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Small Animal Medicine > Hematology - Hemostasis 1 > Flashcards

Hematology - Hemostasis 1 Flashcards

1
Q

What are the stages of hemostasis?

A

Primary, secondary, and tertiary hemostasis

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2
Q

What occurs during primary hemostasis?

A

The formation of the platelet plug

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3
Q

What is primary hemostasis sufficient for?

A

small vessel injury

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4
Q

What occurs during secondary hemostasis?

A

The formation of the fibrin clot through the coagulation cascade

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5
Q

What is secondary hemostasis needed for?

A

medium/large vessel injury

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6
Q

What occurs during tertiary hemostasis?

A

Fibrinolysis to re-establish blood flow through vessels

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7
Q

What clinical signs are associated with primary hemostatic defects?

A

Mucosal surface bleeding: petechiae, ecchymoses, epistaxis, hemoptysis, hematuria, hematemesis, melena, hematochezia, ocular bleeding, and CNS bleeding

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8
Q

What are the key cellular players in primary hemostasis?

A

endothelial cells and platelets

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9
Q

What are the key protein adhesive agents in primary hemostasis?

A

Von Willebrand factor (vWF), collagen, and fibrinogen

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10
Q

What are the key protein agonist agents in primary hemostasis?

A

ADP, thromboxane A2 (TXA2), and thrombin

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11
Q

What prevents platelet adhesion in the normal vessel?

A

Negatively charged endothelium, NO, prostacyclin, and ADPase

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12
Q

When subendothelium is exposed, what occurs during primary hemostasis?

A

von Willebrand facort binds to the subendothelium, a platelet enzyme binds to the subendothelial vWF, and the aggregation receptor becomes activated. Then another receptor binds to fibrinogen and in simple terms, more platelets are recruited and aggregate.

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13
Q

How do activated platelets set stage for secondary hemostasis?

A

Activated platelets flip their membranes which exposes phosphatidylserine and then provide a docking site for clotting factors needed in secondary hemostasis

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14
Q

Generally, what can go wrong with primary hemostasis?

A

Low platelet number, impaired platelet function, deficient vWF number, impaired vWF function

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15
Q

What is the most common acquired disorder of primary hemostasis?

A

thrombocytopenia

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16
Q

What can cause thrombocytopenia?

A

Use, destruction, and decreased production

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17
Q

What inherited disorder can lead to thrombocytopenia?

A

Congenital macrothrombocytopenia

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18
Q

What breeds is congenital macrothrombocytopenia common in?

A

Cavalier King Charles Spaniels, Norfold Terriers, and others

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19
Q

What occurs in congenital macrothrombocytopenia?

A

The patients don’t bleed because their platelets are too big

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20
Q

What are common acuired causes of thrombocytopenia?

A

Immune-mediated, infectious disease, DIC, and drugs

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21
Q

What is thrombopathia?

A

platelet dysfunction

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22
Q

What are the forms of thrombopathia?

A

inherited and acquired

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23
Q

What are the acquired causes of thrombopathia?

A

DIC, renal and liver disease, and drugs

24
Q

What is the most common inherited primary hemostatic disorder?

A

von Willebrand’s disease

25
Q

What breeds is vWD most common in?

A

Dobermans, German shorthaired pointers, scottish terriers, and many others

26
Q

If you suspect a hemostatic defect, what testing should be done?

A

Platelet count and coagulation profile

27
Q

How do you estimate the platelet count from a blood smear?

A

count in a 100x field - 1 per field equals 20,000 platelets/ul

28
Q

At what platelet count will spontaneous bleeding occur?

A

Less than 30,000

29
Q

How do you do vWD testing?

A

With vWF:Ag testing

30
Q

When should you perform vWD testing?

A

If the patient is of a predisposed breed, young, and previous bleeding

31
Q

How do you test platelet function?

A

Buccal mucosal bleeding time, platelet function analyzer, and specific platelet function tests

32
Q

What will cause BMBT to be abnormal (greater than 4 minutes)?

A

Thrombocytopenia, thrombopathic, vWF deficient/abnormal, and abnormal vasculature

33
Q

When should you do BMBT?

A

When other screening tests are normal - clotting times, platelet count, and >30% vWF:Ag

34
Q

Why is a platelet function analyzer not the best option?

A

Not all laboratories have them and they are not specific for which platelet defect

35
Q

What do specific platelet function tests require?

A

Specialized equipment and fresh platelets (in reference to their patient, not their blood)

36
Q

What are the generalized causes of thrombocytopenia?

A

Consumption of platelets, destruciton, decreased production, and sequestration

37
Q

When does appropriate consumption of platelets occur?

A

bleeding

38
Q

When does inappropriate consumption of platelets occur?

A

DIC

39
Q

True or false: Immune thrombocytopenia is a disorder that is of people and dogs. It is rare in cats.

A

TRUE

40
Q

What are the secondary causes of immune thrombocytopenia?

A

Drugs, infectious agents, and neoplasia

41
Q

What testing should be done to rule out secondary causes of ITP?

A

Tick panel, imaging, thorough drug history

42
Q

How is immune thrombocytopenia treated?

A

Immunosuppression just like for IMHA, glucocorticoids +/- a second agent

43
Q

What emergency measures can be taken to treat immune thrombocytopenia?

A

Vincristine and IVIG

44
Q

How does vincristine work?

A

It prevents microtubule polymerization and accelerated megakaryocyte fragmentation and platelet release from bone marrow

45
Q

Can vincristien be used to treat IMHA?

A

NO

46
Q

What does IVIG stand for?

A

Intravenous human immunoglobulin

47
Q

What does IVIG do?

A

It blocks mononuclear phagocyte Fc receptor so that macrophages cannot engulf Ab coated platelets and it reduces B cell antibody production

48
Q

What platelet transfusion products are preferred in primary hemostasis patients?

A

Fresh whole blood, platelet rich plasma, platelet rich concentrate, cryoplatelets, and lyophilized platelets

49
Q

What are cryoplatelets?

A

Platelet concentrate cryopreserved in DMSO

50
Q

What are the indications for platelet transfusions?

A

Severe thrombocytopenia, suspect pulmonary or CNS hemorrhage, and acquired or hereditary thromnopathias

51
Q

True or False: Plasma does not contain platelets.

A

TRUE

52
Q

What is the prognosis for immune thrombocytopenia?

A

Good - only a 10-30% mortality rare

53
Q

What are the natural inhibitors of primary hemostasis?

A

Endothelial cells as a physical barrier, ADPase, prostacyclin, and nitric oxide

54
Q

What are the pathological inhibitors of primary hemostasis?

A

Disease - DIC, metabolites in liver and kidney disease, and paraproteins

55
Q

What are the therapeutic inhibitors of primary hemostasis?

A

Platelet inhibitors - Aspirin, NSAIDS, and Clopidogrel

56
Q

What does Aspirin and NSAIDs do to inhibit platelets?

A

They are Cox inhibitors and TxA2 production inhibitors that don’t allow platelets to activate their neighbors

57
Q

How does Clopidogrel inhibit platelets?

A

It binds to their ADP receptor so that they cannot be activated

Small Animal Medicine (100 decks)

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