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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
How doe platelets help facilitate wound closure and vessel patency?
Clot reatraction via actinomyosin filaments
26
How do you determine PLT concentration in blood? (2 ways)
Blood smear | Hematology analyzers
27
How do you evaluate PLT morphology? (2 ways)
Blood smear | Hematology analyzers
28
How do you evaluate PLT function?
Bleeding time tests
29
How do you evaluate PLT production?
Bone marrow aspirate
30
How many PLTs should you have on a smear?
At least 7-10 PLTs/OIF (horses at least 4-7 PLTs/OIF)
31
What do you need to watch for when reading a smear for platelets?
Clumping, especially in cats and cattle
32
What ranges are given for mild, moderate and severe thrombocytopenia?
``` Mild = 80,000 - 150,000/uL Moderate = 30,000 - 80,000/uL Severe = <30,000/uL ```
33
What PLT number means spontaneous hemorrhage?
<20,000/uL
34
What is thrombocytosis?
PLT higher than reference interval
35
What species do you see more PLT size variation in?
Cats
36
What species has pale staining PLTs?
Horses
37
What does increased numbers of large PLTs suggest?
Active production of PLTs
38
What does increase MPV suggest with regards to platelets?
Thrombopoiesis
39
What is the purpose of a bleeding time test?
To test PLT function
40
What is the BMBT?
Buccal Mucosal Bleeding Time
41
What are normal BMBTs for dogs, cats and horses?
``` Dog = 1 - 5 min Cat = 1 - 3.5 min Horse = 8 - 10 min ```
42
How is the cuticle bleeding time test done?
Cut the apex of the quick with guillotine clippers and measure time for bleeding to stop.
43
What is the time for dogs to stop bleeding with the cuticle bleeding time test?
2-8 minutes
44
When would you do a bone marrow aspirate to look at platelets? (2 reasons)
When you see a pancytopenia | Low PLT numbers with no obvious reason.
45
What are 2 causes of low PLT numbers in the bone marrow?
Neoplasia | Crowding by other cells
46
T/F; Thrombocytopenia is a specific disease.
False. Thrombocytopenia is diagnostic problem
47
What are the 5 clinical features of thrombocytopenia?
``` Mucosal bleeding Petechiation Ecchymosis Spontaneous hemorrhage +/- Hemorrhagic anemia ```
48
What are the 4 main mechanisms of thrombocytopenia?
Production Consumption Sequestration Loss
49
T/F: Hemorrhage doesn't cause thrombocytopenia, but thrombocytopenia can cause hemorrhage.
True Exception is acute, severe hemorrhage may cause a mild thrombocytopenia.
50
What are 3 common causes of thrombocytopenia due to consumption?
DIC Vasculitis (rickettsials, FIP) Viral infection
51
What degree of thrombocytopenia do you see with consumption?
Mild to moderate
52
What is a major cause of thrombocytopenia due to destruction?
Immune mediated thrombocytopenia
53
What two species are susceptible to alloimmune thrombocytopenia?
Piglets | Foals
54
How can MLV vaccines result in thrombocytopenia?
Can induce immune response against the PLTs, which then aggregate and are cleared 3-10 days post-vaccination.
55
What degree of thrombocytopenia do you see in cases of PLT destruction?
Severe thrombocytopenia
56
What will you find in a CBC with thrombocytopenia due to destruction? (3 things)
Severe thrombocytopenia +/- acute hemorrhagic anemia +/- leukocytosis NOTE: (PT and PTT will be normal)
57
What will you find in a bone marrow aspirate with thrombocytopenia due to destruction?
Increased megakaryocytes
58
What will the results of anti-platelet antibody tests be with thrombocytopenia due to destruction?
Positive
59
What will serum biochemistry be with thrombocytopenia due to destruction?
Normal
60
What are 3 causes of decreased PLT production?
Bone marrow hypoplasia Neoplasia Myelonecrosis or myelofibrosis
61
Where might PLTs get sequestered?
In large vascular beds
62
What are 4 cases of PLT sequestration/abnormal distribution?
Splenomegaly, torsion, neoplasia Hepatomegaly, portal hypertension Vasodilation in endotoxic shock Severe hypothermia
63
When can you see a pseudothrombocytopenia? (2 things0
Analyzer can't measure because PLTs are to obig, or clumped
64
What are the two major mechanisms in thrombocytosis?
Increased production | Increased distribution
65
Are animals symptomatic with increased platelet count?
No
66
What is the primary cause of thrombocytosis?
Neoplastic production of PLTs
67
What is the secondary cause of thrombocytosis? (2 things)
Reactive thrombocytosis associated with some diseases. | Associated with certain situations
68
What is a major cause of reactive thrombocytosis?
Chronic inflammatory disease
69
What do you suspect in an animal with clinical signs of thrombocytopenia, but a normal platelet count?
Qualitative disorders
70
What are 4 acquired causes of qualitative platelet disorders?
Uremia Drugs Fibrin degradation products (FDPs) Paraproteins
71
What are 4 inherited causes of qualitative platelet disorders?
No glycoprotein receptors No or reduced granules Signal transduction defects vWF deficiency***
72
What is the main result of vWF deficiency?
Decreased platelet adhesion
73
What are the two forms of vonWillebrand Disease?
``` Quantitative deficiency (Type 1, Type 3) Qualitative deficiency (Type 2) ```
74
What is the severity of Type 1 von Willebrand Disease?
Mild, dogs usually subclinical
75
What is the severity of Type 3 von Willebrand Disease?
Severe
76
What is the main clinical feature with vWD?
Mild to severe bleeding
77
How is vWD diagnosed? (5 things)
Based on signalment, history, medications, other primary disorders, Platelet/Coagulation evaluation
78
What 3 diseases can cause thrombocytosis?
Chronic inflammatory disease Iron deficiency anemia IMHA
79
What are 3 situations that can cause thrombocytosis?
Post-splenectomy Excitement Response to drugs (Vincristine) Rebound from thrombocytopenia
80
What test can confirm vWD?
Run plasma vWD concentration

Clinical Pathology (9 decks)

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