B3.066 Prework Thrombocytopenia Flashcards
what are platelets
small non-nucleated blood cells which are derived from bone marrow megakaryocytes and released into the bloodstream
platelet alpha granule contents
procoagulant factor 5, fibrinogen, vWF, heparin inactivator PF4 and growth factors
platelet dense granules contents
ADP, serotonin, calcium
function of GP2b3a
binds fibrinogen and vWF
platelet aggregation
defect in GP2b3a
Glanzman’s thrombasthenia
PDGF function
vascular repair
stimulates fibroblasts and growth
function of calcium in platelets
aids in platelet conformational change prior to aggregation
cofactor for phospholipid C
GP1b function
anchors platelet to endothelium during adhesion
defect in GP1b
Bernard Soulier syndrome
major systems involved in hemostasis
vascular system platelets coagulation system fibrinolytic system serine protease inhibitors
minor systems involved in hemostasis
kinin system
complement system
function of platelets
formation of temporary plugs that stop bleeding when blood vessels are injured
promoting key reactions in the coagulation cascade
normal platelet count
150,000-400,000
platelet function tests
PFA-100
platelet aggregation test
bleeding test (older, less specific and sensitive)
PFA test
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
platelet aggregation test
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
4 main causes of thrombocytopenia
decreased platelet production -impaired marrow decreased platelet survival -immune or nonimmune mediated sequestration -normal spleen: 30-35% -enlarged spleen: 80-90% dilution -massive transfusion
major causes of decreased platelet production
drug induced infections nutritional deficiencies bone marrow failure bone marrow replacement ineffective hematopoiesis
major causes of decreased platelet survival
immunologic destruction nonimmunologic destruction -DIC -thrombotic microangiopathies -giant hemangiomas sequestration dilution
symptoms of thrombocytopenia
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
acquired defects related to defective platelet functions
aspirin
uremia
