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Ross Clin. Path. > Platelets > Flashcards

Platelets Flashcards

1
Q

How does EDTA affect clotting?

A

Cheylates Calcium altering platelet activation

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2
Q

What is secreted from platelets that attracts more platelets?

A

von Willebrand Factor

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3
Q

What is an appropriate estimate of PLT concentration on blood smears?

A

7-10 PLTs per hpf

Horses - 4-7

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4
Q

What are some of the granular products secreted during platelet activation?

A

ADP, Factors 5 and 8, thromboxane A2, calcium, vWF

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5
Q

What are the laboratory tests utilized to determine platelet concentration and morphology?

A

Blood smear, hematology analyzers

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6
Q

Modified-live vaccination can cause what?

When would we see this?

What should we avoid if possible?

A

May induce an immune response against PLTs leading to aggregation and clearance
If this happens it is 3-10 days post vaccination
Avoid surgery during this post vaccination period

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7
Q

What is considered normal clotting time for BMBT?

A

Depends on species
Dogs - 2-4 minutes
Cats - 1-3 minutes
Horses and cattle - 8-10 minutes

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8
Q

What is the main thing that happens during secondary hemostasis?

A

Deposition of fibrin

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9
Q

Is calcium required for platelet aggregation?

A

Yes dummy that’s why EDTA fucks with it

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10
Q

True or false:

Patients with vWD will have normal platelet counts and a prolonged BMBT

A

True

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11
Q

What happens to a platelet when it changes shape?

What is the stimulation for PLT shape change?

A

Shift from smooth discs to spheres with many filopodia increasing surface area

Occurs in response to thrombin

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12
Q

True or false:

Platelet aggregation is a reversible process.

A

False it is irreversible

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13
Q

In which species will you see more variation of platelet size normally?

A

Cats

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14
Q

What are three platelet related causes of hemorrhage?

A

Decreased platelet number or loss of platelet function
Decreased coagulation factor number or loss of factor function
Increased fibrinolysis

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15
Q

When performing a BMBT does the size of your incision make a difference?

A

Yes, size always matters…

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16
Q

What level of thrombocytopenia would be seen with hemorrhage?

A

Typically none, maybe mild if hemorrhage is acute and severe

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17
Q

What are the 3 phases of vessel injury repair utilizing platelets?

A

Platelet plug formation
Coagulation
Fibrinolysis

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18
Q

Formation of primary hemostatic plug takes how long?

How does this happen?

A

~3-5 minutes

Platelets adhere to subendothelium
Undergo activation
Aggregate to form a platelet plug

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19
Q

What are the 6 mechanisms of thrombocytopenia?

A 
Decreased Production
Destruction
Sequestration
Loss
Consumption
Pseudothrombocytopenia
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20
Q

What are the two causes of increased thrombus formation?

What is the pathology of this?

Where does this most commonly occur

A

Increased procoagulant activity
Decreased fibrinolysis

Excessive thrombus formation –> obstructed blood flow –> local hypoxia

Microvasculature

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21
Q

In what species are you especially concerned with and check for platelet clumping?

A

CATS

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22
Q

What is platelet consumption?

A

Utilization of platelets during coagulation

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23
Q

What will you see with decreased platelet numbers in regards to TPO?
What is a consequence of this?
With increased BM stimulation what will be seen?

A

Increased TPO free in plasma.
Increased bone marrow stimulation
Increased number, size, and ploidy of megakaryocytes with decreased maturation time

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24
Q

What is a primary neoplasm that can affect platelet production?

A

Leukemia

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25
Q

Bleeding time tests will be abnormal when?

A

Decreased platelet function
and/or
Decreased platelet numbers

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26
Q

If a macrothrombocytosis is seen on blood smear what hematology analyzer finding would you expect to see?

A

Increased MPV

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27
Q

How do you differentiate megakaryocytes microscopically?

What is a polyploid nucleus?

A

Large cells with abundant cytoplasm that have polyploid nucleus

Many copies of cellular DNA

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28
Q

What is the purpose of bleeding time tests?

What does it NOT test?

A

Test the ability of PLTs to form platelet plug

Does not test ability to make fibrin plug

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29
Q

What does an increased MPV suggest?

A

Increased thrompoiesis

30
Q

What are causes of a reactive thrombocytosis?

A 
Underlying disease:
Neoplasia
Inflammation (immune-mediated)
Endocrine disease (esp. cushings)
Regenerative anemias
31
Q

What characteristics of platelets might alter the hematology analyzer count?

A

Macroplatelets or platelet clumping

32
Q

True or false:

Thrombocytopenia is a specific disease.

A

False it is a diagnostic problem

33
Q

What are causes of pseudothrombocytopenia?

A

Macrothrombosis or platelet clumping

34
Q

What are two processes resulting in platelet destruction?

