Platelets

Question 1

How does EDTA affect clotting?

Answer 1

Cheylates Calcium altering platelet activation

Question 2

What is secreted from platelets that attracts more platelets?

Answer 2

von Willebrand Factor

Question 3

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

Answer 3

7-10 PLTs per hpf

Horses - 4-7

Question 4

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

Answer 4

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

Question 5

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

Answer 5

Blood smear, hematology analyzers

Question 6

Modified-live vaccination can cause what?

When would we see this?

What should we avoid if possible?

Answer 6

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

Question 7

What is considered normal clotting time for BMBT?

Answer 7

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

Question 8

What is the main thing that happens during secondary hemostasis?

Answer 8

Deposition of fibrin

Question 9

Is calcium required for platelet aggregation?

Answer 9

Yes dummy that’s why EDTA fucks with it

Question 10

True or false:

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

Answer 10

True

Question 11

What happens to a platelet when it changes shape?

What is the stimulation for PLT shape change?

Answer 11

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

Occurs in response to thrombin

Question 12

True or false:

Platelet aggregation is a reversible process.

Answer 12

False it is irreversible

Question 13

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

Answer 13

Cats

Question 14

What are three platelet related causes of hemorrhage?

Answer 14

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

Question 15

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

Answer 15

Yes, size always matters…

Question 16

What level of thrombocytopenia would be seen with hemorrhage?

Answer 16

Typically none, maybe mild if hemorrhage is acute and severe

Question 17

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

Answer 17

Platelet plug formation
Coagulation
Fibrinolysis

Question 18

Formation of primary hemostatic plug takes how long?

How does this happen?

Answer 18

~3-5 minutes

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

Question 19

What are the 6 mechanisms of thrombocytopenia?

Answer 19

Decreased Production
Destruction
Sequestration
Loss
Consumption
Pseudothrombocytopenia

Question 20

What are the two causes of increased thrombus formation?

What is the pathology of this?

Where does this most commonly occur

Answer 20

Increased procoagulant activity
Decreased fibrinolysis

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

Microvasculature

Question 21

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

Answer 21

CATS

Question 22

What is platelet consumption?

Answer 22

Utilization of platelets during coagulation

Question 23

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?

Answer 23

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

Question 24

What is a primary neoplasm that can affect platelet production?

Answer 24

Leukemia

Question 25

Bleeding time tests will be abnormal when?

Answer 25

Decreased platelet function and/or Decreased platelet numbers

Question 26

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

Answer 26

Increased MPV

Question 27

How do you differentiate megakaryocytes microscopically? What is a polyploid nucleus?

Answer 27

Large cells with abundant cytoplasm that have polyploid nucleus Many copies of cellular DNA

Question 28

What is the purpose of bleeding time tests? What does it NOT test?

Answer 28

Test the ability of PLTs to form platelet plug Does not test ability to make fibrin plug

Question 29

What does an increased MPV suggest?

Answer 29

Increased thrompoiesis

Question 30

What are causes of a reactive thrombocytosis?

Answer 30

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

Question 31

What characteristics of platelets might alter the hematology analyzer count?

Answer 31

Macroplatelets or platelet clumping

Question 32

True or false: | Thrombocytopenia is a specific disease.

Answer 32

False it is a diagnostic problem

Question 33

What are causes of pseudothrombocytopenia?

Answer 33

Macrothrombosis or platelet clumping

Question 34

What are two processes resulting in platelet destruction?

Answer 34

Immune-mediated thrombocytopenia (ITP) | Alloimmune thrombocytopenia

Question 35

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)

Answer 35

<30,000 / ul

Question 36

What are 3 possible causes of decreased thrombocyte production?

Answer 36

Neoplasia Necrosis or fibrosis of bone marrow Bone marrow hypoplasia

Question 37

Define hemostasis

Answer 37

Stoppage of blood

Question 38

Do you typically see primary or secondary thrombocytosis?

Answer 38

Secondary | Primary is a unicorn diagnosis

Question 39

When will you see a rebound thrombocytosis?

Answer 39

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

Question 40

The spleen retains what quantity of platelets in normal patients?

Answer 40

1/3 of the platelets in the body

Question 41

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

Answer 41

4-5 days

Question 42

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

Answer 42

Mild to moderate

Question 43

What are the three steps of platelet activation?

Answer 43

Shape change Flip of PLT membranes Secretion of granule products

Question 44

Will you see megakaryocytes in peripheral blood?

Answer 44

No, only on BMAs

Question 45

Where is thrombopoietin (TPO) continually produced? | What does TPO bind to?

Answer 45

Liver, kidney, muscle | Receptors on platelets

Question 46

What is attracted to the cell by flipping the membrane?

Answer 46

Calcium

Question 47

What are the tests utilized to determine platelet function?

Answer 47

Bleeding time tests | Specific platelet function tests (TEG and Platelet mapping)

Question 48

What is the approximate lifespan of a platelet?

Answer 48

5-10 days (shorter in cats)

Question 49

Can a BMBT differentiate between Thrombocytopenia an thrombocytopathy?

Answer 49

No, no it can't

Question 50

Which step of primary hemostasis requires von Willebrand Factor? What does vWF bind to on the platelet? What is the primary function of vWF?

Answer 50

Adhesion GP1b Bridge between PLTs and collagen

Question 51

True or false: | The degree of thrombocytopenia depends on the extent of bone marrow disease

Answer 51

True

Question 52

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

Answer 52

Active production of platelets

Question 53

What are the three steps of primary hemostasis?

Answer 53

Adehere Activation Aggregation

Question 54

How do you differentiate macroplatelets microscopically?

Answer 54

They are as large as (or larger than) RBCs

Question 55

What is the order of events in platelet plug formation?

Answer 55

Adhesion --> Activation --> Aggregation

Question 56

What is the test for platelet production?

Answer 56

Bone marrow aspirate

Question 57

True or false: | Animals with thrombocytosis are usually clinical in presentation.

Answer 57

False, they are usually asymptomatic

Question 58

When would we see sequestration of platelets?

Answer 58

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

Question 59

What is the cause of alloimune thrombocytopenia? Who does this affect

Answer 59

Dam produces antiplatelet antibody from a previous pregnancy | Foals and piglets (mainly piglets)

Question 60

What would be seen on CBC with ITP? PT/PTT? What would we see on BMA?

Answer 60

Severe thrombocytopenia +/- acute hemorrhagic anemia +/- leukocytosis PT/PTT - Normal Increased megakaryocytes

Question 61

True or false: | Piglets with alloimmune thrombocytopenia develop fine

Answer 61

False! | High mortality rate from hemorrhage in piglets

Question 62

What are the acquired causes of qualitative plt disorders?

Answer 62

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

Question 63

What things suggest PLT regeneration?

Answer 63

Macroplatelets on smear Increased MPV Increased megakaryocytes on BMA

Question 64

What are characteristics of a platelet-associated bleeding pattern?

Answer 64

``` Mucosal bleeding Petechiation Ecchymosis Spontaneous hemorrhage +/- hemorrhagic anemia ```

Question 65

When will you see thrombocytosis in horses?

Answer 65

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

Question 66

Which type of vWF is a quantitative deficiency? Which is more severe?

Answer 66

Types 1 and 3 Type 3

Question 67

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

Answer 67

von Willebrand's disease

Question 68

Where is vWF stored?

Answer 68

Weibel-Palade bodies | Probably no important but that's a funny name

Question 69

What is a consequence of vWD?

Answer 69

Decreased platelet adhesion

Question 70

What are the two primary functions of vWF?

Answer 70

Platelet adhesion | Factor VIII carrier