ch 27 alterations in hemostasis

Question 1

Thrombocytopenia is caused by what three basic mechanisms

Answer 1

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

**spurious thrombocytopenia

Question 2

How does spurious thrombocytopenia occur?

Answer 2

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

Question 3

Splenic platelet sequestration occurs as a result of what

Answer 3

splenomegally

Question 4

Which disorders result in splenomegally, thus potentially thrombocytopenia?

Answer 4

-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

Question 5

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

Answer 5

–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

Question 6

What are clinical signs of thrombocytopenia?

Answer 6

petechial or ecchymotic hemorrhages
epistaxis
melena
hyphema
hematuria

Question 7

when does spontaneous hemorrhage occur?

Answer 7

below 10,000 to 20,000/uL

Question 8

A physiologic increase in platelet count can occur when?

Answer 8

at a high altitude

Question 9

What are examples of drugs that impair platelet function?

Answer 9

-aspirin
-phenylbutazone
-sulfonamides
-estrogens
-phenothiazines

Question 10

What is physiologically the most important inhibitor of coagulation?

Answer 10

antithrombin III (ATIII)