ROTEM

Question 1

What is TEG and ROTEM?

Answer 1

Thromboelestography
Rotational thromboelastometry
Tools to assess whole blood clotting

Question 2

How do TEG/ROTEM work?

Answer 2

Whole blood at body temp is added to a heated cuvette
A pin is suspended into the cup
Rotation takes place
- TEG rotates the cup. ROTEM rotates the pin

Some impediment to the rotation develops as the blood clots.

Degree of impediment is recorded as amplitude and displayed on time vs. amplitude graph

Question 3

Some TEG nomenclatures 
R 
K 
A-angle 
TMA 
MA 
CLT 

What are they?

Answer 3

Reaction time - time from start to amplitude
Kinetic - time from 2mm amplitude to 20mm
A-angle - slope from 2mm to 20mm amplitude
Time to maximum amplitude
Maximum amplitude
Clot lysis time - time taken for amplitude to decrease by 2mm from MA

Question 4

What are some advantages of TEG/ROTEM?

Answer 4

Point of care, result in 10-20 mins
Theoretical reduction in use of blood products
measures fibrinolysis
Discriminates between coagulopathy due to thrombocytopenia vs. low fibrinogen
Similar cost to coag panel

Question 5

What are some disadvantages of TEG?

Answer 5

Needs training 
Poor precision 
Machine warms blood to 37 degrees, which will not reflect a hypothermic patient pathology 
Needs calibrating 3 times daily 
Regular servicing 
Consumables are expensive

Question 6

What does the Reaction Time (or clotting time on ROTEM) reflect?

Answer 6

Time it takes for the amplitude to start climbing.

Roughly relates to the time it takes for the enzymes of the clotting cascade to run their full course and arrive at the formation of fibrin from fibrinogen

Question 7

What prolongs reaction time?

Answer 7

Anything that causes a rise in PT and APTT
Direct thrombin inhibitor

Prolonged R prompts replacement of factors

Question 8

What does long clot formation time reflect?

Answer 8

Ineffective fibrin polymerisation, low platelet activity

Treat with platelet or cryoprecipitate - replace fibrinogen and platelet if prolonged

This is similar to the widened a angle

Question 9

What does the maximum amplitude reflect?

Answer 9

The maximum firmness of the clot, where the greatest impediment occurs

Mostly reflect the platelet count / activity

Question 10

When would you give tranexamic acid?

Answer 10

When the time to lysis time is shortened, which suggest early fibrinolysis