10: Haemostasis

Question 1

How do platelets adhere to the vessel wall?

Answer 1

By vWF

Question 2

What is the end point of platelet plug formation?

Answer 2

Fibrinogen to fibrin

Question 3

What happens to blood vessels immediately following injury?

Answer 3

Reflex vasoconstriction

Question 4

Where is vWF exposed from following injury?

Answer 4

The subendothelial matrix

Question 5

Where are clotting factors produced?

Answer 5

Liver

Question 6

Which factors require vitamin K?

Answer 6

II, VII, IX, X

Question 7

What is the target for rodenticides?

Answer 7

Vitamin K

Question 8

What is the end-point of the coagnulation cascade?

Answer 8

Produce thrombin to catalyse fibrin production

Question 9

Which tests evaluate the intrinsic and common pathways?

Answer 9

APTT/ACT

Question 10

Which test evaulates the extrinsic pathway?

Answer 10

OSPT

Question 11

What activates the intrinsic pathway?

Answer 11

Negatively charged surface

Question 12

What activates the extrinsic pathway?

Answer 12

Tissue factor

Question 13

Which pathway is the most important initiator of secondary coagulation?

Answer 13

Extrinsic

Question 14

What activates factor VII?

Answer 14

Exposure to tissue factor

Question 15

What does factor VII activation cause?

Answer 15

Rapid thrombin burst

Question 16

What is the function of the intrinsic pathway?

Answer 16

Amplification - causes cascade of activation via common pathway

Question 17

Which factors does thrombin activate?

Answer 17

V, VIII, IX but also their inhibitors protein C and protein X

Question 18

How does factor XIII stabilise the clot?

Answer 18

Forms covalent bonds that crosslink fibrin

Question 19

Which breed gets hyperfibrinolytic disorders?

Answer 19

Greyhounds

Question 20

What is activated by fibrinogen to cause fibrinolysis?

Answer 20

Plasmin

Question 21

What does fibrinolysis result in production of?

Answer 21

FDPs e.g. D dimers

Question 22

What are clinical signs or primary coagulation disorder?

Answer 22

Petechiae/ecchymoses, epistaxis, GI bleed

Question 23

Below what platelet count do you see clinical signs in primary coagulation disorder?

Answer 23

30-50

Question 24

Why are signs more severe in secondary coagulation disorder?

Answer 24

No stabilisation

Question 25

What are some complications of secondary coagulation disorders?

Answer 25

Cavity bleed, haematomas

Question 26

What should you test if primary coagulation disorder?

Answer 26

Platelets

Question 27

What should you test if secondary coagulation disorder?

Answer 27

Clotting factors

Question 28

What is a normal number of platelets per 100x field?

Answer 28

10-15

Question 29

Below what platelet count per 100x field is there a risk of bleeding?

Answer 29

3-5

Question 30

Which test should you not do in thrombocytopenia?

Answer 30

BMBT - check platelet count first

Question 31

Why shouldn't you do a cuticle bleed test in primary coagulation disorder?

Answer 31

If accidentally cut and arteriole it will involve secondary haemostasis so not a good test

Question 32

Which are the most important tests for secondary haemostasis?

Answer 32

OSPT and APTT

Question 33

How should you prepare the sample for secondary haemotasis test?

Answer 33

Non-clotted, citrate not EDTA

Question 34

Which pathways does whole blood clotting times evaulate?

Answer 34

Intrinsic and common

Question 35

Why is whole blood clotting time crude and insensitive?

Answer 35

Lots of other things influence, need adequate platelets to work

Question 36

How does drawing blood into glass tube activate clotting?

Answer 36

Has -ve charge

Question 37

How is activated clotting time more controlled than whole blood?

Answer 37

Temperature and diatomaceous earth for charge

Question 38

What is the problem with activated clotting time test?

Answer 38

Still needs platelets, insensitive

Question 39

Which pathways does APTT test?

Answer 39

Intrinsic and common

Question 40

What's an advantage of APTT test?

Answer 40

Doesn't need platelets (but still not sensitive)

Question 41

Above what % of reference control time is APTT abnormal?

Answer 41

20-25%

Question 42

Which pathways does OSPT activate?

Answer 42

Extrinsic and common

Question 43

WHat is the difference between OSPT and APTT?

Answer 43

OSPT provides TF as activator

Question 44

What test do you do if you suspect fibrinogen deficiency/dysfunction?

Answer 44

Thrombin clotting time

Question 45

How do you do the thrombin clotting time test?

Answer 45

Add thrombin to patients plasma to convert fibrinogen to fibrin

Question 46

How do you detect FDPs?

Answer 46

Latex agglutination

Question 47

What levels are FDPs normally?

Answer 47

Lowe

Question 48

Under what conditions are FDPs high?

Answer 48

With fibrinolysis e.g. DIC, iliac thrombosis, internal haemorrhage

Question 49

Why are FDP levels influenced by liver or kidney dysfunction?

Answer 49

This is how they are normally removed

Question 50

In what condition are D-dimers high?

Answer 50

DIC

Question 51

In what condition are D-dimers midrange?

Answer 51

Non-specific e.g. neoplasia, inflammation

Question 52

What are D-dimers produced from?

Answer 52

Cross-linked fibrin

Question 53

What does TEG test evaulate?

Answer 53

Clot formation and breakdown (clotting time and size)

Question 54

What does TEG assess that other tests can't?

Answer 54

Hypercoagulability and hyperfibrinolysis