Test 2 Flashcards
hemostasis definition
the process of coagulation and lysis of clots in the body
four processes of hemostasis
- narrowing of blood vessels
- platelet activity
- activation of coagulation factors via intrinsic and extrinsic pathways
- fibrinolysis
excessive hemorrhage caused by
- delays in clot formation
- premature clot lysis
excessive thrombosis caused by
- inappropriate clot activation
- localization of the blood coagulation process
hyperreactivity of platelets leads to
arterial thrombosis
accelerated activity of the clotting system leads to
venous thrombosis
impaired coagulation caused by
- thrombocytopenia
- acquired coagulation disorders
- inherited factor deficiencies
activation of platelets steps
- adhesion
- aggregation
- fibrin formation
- clot retraction
platelet count panic values
<20
>1000
causes of thrombocytopenia
- decreased platelet production
- increased platelet destruction or consumption
- increased splenic sequestration
heparin induced thrombocytopenia (HIT)
- life threatening complication of exposure to heparin
- causes platelet activation that causes platelet consumption
- thrombosis risk is higher than bleeding risk
EDTA sensitivity (pseudothrombocytopenia)
- erroneous low platelet counts due to micro clumping of platelets in spite of anticoagulant in tube
- low platelet count without history of thrombocytopenia or bleeding episode*
- redraw specimen in tube with different anticoagulant
causes of thrombocytosis (high platelets)
- essential thrombocythemia (bone marrow over produces)
- reactive thrombocytosis
bleeding time
- measures the primary stage of hemostasis
- interaction of the platelet with the blood vessel wall and formation of hemostatic plug
platelet function analysis
-measures the time to form a platelet/RBC thrombus
platelet aggregation study
- gold standard for testing platelet response*
- measures if platelets aggregate, adhere, or release their granules
von Willebrands Type 1
- most common
- missing some VWF
- mild symptoms
von Willebrands Type 2
- defective VWF
- mild symptoms
von willebrands type 3
- limited or no VWF
- severe symptoms
von willebrand factor role
- VWF helps adhere platelets to exposed collagen in vessel walls
- VWF protects factor 8 from degradation by proteins C and S
von willebrands labs
- platelets = normal
- PTT = normal or increased
- VWF antigen = decreased
- factor 8 antigen = decreased
idiopathic thrombocytopenia purpura (ITP)
- unknown cause but usually follows viral illness in children
- platelets become bound to antibodies
ITP labs
- platelets = decreased
- bleeding time = increased
- PT/PTT = normal
ITP treatment
- splenectomy
- platelet transfusion for super low counts