Primary Hemostasis

What is hemostasis?

an intricate, highly balanced interaction between blood vessels, platelets, and soluble factors that are involved in the formation and dissolution of blood clots

How long does it take from initial formation to release of platelets?

4-5 days

What is the main growth factor for platelets?

Thrombopoietin (TPO)

True or False: The spleen contains 30-40% of circulating mass at any time.

TRUE

What species have thrombocytes?

Reptiles, amphibians, fish, and birds

What is unique about thrombocytes?

nucleated and phagocytic

What activates the platelet?

subendothelial collagen to repair the endothelium

For measuring platelets, what kind of tube should you use?

EDTA (purple)

What is the ability to clot based on?

Mass - not platelet number

Where do you look on a smear to find platelets?

feathered edge

How many platelets should you see per FOV at 100x?

10-15

How do you estimate platelets?

average PLT per 100x FOV x 15,000

What are the four categories of thrombocytopenia?

• destruction

• Consumption

• Lack of production

• Redistribution

What can cause destruction thrombocytopenia?

• Immune mediated

  • Drug reactions

  • Autoimmune disease

• Infections

  • Ehrlichiosis

  • Rocky Mountain Spotted Fever

WHat can cause consumption thrombocytopenia?

DIC ((disseminated intravascular coagulopathy)

• coag cascade is unrestrained

What can cause decreased production thrombocytopenia?

• Myelophthisis (bone marrow failure when replaced by abnormal tissue)

• Aplastic anemia (pancytopenia)

  • Drug reactions

  • Estrogen

  • Idiopathic

True or False: Redistribution thrombocytopenia is common.

FALSE

Where are thrombocytes sequestered in redistribution thrombocytopenia?

Spleen

What is the clinical presentation of thrombocytopenia?

Most cause petechiae and frank bleeding

True or False: Redistribution thrombocytopenia shows clinical signs

FALSE

Which forms of thrombocytopenia have an increased MPV?

• destruction

• Consumption

What forms of thrombocytopenia have a decreased MPV?

decreased production

What forms of thrombocytopenia have a normal MPV?

redistribution

In the bone marrow, which forms of thrombocytopenia have increased megakaryocytes?

• destruction

• Consumption

In the bone marrow, which forms of thrombocytopenia have a decreased megakaryocytes?

Decreased production

True or False: Thrombocytosis is common and often does not carry clinical significance.

TRUE

What can cause a thrombocyosis?

• excitement

• Chronic bleeding

• Iron deficiency

• Inflammation

• MK neoplasia

What is an inherited disease where the platelets do not work?

von Willebrand’s disease

What are some acquired diseases where latelets do not work?

• uremia

• Drugs

• Multiple myeloma

Where is Von vwillebrands factor found?

plasma and subendothelium

What does vWF do?

• promotes platelet to platelet adhesion

• Facilitates platelet adhesion to subendothelial collagen

• Allows endothelial cells to regrow

What is Von Willebrands disease?

Inherited disordered where there is a deficiency of vWF and platelets do not adhere to the subendothelium

How do we assess platelet function?

BMBT (buccal mucosal bleeding time)

How long is the lancet in a BMBT test?

5mm long and 1mm deep

What is normal BMBT in an anesthetized dog?

<4min

What is a normal BMBT in an anesthetized cat?

<3.3 min