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Clinical Pathology > Hemostasis and Platelet Disorders > Flashcards

Hemostasis and Platelet Disorders Flashcards

1
Q

What is hemostasis?

A

Stopping blood

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2
Q

What is the goal of hemostasis?

A

To sop blood without obstructing blood flow

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3
Q

Injury to a vessel causes these three steps.

A

Vessel constriction
Platelet adhesion
Activation of coagulation

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4
Q

What is blanaced hemostasis?

A

Balance between thrombosis and hemorrhage

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5
Q

How much of the platelet mass is in the spleen?

A

1/3

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6
Q

What does the presence of large and giant platelets suggest?

A

Increased platelet production

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7
Q

Where do you find megakaryocytes?

A

In the sinus in bone

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8
Q

How long does it take to go from megakaryoblast to platelet release?

A

4-5 days

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9
Q

How do platelets get into circulation?

A

Proplatelet processes extend into the sinus lumen and break into individual platelets

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10
Q

What substance regulates platelet production?

A

Thrombopoietin (TPO)

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11
Q

Where in TPO continually produced? (3 places)

A

Liver
Basement membrane
Endothelium

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12
Q

How does TPO work?

A

It binds to platelets. The less platelets, the more free plasma TPO which stimulates thrombopoiesis.

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13
Q

Will EPO stimulate thrombopoiesis?

A

Yes

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14
Q

What is the lifespan of a platelet?

A

~5-10 days (shorter in cats)

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15
Q

What are the two main functions of platelets?

A

Primary hemostasis

Support secondary hemostasis

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16
Q

What is primary hemostasis?

A

Formation of the primary hemostatic plug

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17
Q

How long does primary hemostasis take?

A

3-5 minutes

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18
Q

What does primary hemostasis entail?

A

PLTs adhere to the subendothelium, activate, secrete granules and aggregate to form a plug.

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19
Q

What 4 things does PLT adhesion require?

A

vonWillebrand Factor
ADP
Ca2+
Serotonin

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20
Q

What does PLT activation entail?

A

Shape change from smooth disc to spheres with many filapodia in response to thrombin.

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21
Q

During PLT activation, what doe the PLTs secrete from their granules?

A

Factors V and VIII
Thromboxane A2
Ca2+

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22
Q

What are the 4 functions of the platelet granule products?

A

Recruit more PLTs
Further PLT activation
Facilitate coagulation
Mediate vessel repair

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23
Q

Why is Calcium required for platelet aggregation?

A

Because the Ca2+ gives the activated PLTs a positive charge, which attracts more platelets which initially have a negative charge.

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24
Q

What do PLTs provide a surface for?

A

Formation and deposition of fibrin

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25
Q

How doe platelets help facilitate wound closure and vessel patency?

A

Clot reatraction via actinomyosin filaments

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26
Q

How do you determine PLT concentration in blood? (2 ways)

A

Blood smear

Hematology analyzers

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27
Q

How do you evaluate PLT morphology? (2 ways)

A

Blood smear

Hematology analyzers

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28
Q

How do you evaluate PLT function?

A

Bleeding time tests

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29
Q

How do you evaluate PLT production?

A

Bone marrow aspirate

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30
Q

How many PLTs should you have on a smear?

A

At least 7-10 PLTs/OIF (horses at least 4-7 PLTs/OIF)

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31
Q

What do you need to watch for when reading a smear for platelets?

A

Clumping, especially in cats and cattle

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32
Q

What ranges are given for mild, moderate and severe thrombocytopenia?

A 
Mild = 80,000 - 150,000/uL
Moderate = 30,000 - 80,000/uL
Severe = <30,000/uL
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33
Q

What PLT number means spontaneous hemorrhage?

A

<20,000/uL

34
Q

What is thrombocytosis?

A

PLT higher than reference interval

35
Q

What species do you see more PLT size variation in?

A

Cats

36
Q

What species has pale staining PLTs?

A

Horses

37
Q

What does increased numbers of large PLTs suggest?

A

Active production of PLTs

38
Q

What does increase MPV suggest with regards to platelets?

A

Thrombopoiesis

39
Q

What is the purpose of a bleeding time test?

A

To test PLT function

40
Q

What is the BMBT?

A

Buccal Mucosal Bleeding Time

41
Q

What are normal BMBTs for dogs, cats and horses?

A 
Dog = 1 - 5 min
Cat = 1 - 3.5 min
Horse = 8 - 10 min
42
Q

How is the cuticle bleeding time test done?

A

Cut the apex of the quick with guillotine clippers and measure time for bleeding to stop.

43
Q

What is the time for dogs to stop bleeding with the cuticle bleeding time test?

A

2-8 minutes

44
Q

When would you do a bone marrow aspirate to look at platelets? (2 reasons)

A

When you see a pancytopenia

Low PLT numbers with no obvious reason.

