ch 27 alterations in hemostasis Flashcards

1
Q

Thrombocytopenia is caused by what three basic mechanisms

A

1.platelet sequestration
2. decreased platelet production
3. decreased platelet life span d/t consumption or destruction

**spurious thrombocytopenia

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2
Q

How does spurious thrombocytopenia occur?

A

when blood is collected into EDTA anticoagulant
**collection of second sample with sodium citrate for accurate plt count

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3
Q

Splenic platelet sequestration occurs as a result of what

A

splenomegally

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4
Q

Which disorders result in splenomegally, thus potentially thrombocytopenia?

A

-infiltrative disorders: lymphoma, leukemia and multiple myeloma
-infectious & other inflammatory disorders: IMHA, lymphoid hyperplasia, splenic extramedullary hematopoiesis
-venous outflow occlusion: torsion, intestinal displacements, or congestive heart failure

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5
Q

What are examples of disorders that result in decreased platelet production?

A

–various bone marrow disorders: myelophthisis (replacement of bone marrow), infiltration of neoplastic cells, familial myelofiborsis (pygmy goats), toxic damage (braken fern tox, NSAID tox)
–immune mediated destruction of megakaryocytes

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6
Q

What are clinical signs of thrombocytopenia?

A

petechial or ecchymotic hemorrhages
epistaxis
melena
hyphema
hematuria

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7
Q

when does spontaneous hemorrhage occur?

A

below 10,000 to 20,000/uL

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8
Q

A physiologic increase in platelet count can occur when?

A

at a high altitude

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9
Q

What are examples of drugs that impair platelet function?

A

-aspirin
-phenylbutazone
-sulfonamides
-estrogens
-phenothiazines

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10
Q

What is physiologically the most important inhibitor of coagulation?

A

antithrombin III (ATIII)

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