ch 27 alterations in hemostasis Flashcards
Thrombocytopenia is caused by what three basic mechanisms
1.platelet sequestration
2. decreased platelet production
3. decreased platelet life span d/t consumption or destruction
**spurious thrombocytopenia
How does spurious thrombocytopenia occur?
when blood is collected into EDTA anticoagulant
**collection of second sample with sodium citrate for accurate plt count
Splenic platelet sequestration occurs as a result of what
splenomegally
Which disorders result in splenomegally, thus potentially thrombocytopenia?
-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
What are examples of disorders that result in decreased platelet production?
–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
What are clinical signs of thrombocytopenia?
petechial or ecchymotic hemorrhages
epistaxis
melena
hyphema
hematuria
when does spontaneous hemorrhage occur?
below 10,000 to 20,000/uL
A physiologic increase in platelet count can occur when?
at a high altitude
What are examples of drugs that impair platelet function?
-aspirin
-phenylbutazone
-sulfonamides
-estrogens
-phenothiazines
What is physiologically the most important inhibitor of coagulation?
antithrombin III (ATIII)