Thromboelastography- r value k value LA30 maximum amplitude

thromboelastography
process
principle
r value k value
maximum amplitude LA30
ROTEM
indications

1. Thromboelastography (TEG) Presenter- Dr. Shiny Moderator- Dr. Nidhi Bansal

2. Thromboelastography (TEG) is a viscoelastic hemostatic assay that measures – the viscoelastic properties of whole blood clot formation. Interaction of platelets with the coagulation cascade (aggregation, clot strengthening, fibrin cross-linking and fibrinolysis). the functional ability of the blood to make a hemostatic plug. Analysis of real-time blood coagulation parameters.

3. PRINCIPLE The principle of this in vitro test is to detect and quantify dynamic changes of the viscoelastic properties of a blood sample during clot formation under low shear environment.

4. Kaolin, an inert silicate, negatively charged particulate activator of the intrinsic clotting pathway. Kaolin promotes clotting by activating Factor XII , in which it initiates the intrinsic clotting cascade via activating Factor XI and ends with the formation of a fibrin clot. In addition, kaolin can also promote the activation of platelet-associated Factor-XI to initiate the intrinsic clotting cascade normally in Factor XII-deficient patients. KAOLIN (reagent used in TEG)

5. Mechanism of instrument Each chamber consists of a platform with a disposable cup where a blood sample is placed and a detection pin suspended in its centre. The cup oscillates around the detection pin in a limited arc of +/- 4 degrees 45' every 5 seconds. Induced pin movement is recorded, and changes are measured as a function of time.

6. PROCESS (how to operate TEG) Insert Cup and pin in the TEG machine. 1ml of citrated blood added in kaolin vial addition of 20 uL of 0.2M calcium chloride in disposable TEG cup and analyse graph. 340 uL of blood from kaolin vial is pipetted to the TEG cup Machine in test position. Initialize test for 60-90 min.

7. Cup oscillates around submerged torsion pin which suspended in a cup (heated to 37C) from a torsion wire connected with a mechanical-electrical transducer which is connected to a computer. As coagulation occurs, pin adheres to clot and begins to move with it. Magnitude of pin motion directly proportional to strength of the clot. Pin motion is displayed graphically by the computer. Torsion pin remains motionless until clotting begins.

8. Parameters R value = reaction time (s) time from start of test to initial fibrin formation (amplitude of 2mm) initiation phase dependent on clotting factors Prolongation of the R time reflects deficiency of coagulation factors that may be corrected by fresh frozen plasma (FFP) transfusion.

9. K = kinetics (s) Time taken to achieve a certain level of clot strength (20mm) Amplification phase Dependent on fibrinogen Prolongation of the K time, suggests a deficiency of fibrinogen and may be corrected by cryoprecipitate or fibrinogen concentrate.

10. Alpha angle (slope of line between R and K) rate of clot formation “thrombin burst” / propagation phase dependent on fibrinogen a decrease of the alfa angle, suggests a deficiency of fibrinogen and corrected by cryoprecipitate or fibrinogen concentrate

11. MA = maximum amplitude (mm) represents the ultimate strength of the fibrin clot; i.e. overall stability of the clot dependent on platelets (80%) and fibrin (20%). Low MA indicates a quantitative or functional deficiency of platelets and could be corrected by platelet transfusion.

12. LY30 = amplitude at 30 minutes percentage decrease in amplitude at 30 minutes post-MA fibrinolysis phase clot lysis time(CLT) (s) an increased LY value implies activated fibrinolysis that may be treated by fibrinolysis inhibitors ( aminocaproic or tranexamic acid).

13. Approximate normal values R: 4-8 min K: 1-4 min α-Angle: 47-74° MA: 55-73mm LY 30%: 0-8%

14. Disease Analysis with TEG

15. HAEMOPHILIA

16. Thrombocytopenia/low platelet count

17. HYPERCOGULATION

18. HYPOCOGULATION

19. Modifications of the classic TEG Rapid TEG (r-TEG) utilizes tissue factor instead of the kaolin reagent to activate blood coagulation. Because tissue factor triggers the extrinsic coagulation pathway , which involves a smaller number of coagulation factors, So this test can be performed faster than conventional TEG. Rapid TEG can be completed within 15 minutes. heparinase TEG ( hTEG ) measures the effect of heparin reversal on blood coagulation.

20. ROTEM® - Rotational thromboelastometry (from Germany) ROTEM® has an immobile cup wherein the pin/wire transduction system slowly oscillates (±4°45′every 6s). In this assay, some different activator reagents are utilized to investigate specific components of the coagulation pathway. ROTEM® is more resistant to mechanical shock, which may be an advantage in the clinical setting.

21. Equivalent variables for ROTEM® Clotting time (CT) = R  time Clot formation time (CFT) = K  value Maximum clot firmness (MCF)  = Maximum amplitude (MA) Clot lysis (CL)  = LY30

22. Advantage The main advantage of TEG testing is its potential to deliver immediate goal-oriented and individualized care to a bleeding patient. Global assessment of blood coagulability , including coagulation cascade, platelet function, and fibrinolysis Rapid real-time simple methodology & easy to handle. Guide to transfusion therapy Predict the clinical efficacy of therapeutic agents affecting blood coagulability. The overall goal of the TEG® system is to reduce thrombotic complications leading to improved patient outcomes.

23. Clinical Significance The main advantage of TEG testing is its potential to deliver immediate goal-oriented and individualized care to a bleeding patient. TEG has been used to predict early transfusion requirements of trauma patients predict bleeding after cardiac surgery, kaolin-activated TEG was demonstrated to be more useful. Predict the clinical efficacy of therapeutic agents affecting blood coagulability .

24. Limitations TEG measures blood coagulation in vitro, with or without an additional activator. Blood coagulation also depends on the size of the injured vessel, blood flow characteristics, and local vessel wall biology that determines the quantity and functional activity of the membrane-bound coagulation factors. TEG has a sensitivity and specificity that may vary significantly in different populations.

25. Patients taking anticoagulants and antiplatelet agents are a major concern in the trauma setting. Ex. Warfarin is a commonly prescribed medication that has been associated with increased mortality in trauma patients. In about half of patients on warfarin therapy, R-time may be normal in TEG. This is a good example of how TEG may miss a clinically significant coagulopathic state.

26. Clinical Guidelines NICE guidelines recommend thromboelastography to help detect, manage and monitor hemostasis in cardiac surgery patients. Other clinical guidelines do not currently strongly recommend TEG for use in other settings due to the lack of high-quality evidence.

27. Thank you