THROMBOELASTOGRAPHY

2. THROMBOELASTOGRAPHY
VISHNU AMBAREESH

3. • In surgery we have to manage
patients with a bleeding
diathesis in the preoperative,
intraoperative or
postoperative period.

4. • Complex surgical procedures
including cardiac and liver surgery
are associated with a potential for
significant perioperative blood loss
and the development of post
operative bleeding disorders.

5. • inherent risks of the use of
homologous blood and blood
products, and allied to the scarcity of
these resources, make it important
that treatment with blood products
is based on scientific evidence of
need.

6. • A variety of coagulation tests are used to
assess whole blood coagulation.

7. COAGULATION MONITORING
Conventional tests
•Tests of coagulation
*Platelets
• number
• function
*Clotting studies
• PT
• APTT
*Fibrinogen levels
•Tests of
fibrinolysis
* degradation
products

8. • Each of these tests measures a
different aspect of the clotting
process, but even in combination
they do not provide a complete
picture of the status of the
coagulation system

9. • Besides evaluation of platelet
function remains insensitive and
time consuming. The platelet
count provides only a
quantitative, not qualitative index
of platelet status.

10. • At present the treatment of postoperative
bleeding remains empirical because of the
perceived need for immediate correction of
the haemostatic defect and lack of readily
available measures of all phases of clot
formation and breakdown , including the
strength of the clot
• FFP and platelets often given with little
scientific basis.

11. What we need?
an effective and convenient means of
monitoring whole blood coagulation
which evaluates the elastic properties of
whole blood and provides a global
assessment of heamostatic function.

12. THROMBOELASTOGRAPHY

13. • First developed by Dr. Hellmut Hartet at
University of Heidelberg, School of Medicine
in 1948 as a method to assess global
haemostatic function from a single blood
sample; this was the original
thromboelastography

14. WHAT IS THROMBOELASTOGRAPHY
Functional Description
• Thromboelastography monitors the
thrombodynamic properties of blood as it is
induced to clot under a low shear environment
resembling sluggish venous flow. The patterns of
change 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.

15. • The strength and stability of the clot
provide information about the ability of
the clot to perform the work of
haemostasis, while the kinetics
determine the adequacy of quantitative
factors available to clot formation

16. • In classical thrombelastography, a small
sample of blood (typically 0.36 ml) is placed
into a cuvette (cup) which is rotated gently
through 4º 45´ (cycle time 6/min) to imitate
sluggish venous flow and activate coagulation.
When a sensor shaft is inserted into the
sample a clot forms between the cup and the
sensor. The speed and strength of clot
formation is measured in various ways (now
usually by computer)

19. • The patterns of changes in strength
and elasticity in the clot provide
information about how well the
blood can perform hemostasis (the
halting of blood flow), and how well
or poorly different factors are
contributing to clot formation.

20. THROMBOELASTOGRAPHY
Basic Principles
• Heated (37C) oscillating cup
• Pin suspended from torsion
wire into blood
• Development of fibrin strands
“couple” motion of cup to pin
• “Coupling” directly
proportional to clot strength
•  tension in wire detected by
EM transducer

21. THROMBOELASTOGRAPHY
Basic Principles
• Electrical signal amplified to
create TEG trace
• Result displayed graphically
on pen & ink printer or
computer screen
• Deflection of trace increases
as clot strength increases &
decreases as clot strength
decreases

24. THROMBOELASTOGRAPHY
Refinements to Technique
• TEG accelerants / activators / modifiers
• Celite / Kaolin / TF accelerates initial coagulation
• Reopro (abciximab) blocks platelet component of
coagulation
• Platelet mapping reagents modify TEG to allow analysis of
Aspirin / Clopidigrol effects
• Heparinase cups
• Reverse residual heparin in sample
• Use of paired plain / heparinase cups allows identification
of inadequate heparin reversal or sample contamination

25. THROMBOELASTOGRAPHY
The “r” time
r time
•represents period of time of
latency from start of test to
initial fibrin formation
•in effect is main part of
TEG’s representation of
standard”clotting studies”
•normal range
• 15 - 23 mins (native
blood)
• 5 - 7 mins (kaolin-activated)

26. THROMBOELASTOGRAPHY
What affects the “r” time?
•r time  by
• Factor deficiency
• Anti-coagulation
• Severe
hypofibrinogenaemia
• Severe
thrombocytopenia
•r time  by
• Hypercoagulability
syndromes

27. THROMBOELASTOGRAPHY
The “k” time
k time
•represents time taken to
achieve a certain level of clot
strength (where r time =
time zero ) - equates to
amplitude 20 mm
•normal range
• 5 - 10 mins (native
blood)
• 1 - 3 mins (kaolin-activated)

