Hemostatic Disorders

Question 1

What is primary hemostasis

Answer 1

Platelet plug formation

Question 2

Steps of primary hemostasis (3)

Answer 2

1) Platelets adhered to exposure vWF on subendothelial collagen
2) Platelets release ADP
3) Platelets aggregate - release factors for binding

Question 3

Receptors involved in platelet aggregation

Answer 3

GpIIa/IIIb or CD41/CD61

Question 4

What is an important co-factor in secondary hemostasis

Answer 4

CALCIUM

Question 5

What is secondary hemostasis

Answer 5

Fibrin clot formation

Question 6

What happens in extrinsic pathway

Answer 6

1) Tissue Factor released from damaged cells 2) TF binds with plasma factor VII –> TF-VIIa

Question 7

Factors in extrinsic pathway

Answer 7

TF and VII (Ca required)

Question 8

What happens in intrinsic pathway

Answer 8

1) Exposed collagen binds and activates plasma factor XII 2) XII activates enzymatic cascade leading to Prothrombin Activator Complex

Question 9

Which factors are involved in intrinsic pathway

Answer 9

XII, XI, IX, VIII

Question 10

Factors in common pathway

Answer 10

X, V, II, I, XIII

Question 11

Vitamin K factors

Answer 11

II, VII, IX, X

Question 12

Sources of vitamin K

Answer 12

Diet Bacteria

Question 13

Where is vitamin K needed as a co-factor

Answer 13

Liver

Question 14

Causes of hemorrhage: vessels

Answer 14

1) Rhexis (bursting)
2) Trauma, inflammation, infection, endotoxin, type III hypersensitivity, collagen disorders, vitamin C deficiency

Question 15

Causes of hemorrhage: platelets

Answer 15

1) Decreased production
2) Decreased function
3) Destruction (immune mediated thrombocytopenia - IMT)
4) Consumption (DIC)

Question 16

Causes of hemorrhage: coagulation factors

Answer 16

Inherited deficiencies Acquired defects

Question 17

Hemorrhage that is <3mm is

Answer 17

Petechial

Question 18

Hemorrhage >1cm is

Answer 18

Ecchymosis

Question 19

Petechial hemorrhage is caused by

Answer 19

Diapedesis

Question 20

Ecchymosis is caused by

Answer 20

Damage to capillary beds

Question 21

Inherited factor deficiencies (4)

Answer 21

II (Prothrombin) - affects dogs.

• Mild bleeding in adults
• Epitaxis and umbilicus bleed in puppies

VII - affects dogs

• Mild, more easily bruised

IX (hemophilia B) - affects dogs, cats, rarely horses

• Variable severity
• Severe in large dogs

X - affects cats and dogs

• Severe bleeding!

Question 22

Acquired coagulation factor defects

Answer 22

Decreased production due to:

1) Severe liver disease
2) Vit K deficiency (deficiency of II, VII, IX, X, proteins c and s)

Question 23

What causes acquired vit k deficiency

Answer 23

Moldy sweet clover

Warfarin

Sulaquinoxaline

Question 24

What binds a heparin-like molecule on platelets, and inhibits factors IIa, Xa, and IXa on active site

Answer 24

Antithrombin III

Question 25

What inactivates TF-VIIa complex of extrinsic pathway

Answer 25

TFPI

Question 26

What inhibits factors Va and VIIa

Answer 26

Protein C/S (activated by IIa)

Question 27

What do endothelial products inhibt

Answer 27

Platelets

Question 28

What does tissue plasminogen A do

Answer 28

Activates fibrinolysis

Question 29

List the antithrombotic mechanisms

Answer 29

1) Antithrombin III
2) TFPI
3) Protein C/S (vit K dependent)
4) Endothelial products
5) tpA

Question 30

Whats a persistent thrombus in vessel lumen called

Answer 30

Thromboembolus

Question 31

Whats a thrombus in the heart called

Answer 31

Mural thrombus

Question 32

Causes of thrombus formation (4)

Answer 32

1) Reduced blood flow (cardiac insufficiency, hypovolemia, obstructions)
2) Turblent blood flow
3) Hypercoagulability (production of procoagulations, DIC, inflammation)
4) Endothelial injury, activation

Question 33

A saddle embolism is a

Answer 33

Arterial thromboemboli

Question 34

What are arterial thromboemboli usually caused by

Answer 34

Aortic thrombi dislodging and settling at a birfucation downstream

Question 35

You find a pale, white emboli. Its likely a…

Answer 35

Arterial thromboemboli

Question 36

You find a thrombus that is dark red and gelatinous. It’s likely a…

Answer 36

Venous thrombus

Question 37

Venous thrombi formation

Answer 37

Blood stasis / slow blood flow They are large numbers of RBCs that are loosely incorporated due to slow blood flow

Question 38

Where are venous thrombi typically found

Answer 38

Pulmonary veins

Question 39

Which type of thrombi can result in pulmonary infarcts or right-sided heart failure

Answer 39

Venous thrombi

Question 40

Which type of thrombi is common in cats with cardiomyopathies

Answer 40

Arterial thromboemboli

Question 41

You see a thrombus that is yellow. What is it? Which part of the body are you likely in?

Answer 41

Postmortem thrombus Typically in heart, vessels

Question 42

Steps of thrombolysis

Answer 42

1) Plasminogen binds to clot
2) Tissue plasminogen activator released from endothelium or ECM and binds to clot
3) Plasminogen —> Plasmin
4) Plasmin degrades fibrin, fibrinogen, Va, VIIIa, vWF, HMWK
5) Clot dissolves, leaving fibrin degradation products

Question 43

How do larger, persistent thrombi dissolve? What can occur after?

Answer 43

By phagocytosis Granulation tissue forms after

Question 44

Mural/occlusive thrombi are dissolved how?

Answer 44

Invaded by FIBROBLASTS Recanalization: form new vascular channels, providing alternative blood through and around the thrombus

Question 45

What are the risks of recanalization

Answer 45

Increased blood turbulence at site of mural thrombus —> risk of more thrombi!

Question 46

3 ways to remove a thrombus

Answer 46

1) Thombolysis
2) Phagocytosis
3) Fibroblast/recanalization