EXAM #1: THROMBOCYTOPENIA Flashcards Preview

Hematology and Oncology > EXAM #1: THROMBOCYTOPENIA > Flashcards

Flashcards in EXAM #1: THROMBOCYTOPENIA Deck (32):
1

What is the definition of thrombocytopenia?

Platelet count less than 150,000/microliter

2

Describe the appearance of platelets on PBS.

- Round- oval
- Blue-gray
- 1/3 the size of a RBC
- Anuclear

3

Where are platelets produced? What are they released from?

- Produced in the bone marrow
- Megakaryocytes

4

What regulates platelet production? Where is this factor synthesized?

Thrombopoietin, which is synthesized in the liver

5

What receptor is activated after binding of Gp1b to vFW?

GpIIb/IIIa, which binds fibrin

6

What are the three underlying causes of thrombocytopenia?

1) Underproduction
2) Destruction
3) Sequestration

7

What are some of the infectious causes of platelet underproduction?

1) HIV
2) Parvovirus B19

8

What is the most common cause of underproduction of platelets from the bone marrow?

- Chemotheraputic agents
- Alcohol

9

If the MCV is greater than 115 or more, what should you think?

Megaloblastic anemia i.e. B12 or Folate

10

What is the mechanism of thrombocytopenia in pernicious anemia?

B12 is necessary to DNA synthesis, i.e. synthesis of platelet precursors

11

What will the megakaryocyte levels be in pernicious anemia?

Normal to increased numbers for megakaryocytes

12

What cancer is associated with pernicious anemia?

Gastric carcinoma

13

How is pernicious anemia managed?

B12 supplementation

14

What is pseudothrombocytopenia?

Platelet aggregation or clumping in vitro leads to a low count

15

What triggers pseudothrombocytopenia? How do you correct for it?

- EDTA
- Recheck with citrated or heparanized blood tube i.e. purple tube

16

What is ITP?

Idiopathic or Immune Thrombocytopenic Purpura

17

Describe the pathology of ITP.

- Accelerated destruction of platelets b/c antibody coated platelets are destroyed by macrophages in spleen
- GpIIb/IIIa
- Normal or increased megakaryocytes
- Diagnosis of exclusion*

18

What is the typical clinical presentation of ITP?

Often asymptomatic with SEVERE thrombocytopenia

****Some have purpura, petechiae...etc. but LIFE-THREATENING bleeding is RARE****

19

What is the treatment for ITP?

- Observation
- Steroids
- IVIG--coat receptors with something other than antiplatelet antibody
- Rituximab
- Thrombopoetin
- Splenectomy

20

What are the two classes of platelet destruction?

- Immune-mediated
- Nonimmune-mediated

21

List the causes of immune-mediated platelet destruction.

- ITP
- HIT
- Post transfusion purpura
- Medications
- Antiphospholipid antibody syndrome

22

List the causes of nonimmune-mediated platelet destruction.

- DIC
- TTP/HUS
- HELLP Syndrome
- Gestational Thrombocytopenia
- Mechanical Destruction
- Localized intravascular coagulopathy

23

What is HIT?

Heparin Induced Thrombocytopenia
- Immune mediated destruction of platelets
- Antibodies to heparin AND platelet-specific PF4 complex
- Activates platelets and leads to thrombosis

24

What form of Heparin has a lower risk of HIT associated?

LMWH

25

How is HIT managed?

1) STOP heparin
2) Use alternative anti-coagulant

26

Can you use Heparin again in a patient that has developed HIT?

Yes, if they have been Heparin free for 6 months

27

What does jaundice not involving the sclera indicate?

NOT hyperbilirubinemia

28

What causes sequestration of platelets?

Splenomegaly leads to splenic sequestration

- Portal HNT
- Hereditary spherocytosis
- CML
- Hairy cell leukemia
- MALT lymphoma

29

How do you evaluate thrombocytopenia?

1) HIP and PE
2) Lab eval
3) Bone marrow biopsy

30

When is bone marrow indicated?

1) Multiple cell lines involved
2) Greater than 60 with isolated thrombocytopenia
3) When empiric therapy is unsuccessful

31

What is the formula for platelet transfusion?

1 unit= increase in 5,000

Normal 6-pack is 30,000

32

When is platelet transfusion a BAD idea?

ITP
HIT