B3.066 Prework Thrombocytopenia

Question 1

what are platelets

Answer 1

small non-nucleated blood cells which are derived from bone marrow megakaryocytes and released into the bloodstream

Question 2

platelet alpha granule contents

Answer 2

procoagulant factor 5, fibrinogen, vWF, heparin inactivator PF4 and growth factors

Question 3

platelet dense granules contents

Answer 3

ADP, serotonin, calcium

Question 4

function of GP2b3a

Answer 4

binds fibrinogen and vWF

platelet aggregation

Question 5

defect in GP2b3a

Answer 5

Glanzman’s thrombasthenia

Question 6

PDGF function

Answer 6

vascular repair

stimulates fibroblasts and growth

Question 7

function of calcium in platelets

Answer 7

aids in platelet conformational change prior to aggregation

cofactor for phospholipid C

Question 8

GP1b function

Answer 8

anchors platelet to endothelium during adhesion

Question 9

defect in GP1b

Answer 9

Bernard Soulier syndrome

Question 10

major systems involved in hemostasis

Answer 10

vascular system
platelets
coagulation system
fibrinolytic system
serine protease inhibitors

Question 11

minor systems involved in hemostasis

Answer 11

kinin system

complement system

Question 12

function of platelets

Answer 12

formation of temporary plugs that stop bleeding when blood vessels are injured
promoting key reactions in the coagulation cascade

Question 13

normal platelet count

Answer 13

150,000-400,000

Question 14

platelet function tests

Answer 14

PFA-100
platelet aggregation test
bleeding test (older, less specific and sensitive)

Question 15

PFA test

Answer 15

new lab screening test of platelet function that measures both platelet adhesion and aggregation
coating in a tube can stimulate platelets to aggregate and close a hole
collagen+epi
collagen+ADP

Question 16

platelet aggregation test

Answer 16

measures ability of various agonists to platelets to induce in vitro activation and platelet to platelet activation
when an agonist is added, the platelets aggregate and absorb less light and so the transmission increases and this is detected by the photocell

Question 17

4 main causes of thrombocytopenia

Answer 17

decreased platelet production
-impaired marrow
decreased platelet survival
-immune or nonimmune mediated
sequestration
-normal spleen: 30-35%
-enlarged spleen: 80-90%
dilution
-massive transfusion

Question 18

major causes of decreased platelet production

Answer 18

drug induced
infections
nutritional deficiencies
bone marrow failure
bone marrow replacement
ineffective hematopoiesis

Question 19

major causes of decreased platelet survival

Answer 19

immunologic destruction
nonimmunologic destruction 
-DIC
-thrombotic microangiopathies
-giant hemangiomas
sequestration
dilution

Question 20

symptoms of thrombocytopenia

Answer 20

20,000-50,000 can aggravate posttraumatic bleeding
<20,000 may be associated with spontaneous bleeding
small vessel bleeding
-petechiae, ecchymoses
-gum and nose bleeding
-GI bleeding, hematuria, excessive menstrual flow
-subarachnoid hemorrhage and intracerebral hemorrhage

Question 21

acquired defects related to defective platelet functions

Answer 21

aspirin

uremia