45
Q

What are 2 causes of low PLT numbers in the bone marrow?

A

Neoplasia

Crowding by other cells

46
Q

T/F; Thrombocytopenia is a specific disease.

A

False. Thrombocytopenia is diagnostic problem

47
Q

What are the 5 clinical features of thrombocytopenia?

A 
Mucosal bleeding
Petechiation
Ecchymosis
Spontaneous hemorrhage
\+/- Hemorrhagic anemia
48
Q

What are the 4 main mechanisms of thrombocytopenia?

A

Production
Consumption
Sequestration
Loss

49
Q

T/F: Hemorrhage doesn’t cause thrombocytopenia, but thrombocytopenia can cause hemorrhage.

A

True

Exception is acute, severe hemorrhage may cause a mild thrombocytopenia.

50
Q

What are 3 common causes of thrombocytopenia due to consumption?

A

DIC
Vasculitis (rickettsials, FIP)
Viral infection

51
Q

What degree of thrombocytopenia do you see with consumption?

A

Mild to moderate

52
Q

What is a major cause of thrombocytopenia due to destruction?

A

Immune mediated thrombocytopenia

53
Q

What two species are susceptible to alloimmune thrombocytopenia?

A

Piglets

Foals

54
Q

How can MLV vaccines result in thrombocytopenia?

A

Can induce immune response against the PLTs, which then aggregate and are cleared 3-10 days post-vaccination.

55
Q

What degree of thrombocytopenia do you see in cases of PLT destruction?

A

Severe thrombocytopenia

56
Q

What will you find in a CBC with thrombocytopenia due to destruction? (3 things)

A

Severe thrombocytopenia
+/- acute hemorrhagic anemia
+/- leukocytosis

NOTE: (PT and PTT will be normal)

57
Q

What will you find in a bone marrow aspirate with thrombocytopenia due to destruction?

A

Increased megakaryocytes

58
Q

What will the results of anti-platelet antibody tests be with thrombocytopenia due to destruction?

A

Positive

59
Q

What will serum biochemistry be with thrombocytopenia due to destruction?

A

Normal

60
Q

What are 3 causes of decreased PLT production?

A

Bone marrow hypoplasia
Neoplasia
Myelonecrosis or myelofibrosis

61
Q

Where might PLTs get sequestered?

A

In large vascular beds

62
Q

What are 4 cases of PLT sequestration/abnormal distribution?

A

Splenomegaly, torsion, neoplasia
Hepatomegaly, portal hypertension
Vasodilation in endotoxic shock
Severe hypothermia

63
Q

When can you see a pseudothrombocytopenia? (2 things0

A

Analyzer can’t measure because PLTs are to obig, or clumped

64
Q

What are the two major mechanisms in thrombocytosis?

A

Increased production

Increased distribution

65
Q

Are animals symptomatic with increased platelet count?

A

No

66
Q

What is the primary cause of thrombocytosis?

A

Neoplastic production of PLTs

67
Q

What is the secondary cause of thrombocytosis? (2 things)

A

Reactive thrombocytosis associated with some diseases.

Associated with certain situations

68
Q

What is a major cause of reactive thrombocytosis?

A

Chronic inflammatory disease

69
Q

What do you suspect in an animal with clinical signs of thrombocytopenia, but a normal platelet count?

A

Qualitative disorders

70
Q

What are 4 acquired causes of qualitative platelet disorders?

A

Uremia
Drugs
Fibrin degradation products (FDPs)
Paraproteins

71
Q

What are 4 inherited causes of qualitative platelet disorders?

A

No glycoprotein receptors
No or reduced granules
Signal transduction defects
vWF deficiency***

72
Q

What is the main result of vWF deficiency?

A

Decreased platelet adhesion

73
Q

What are the two forms of vonWillebrand Disease?

A 
Quantitative deficiency (Type 1, Type 3)
Qualitative deficiency (Type 2)
74
Q

What is the severity of Type 1 von Willebrand Disease?

A

Mild, dogs usually subclinical

75
Q

What is the severity of Type 3 von Willebrand Disease?

A

Severe

76
Q

What is the main clinical feature with vWD?

A

Mild to severe bleeding

77
Q

How is vWD diagnosed? (5 things)

A

Based on signalment, history, medications, other primary disorders, Platelet/Coagulation evaluation

78
Q

What 3 diseases can cause thrombocytosis?

A

Chronic inflammatory disease
Iron deficiency anemia
IMHA

79
Q

What are 3 situations that can cause thrombocytosis?

A

Post-splenectomy
Excitement
Response to drugs (Vincristine)
Rebound from thrombocytopenia

80
Q

What test can confirm vWD?

A

Run plasma vWD concentration

Clinical Pathology (9 decks)

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