performed?
In order to perform a TEG, a citrated-sample of whole blood is placed into a heated sample cup with calcium chloride (to overcome the effects of the citrate), kaolin (a negatively charged molecule known to initiate the intrinsic pathway10), and phospholipids (required for optimal functioning of the extrinsic pathway11) (Figure 2). As the sample cup oscillates in a limited arc, formation of clot results in the generation of rotational forces on a pin suspended from a torsion wire. Forces translated to the torsion wire are then, in turn, transmitted to an electrical transducer, creating a characteristic waveform
I’ve heard of the Rapid TEG (r-TEG), is there a Difference?
When performed by a trained laboratory specialist, an r-TEG may be completed within 15 minutes as compared to the average 30-45 minutes processing time for a standard TEG.4,5,14 In contrast to a TEG, whole blood samples for an r-TEG may be performed with citrated or non-citrated samples.4 Samples utilized for an r-TEG are combined with tissue factor (activating the extrinsic pathway), and kaolin (activating the intrinsic pathway as above) +/- calcium chloride as applicable.
I’ve also heard of ROTEM, what is it?
Although utilizing the technique developed by Dr. Harter, rotational thromboelastometry (ROTEM) differs from traditional thromboelastography in its mechanical application. Unlike traditional thromboelastography, which utilizes a sample cup rotating in a limited arc, ROTEM employs a static sample cup with an oscillating pin/wire transduction system. By comparison, ROTEM is also a more complex diagnostic test as it requires a number of differing reagents.
Why Might an Emergency Medicine Physician Want to Know about this Test?
Coagulation abnormalities in trauma patients have demonstrated a significant association with infection, multi-organ failure, and death.15-18 Given its ability to quickly detect hematologic pathology, the TEG is becoming a tool for the evaluation of transfusion requirements/coagulopathy post transfusion in this patient population.
