Pathoma - 4 (Hemostasis)

evolv3's version from 2015-06-20 22:10

Section 1

Question Answer
Weak platelet plug?primary hemostasis
coagulation cascade that stabilizes the weak platelet plug?secondary hemostasis
what causes the transient vasoconstriction in primary hemostasis?endothelin release from endothelial cells and reflex neural stimulation
what 2 things produce vWF?Weibel-Palade bodies of endothelial cells and alpha-granules of platelets
what molecule released from the platelet induces the exposure of gpIIB/IIIA?ADP
what does TXA2 do?promotes platelet aggregation
what are the 2 stages of hemostasis?weak platelet plug and coagulation cascade
Whats normal bleeding time?2-7 minutes

Section 2

Question Answer
what causes immune thrombocytopenic purpura?autoimmune IgG against gpIIb/IIIa on platelets
whats the most common cause of thrombocytopenia?ITP
whats the MOA of ITP?antibody-bound platelets are eaten by splenic macrophages --> thrombocytopenia
what autoimmune disease is associated with secondary ITP?SLE
whats the tx for ITP?IVIG (splenic macrophages will eat this Ig instead of IgG-platelets) and splenectomy (since autoantibodies are produced by plasma cells in the spleen)
which 3 diseases show microangiopathic hemolytic anemia?thrombotic thrombocytopenia purpura and HUS, DIC
what causes TTP?decrease ADAMTS13 --> leading to large multimers of vWF
what causes HUS?E. coli verotoxin (E. coli 0157: H7) which damages endothelial cells resulting in platelet microthrombi
why is aspirin an antiplatelet?aspirin irreversibly inhibits COX --> decreased TXA2 impairs platelet aggregation
which enzyme converts fibrinogen to fibrin in platelet plug?thrombin
what activates factor VII?tissue thromboplastin (extrinsic pathway)
what activates factor XII (intrinsic pathway)?subendothelial collagen
deep tissue bleeding into muscles and joints, and post-surgical bleeding is a sign of?secondary hemostasis

Section 3

Question Answer
what does prothrombin time (PT) measure?factor VII and common pathways (factors II, V, X)
what does Partial Thromboplastin Time (PTT) measure?factors 12, 11, 9, 8 and common pathway
pt presents with increased bleeding time and increased PTT?vWF deficiency (increased bleeding time due to bad platelet adhesion and increased PTT since vWF stabilizes FVIII)
abnormal ristocetin test?vWF deficiency or bernard soulier
what is the ristocetin test used for?ristocetin induces platelet adhesion by causing vWF to bind to gpIb (lack of vWF --> impaired adhesion --> abnormal test & abnormal for bernard soulier as well
whats the tx for vWF deficiency?desmopressin (ADH analog) = increases vWF release from Weibel-Palade bodies
whats the MOA of warfarin?inhibits epoxide reductase --> no activation of vit K --> no gamma carboxylation of factors 2, 7, 9, 10, protein C and S
what causes heparin-induced thrombocytopenia?autoantibody against heparin-(platelet factor 4) complex
what is DIC?abnormal activation of coagulation cascade due to another disease process
what triggers DIC in pregnant women?tissue thromboplastin in amniotic fluid
what triggers DIC in adenocarcinoma?mucin triggers coagulation
whats the best screening test for DIC?D-dimer = produced from splitting of the cross-linked FIBRIN
What converts plasminogen to plasmin?tPA
whats the role of plasmin in fibrinolysis?plasmin cleaves fibrin and fibrinogen, destroys coagulation factors and BLOCKS PLATELET AGGREGATION
what activates plasmin (for fibrinolysis) in radical prostectomy?UROKINASE activates plasmin
whats the tx for disorders of fibrinolysis?aminocaproic acid = blocks activation of plasminogen so plasmin CANT be formed
whats the lab differences in DIC vs. disorder of fibrinolysis?DIC = decreased platelets, increased D-dimer.
DOF = normal platelets and no D-dimer
what distinguishes a thrombus from post-mortem blot?lines of Zahn and will be attached to blood vessel wall
which 2 factors does Protein C inactivate?factors V and VIII
homocysteine + methyl methionine

Section 4

Question Answer
What are 3 causes of endothelial cell damage?atherosclerosis, vasculitis, high levels of homocysteine
Whats a cause of increased levels of homocysteine?lack of vit B12 or folate = leads to decreased conversion of homocysteine to methionine resulting in build up of homocysteine
How does protein C and S deficiency cause a hypercoagulable state?normally protein C and protein S inactivate clotting factors V and VIII --> if theres a deficiency in protein S and C, then you will have increased activation of clotting factors V and VIII
How does prothrombin 20210 cause a hypercoagulable state?point mutation in prothrombin --> increased prothrombin --> increased thrombin --> increased conversion of fibrinogen to fibrin
how does OCP induce a hypercoagulable state?estrogen increases production of coagulation factors