With respect to thromboelastography and haemostasis:
The image depicted in Figure 1 represents a normal thromboelastogram.
With reference to the parameters labelled in Figure 1:
i. CT (or R)
ii. CFT (or K)
iii. Alpha angle
iv. MCF (or MA)
v. LI30 (or LY30 or CL)
a) Explain what each parameter represents and what it measures. (60% marks)
Review the following thromboelastograms labelled A – E.
Diagram A represents a normal coagulation profile.
b) Describe the coagulation status indicated by diagrams B – E. (40% marks)
R (reaction time or clotting time) is the time elapsed until first measurable clot forms (amplitude of 2mm) and indicates the initiation of haemostasis and is dependent on presence of clotting factors.
K (kinetics or clot formation time) is the time taken to achieve a certain level of clot firmness (amplitude of 20mm) and indicates amplification of the clotting process. Dependent on fibrinogen.
Alpha angle reflects the speed of fibrin accumulation. Dependent on fibrinogen.
MA/MCF is the maximum amplitude or maximum clot firmness and is the highest vertical amplitude of the TEG tracing. Dependent on platelets and fibrin.
LY30 /CL (clot lysis) is the percentage of amplitude reduction 30 min after maximum amplitude and is a measure of fibrinolysis.
B – Anticoagulant therapy or factor deficiency
C – Platelet dysfunction or thrombocytopaenia or fibrinogen deficiency
D – Fibrinolysis e.g. use of t-PA
E – Hypercoagulable state
In short form:
CT and R values:
CFT and K values:
Maximum clot firmness (MCF) and maximum amplitude (MA):
LY30 and CL (or CLT)
As for the examples:
A is a normal-looking TEG
B has an extremely prolonged CT, but a normal α-angle and a reasonably normal MCF. One might surmise that either something is missing among the clotting factors, or there is some inhibitor present. The platelet count and fibrinogen levels are probably near normal. One might find such a picture in a patient on warfarin, heparin, or receiving a direct thrombin inhibitor.
C is a TEG of a patient who has plenty of clotting factors; the reaction starts quickly. The MCF is inadequate, suggesting that platelet dysfunction (or thrombocytopenia) are to blame. The college mention that there may also be a problem with the fibrinogen level, but the good α-angle would suggest otherwise.
D is a TEG of a patient with hyperfirbrinolysis from whatever cause.
E is a patient with a hypercoagulable state; the blood clots quickly, with a very firm clot generated in no time.
The LITFL page for TEG is ideal to answer this question: they have lovely TEG silhouettes available for the "important patterns".
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