Download Thromboelastography

Thromboelastography
By
Mike Poullis
Measuring Coagulation Status
• Why do it?
• Benefits
• Need to understand the position of TEG in
coagulation assessment
Techniques
• Full blood count and Coagulation screen (APTT, PT, and
fibrinogen)
• Whole Blood tests
– Microaggregation
– Whole blood analysers
– Thrombelastography
• Purified Platelet tests
– Microaggregation
– Macroaggregation
– Platelet function analysers
• Skin bleeding time
Advantages of Techniques
• Full blood count and Coagulation screen (APTT, PT, and fibrinogen)
– Quick, easy, reproducible, understandable
• Whole Blood tests
•
MAJOR ADVANTAGE IS NO SAMPLE PREPERATION
– Microaggregation, Thrombelastography, and Whole blood
analysers
–
Easy
• Purified Platelet tests
– Microaggregation
– Macroaggregation
– Platelet function analysers
• Skin bleeding time
– Whole body answer
Easy
PRECISE DEFECT
PRECISE DEFECT
Limitations of Techniques
• Full blood count
– Number not function
• Coagulation screen (APTT, PT, and fibrinogen)
– 20 to 30 minutes, no fibrinolytic assessment
• Whole Blood tests
– Microaggregation
– Thrombelastography
No commercial kit
?sensitivity
• Purified Platelet tests
• YOU HAVE TO PREPARE THE PLATELETS
– Microaggregation
No commercial kit
– Macroaggregation
Experienced technician
– Platelet function analysers
?
• Skin bleeding time
– Invasive, not specific
Principles of
Thrombelastography
Celite (Kaolin) activated
Low shear environment
resembling sluggish
venous flow
Readout
What the numbers/letters mean
• R: is a period of time from initiation of the test to
the initial fibrin formation
• k: time from beginning of clot formation until the
amplitude of thromboelastogram reaches 20 mm
• alpha angle: The alpha angle represents the
acceleration (kinetics) of fibrin build up and crosslinking
• MA - Maximum amplitude strength of clot
(number function platelets fibrin)
• MA60: measures the rate of amplitude reduction
60 min. after MA (stability) of the clot
The Numbers and Letters
Tips and Tricks
• Heparinase
• Adding c7E3 Fab (ReoPro) to the TEG sample
will eliminate platelet function from the
thromboelastogram.
• Antifibrinolytic agents such as EpsilonAminocaproic Acid, Tranexamic acid and
Aprotinin
Example 1
Example 1 Answer
• Diagnosis: Delayed clot formation; suspect
1. heparin effect
2. factor deficiency
• Treatment: Measure an activated clotting time
(ACT) and repeat TEG with Heparinase.
1. if ACT prolonged: administer protamine
2. repeat TEG with Heparinase:
• if normal: administer protamine
• if abnormal or heparin not utilized in case:
administer FFP
Example 2
Example 2 Answer
• Diagnosis: Hypercoagulable state.
• Secondary to aggressive replacement of all
factors in platelet rich plasma
• Chronic dissection of aortic aneurysms
• Treatment: none
Example 3
Example 3 Answer
• Diagnosis: Weak Clot Formation
• Treatment: FFP, platelets and possible cryoprecipitate.
• Adding c7E3 Fab (ReoPro) to the TEG sample will
eliminate platelet function from the thromboelastogram.
The MA will become a function of fibrinogen activity.
• A repeat TEG should be performed post treatment.
Example 4
Heparinase
No Heparinase
Example 4 Answer
• Diagnosis: Heparin Effect. The top curve
represents a TEG with Heparinase (heparin
activity eliminated) and the bottom trace is the
same sample without Heparinase (an elevated
ACT will confirm the diagnosis).
• Treatment: Reverse the heparin and repeat the
TEG or reverse the heparin and perform an ACT.
Example 5
Heparinase
No Heparinase
Example 5 Answer
• Diagnosis: Normal Coagulation Profile. This is a
TEG from the same patient shown in example 4.
The heparin was reversed with protamine. The top
curve represents a TEG with Heparinase (heparin
activity eliminated) and the bottom trace is the
same sample without Heparinase. Since both
traces are identical all heparin was reversed by
protamine.
• Treatment: If there is still bleeding its surgical!
Example 6
Example 6 Answer
• Diagnosis: No clot formation
• Very low factor levels
• Heparin effect
• Treatment:
• repeat TEG with Heparinase :
1. if TEG normal: reverse heparin with protamine
2. if TEG abnormal: administer FFP
Example 7
Example 7 Answer
• Diagnosis: Poor coagulation and fibrinolysis
• Treatment: Administer coagulation factors and
antifibrinolytics (Tranexamic Acid or Aprotinin).
• The antifibrinolytics can be added to the TEG to
pre-evaluate their effectiveness.
• Repeat the TEG post treatment.
Example 8
Example 8 Answer
• Diagnosis: Technical error in processing TEG or
severe coagulopathy (correlate with clinical
scenario)
• Treatment: Repeat TEG
1. if normal: do nothing
2. if grossly abnormal and clinical bleeding:
administer all products (FFP, platelets,
cryoprecipitate) and repeat TEG.
Limitations
•
•
•
•
Still being evaluated
Paired pre and post operative TEGs
Still do lab tests
Celite and mechanical activation not
biochemical
• Wythenshaw, and Blackpool have TEG but
no communication on experience!
Clinical Common Sense
• Use same clinical skills to assess the
bleeding patient
• On Aspirin, Clopidogrel and Fragmin
•IGNORE THE TEG
Take Home Message 1
• Laboratory FBC, APTT, PT, and fibrinogen,
combined with a platelet function analyser
would have provided exact coagulation
deficit data!
Take Home Message 2
• If TEG is good, we need someone on call
who can use it, so as to aid coagulation
factor prescribing; we have had it since
March.