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Blood and Lymph Unit 3 > Hemostasis: Approach to a Patient > Flashcards

Hemostasis: Approach to a Patient Flashcards

1
Q

What cell is described as small anuclear discoid or 2-3 microns and is derived from megakaryocytes?

A

Platelets

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2
Q

How long does it take for a platelet to mature?

How long is the lifespan of a platelet?

A
  • 4-5 days

- 9-10 days

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3
Q

What percentage of platelets are found in circulation?

In the spleen?

A

80% in circulation

20% in spleen

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4
Q

What are megathrombocytes?

A

Newly formed platelets that are large in size

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5
Q

Platelets contain ____________ but do not contain ____________

A

Mitochondria

Nuclei

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6
Q

What are the three kinds of functional granules found in a platelet?

A

Dense
Alpha
Lysosomal granules

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7
Q

What do dense granules contain?

A

ATP
ADP
Serotonin
Calcium

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8
Q

What do alpha-granules contain?

A

A number of proteins essential for platelet funciton including procoagulant proteins, plaelet-specific factors for platelet activation, and growth favtors

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9
Q

What do lysosomal granules contain?

A

Acid hydrolases

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10
Q

What is the function of surface-connected canalicular systems?

A

These extensive systems of internal membrane tunnels are tunnels through which the contents of the platelet granules are extruded during platelet aggregation and secretion

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11
Q

What are the main functions of platelets?

A

Adhesion to the vascular subendothelium at sites of injury

Activation of intracellular signaling pathways leading to cytoskeletal changes and release of intracellular gransules

Aggregation to form the platelet plug

Support thrombin generation

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12
Q

Intact endothelial cells can produce what two compounds that act as inhibitors of platelet activation?

A

Nitric oxide and prostacyclin

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13
Q

What factor do platelets bind in order to adhere to injured endothelium?

A

von Willebrand’s Factor

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14
Q

What protein is used to link vWF to platelets?

A

GP1b

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15
Q

What is the role of GPIIb-IIIa in platelet and vWF adhesion?

A

The enzyme increases its affinity

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16
Q

What happens after platelets adhere to the injured vessel wall?

A

They undergo a shape change through cytoskeletal activation, becoming more spherical with extended pseudpods and spread over the exposed subendothelium

Then they release the granules

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17
Q

Platelets adhere to each other through which protein?

A

Fibrinogen is a cross-linker between GPIIb-IIIa

18
Q

What converts fibrinogen to fibrin to form a stabilized plaatelet plug?

A

Thrombin

19
Q

What two tests are commonly used to evaluate platelet function?

A

Platelet count as a part of a CBC

Bleeding time which will be prolonged if

20
Q

This type of QUALITATIVE platelet disorder is characterized by as a disorder in adhesion. It is the most common congenital bleeding disorder. It leads to a primary and secondary bleeding disorder. What is it?

A

Von Willebrands disease.

21
Q

What test can you use to test the activity of vWF?

A

Ristocetin cofactor activity test

22
Q

What drug can you use to treat type I vWD?

A

DDAVP because it enhances the release of vWF from endothelial stores

23
Q

What is Bernard-Soulier syndrome?

A

A rare autosomal recessive disorder where expression of GP1b on the platelet surface is reduced

Abnormal ristocetin test

24
Q

What is gray platelet syndrome?

A

Deficiency in dense granules or alpha-granules

25
Q

Afibrogenemia is a rare inherited defect that results in a decreased amount of what protein?

A

Fibinogen

26
Q

What rare autosomal recessive bleeding disorder is characterized by the absence of defective GPIIb-IIIa?

A

Glanzmann thrombasthenia

27
Q

What is the normal platelet range?

A

150,000-400,000

28
Q

At what platelet count could you expect patients to spontaneously hemorrhage?

A
29
Q

At what platelet count could you expect patients to spontaneously hemorrhage intracranially?

A

10-20,000

30
Q

What is the most common cause of thrombocytopenia due to increased destruction?

A

Immune thrombocytopenic purpura

31
Q

What are the two forms of ITP?

A

Acute and chronic

32
Q

What patient population do you usually see acute ITP?

A

Children and young adults after a viral infection

Onset is sudden and severe

33
Q

What patient population do you usually see chronic ITP?

A

In adult patients with other autoimmune disorders, lymphoma, or HIV. Or idiopathic

Most patients require treatment

34
Q

What are three treatments for patients with chronic ITP?

A
  1. Corticosteroids
  2. IVIG
  3. Splenectomy
35
Q

What is alloimmune thrombocytopenia?

A

Occurs when a patient develops antibodies to platelet antigens not present on the patient’s own platelets

36
Q

What is the mechanism of drug induced immune thrombocytopenia?

A

Drug binds to the platelet surface glycoprotein and creates a neooepitope

37
Q

Name some nonimmune-mediated causes of thrombocytopenia.

A

DIC
sepsis
thrombotic thrombocytopenic purpura (TTP)
hemolytic uremic syndrome (HUS)-more often in children presents like TTP but with a majority of renal failure. association with bacterial toxin

*All of these disorders are due to increased platelet consumption

38
Q

Thrombotic thrombocytopenic purpura (TTP) is characterized by fever, renal insufficiency, microangiopathic hemolytic anemia, mental status changes, and thrombocytopenia. They have characteristic large vWF multimers. This deficiency is caused by a decrease in what protein?

A

ADAMTS13 which normally digests the vWF into smaller multimers

39
Q

Is thrombotic thrombocytopenic purpua more commonly congenital or acquired?

A

Acquired due to the development of autoantibodies to ADAMTS13

40
Q

What is the treatment for thrombotic thrombocytopenic purpura?

A

Pheresis of vWF and replacement of missing ADAMTS13

41
Q

Name some basic bleeding tests used to evaluate excessive bleeding.

A 
Platelet count and blood smear
Bleeding time and PFA-100
APTT 
PT/INR
Thrombin clotting time
Fibrinogen level

Blood and Lymph Unit 3 (12 decks)

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