A

Immune-mediated thrombocytopenia (ITP)

Alloimmune thrombocytopenia

35
Q

Patients are at risk for spontaneous hemorrhage when the platelet count is what?
(THIS IS SAMPLE NOT THRALL, YES THEY HAVE DIFFERENT OPINIONS ON THIS)

A

<30,000 / ul

36
Q

What are 3 possible causes of decreased thrombocyte production?

A

Neoplasia
Necrosis or fibrosis of bone marrow
Bone marrow hypoplasia

37
Q

Define hemostasis

A

Stoppage of blood

38
Q

Do you typically see primary or secondary thrombocytosis?

A

Secondary

Primary is a unicorn diagnosis

39
Q

When will you see a rebound thrombocytosis?

A

Following acute plt loss:
Post splenectomy
Managed (treated) ITP

40
Q

The spleen retains what quantity of platelets in normal patients?

A

1/3 of the platelets in the body

41
Q

How long does a platelet take to mature from a megakaryocyte?

A

4-5 days

42
Q

What level of thrombocytopenia would be seen in a sequestration disorder?

A

Mild to moderate

43
Q

What are the three steps of platelet activation?

A

Shape change
Flip of PLT membranes
Secretion of granule products

44
Q

Will you see megakaryocytes in peripheral blood?

A

No, only on BMAs

45
Q

Where is thrombopoietin (TPO) continually produced?

What does TPO bind to?

A

Liver, kidney, muscle

Receptors on platelets

46
Q

What is attracted to the cell by flipping the membrane?

A

Calcium

47
Q

What are the tests utilized to determine platelet function?

A

Bleeding time tests

Specific platelet function tests (TEG and Platelet mapping)

48
Q

What is the approximate lifespan of a platelet?

A

5-10 days (shorter in cats)

49
Q

Can a BMBT differentiate between Thrombocytopenia an thrombocytopathy?

A

No, no it can’t

50
Q

Which step of primary hemostasis requires von Willebrand Factor?

What does vWF bind to on the platelet?

What is the primary function of vWF?

A

Adhesion

GP1b

Bridge between PLTs and collagen

51
Q

True or false:

The degree of thrombocytopenia depends on the extent of bone marrow disease

A

True

52
Q

You see an increased number of enlarged PLTs on a smear, what is this suggestive of?

A

Active production of platelets

53
Q

What are the three steps of primary hemostasis?

A

Adehere
Activation
Aggregation

54
Q

How do you differentiate macroplatelets microscopically?

A

They are as large as (or larger than) RBCs

55
Q

What is the order of events in platelet plug formation?

A

Adhesion –> Activation –> Aggregation

56
Q

What is the test for platelet production?

A

Bone marrow aspirate

57
Q

True or false:

Animals with thrombocytosis are usually clinical in presentation.

A

False, they are usually asymptomatic

58
Q

When would we see sequestration of platelets?

A

Splenomegaly, splenic torsion, neoplasia, portal hypertension, vasodilation in endotoxic shock, severe hypothermia

59
Q

What is the cause of alloimune thrombocytopenia?

Who does this affect

A

Dam produces antiplatelet antibody from a previous pregnancy

Foals and piglets (mainly piglets)

60
Q

What would be seen on CBC with ITP?

PT/PTT?

What would we see on BMA?

A

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

PT/PTT - Normal

Increased megakaryocytes

61
Q

True or false:

Piglets with alloimmune thrombocytopenia develop fine

A

False!

High mortality rate from hemorrhage in piglets

62
Q

What are the acquired causes of qualitative plt disorders?

A

Uremia
Drugs - NSAIDs, Calcium channel blockers
Fibrin Degredation Products (DIC)
Paraproteins

63
Q

What things suggest PLT regeneration?

A

Macroplatelets on smear
Increased MPV
Increased megakaryocytes on BMA

64
Q

What are characteristics of a platelet-associated bleeding pattern?

A 
Mucosal bleeding
Petechiation
Ecchymosis
Spontaneous hemorrhage
\+/- hemorrhagic anemia
65
Q

When will you see thrombocytosis in horses?

A

Splenic contraction

That shit is muscular as hell and gets contracted frequently after exercise

66
Q

Which type of vWF is a quantitative deficiency?

Which is more severe?

A

Types 1 and 3

Type 3

67
Q

What is the inherited plt disorder we are most concerned with?

A

von Willebrand’s disease

68
Q

Where is vWF stored?

A

Weibel-Palade bodies

Probably no important but that’s a funny name

69
Q

What is a consequence of vWD?

A

Decreased platelet adhesion

70
Q

What are the two primary functions of vWF?

A

Platelet adhesion

Factor VIII carrier

Ross Clin. Path. (3 decks)

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