28. THROMBOELASTOGRAPHY
What affects the “k” time?
•k time  by
• Factor deficiency
• Thrombocytopenia
• Thrombocytopathy
• Hypofibrinogenaemia
•k time  by
• Hypercoagulabili
ty state

29. THROMBOELASTOGRAPHY
The “” angle
 angle
•Measures the rapidity of
fibrin build-up and cross-linking
(clot strengthening)
•assesses rate of clot
formation
•normal range
• 22 - 38 (native
blood)
• 53 - 67(kaolin-activated)

30. THROMBOELASTOGRAPHY
What affects the “” angle?
• Angle  by
• Hypercoagulable
state
• Angle  by
• Hypofibrinogenemia
• Thrombocytopenia

31. THROMBOELASTOGRAPHY
The “maximum amplitude” (MA)
Maximum amplitude
•MA is a direct function of the
maximum dynamic properties of
fibrin and platelet bonding via
GPIIb/IIIa and represents the
ultimate strength of the fibrin
clot
•Correlates to platelet function
• 80% platelets
• 20% fibrinogen
•normal range
• 47 – 58 mm (native blood)
• 59 - 68 mm (kaolin-activated)

32. THROMBOELASTOGRAPHY
What affects the “MA” ?
•MA  by
• Hypercoagulable
state
•MA  by
• Thrombocytopenia
• Thrombocytopathy
• Hypofibrinogenemia

33. THROMBOELASTOGRAPHY
Fibrinolysis
•LY30
•measures % decrease
in amplitude 30 minutes
post-MA
•gives measure of
degree of fibrinolysis
•normal range
• < 7.5% (native
blood)
• < 7.5% (celite-activated)
•LY60
• 60 minute post-
MA data

34. THROMBOELASTOGRAPHY
Other measurements of Fibrinolysis
•A30 (A60)
• amplitude at 30 (60) mins
post-MA
•EPL
•earliest indicator of
abnormal lysis
•represents “computer
prediction” of 30 min lysis
based on interrogation of
actual rate of diminution of
trace amplitude commencing
30 secs post-MA
•early EPL>LY30 (30 min
EPL=LY30)
•normal EPL < 15%

35. THROMBOELASTOGRAPHY
What measurements are affected by
fibrinolysis?
•Fibrinolysis leads to:
•  LY30 /  LY60
•  EPL
•  A30 /  A60

36. THROMBOELATOGRAPHY
Quantitative analysis
• Clot formation
– Clotting factors - r, k times
• Clot kinetics
– Clotting factors - r, k times
– Platelets - MA
• Clot strength / stability
– Platelets - MA
– Fibrinogen - Reopro-mod MA
• Clot resolution
– Fibrinolysis - LY30/60; EPL
A30/60

37. THROMBOELATOGRAPHY
Qualitative analysis

38. TEG v CONVENTIONAL STUDIES
• Conventional tests
• test various parts of
coag cascade, but in
isolation
• out of touch with current
thoughts on coagulation
• plasma tests may not be
accurate reflection of
what actually happens in
patient
• difficult to assess
platelet function
• static tests
• take time to complete 
best guess or delay
treatment
• TEG
• global functional
assessment of coagulation
/ fibrinolysis
• more in touch with
current coagulation
concepts
• use actual cellular
surfaces to monitor
coagulation
• gives assessment of
platelet function
• dynamic tests
• rapid results  rapid
monitoring of intervention

39. Advantages of TEG over conventional
coagulation monitoring
• It is dynamic, giving information on entire
coagulation process, rather than on isolated part
• It gives information on areas which it is
normally difficult to study easily – fibrinolysis
and platelet function in particular
• Near-patient testing means results are rapid
facilitating appropriate intervention
• It is cost effective compared to conventional
tests

40. ROTEM
• Rotational thromboelastography uses a
modification of TEG, signal of the pin is
transmitted using an optical detecter instead a
torsion wire.
• Movement orginates from pin and not the cup
• Uses an electronic pippette which improves
reproducibility and performance

41. • In ROTEM the sensor shaft rotates rather tha
the cup
• avoids limitations of traditional instruments
esp. susceptibility to mechanical shocks and
vibrations.
• However TEG is rated as the best compromise
between usability, usefulness and cost as
compared to ROTEM

43. SONOCLOT
• Sonoclot incorporates a very sensitive
visco-elastic detection system which is
very sensitive to the changes in the
developing clot. It gives more detailed
information as compared to
Thromboelastograph

44. • PRINCIPLE
measures the changing impedence to
movement imposed by the developing clot on
a small probe vibrating at an ultrasonic
frequency in a coagulating blood sample.

46. THANK YOU!!!!