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15 Cards in this Set
- Front
- Back
coagulation factors for each of the pathways
Intrinsic: Extrinsic: Common: |
Intrinsic: 12,11, 9,8,10,5,2 and fibrinogen
Extrinsic: 10,7, 5,2and fibrinogen(1) Common: 10, 5, 2 and fibrinogen(1) |
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Factors 5a and 8a act as cofactors to mediate the activation of other players in the coagulation cascade
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factor 8a helps 9a activate 10; factor 5a helps 10a activate 2 (trombin)
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distinguish FDP and D-dimer
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FDPs may be generated by the degradation of either fibrin or fibrinogen; D-dimers are products of fibrin alone and more specifically indicate that clotting has taken place
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define the prothrombin time test; what coagulation factors are supplied as reagents
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PT test: reagent tissue thromboplastin (factor3) is mixed with the patient plasma; (factor 3 activates factor 7 in the extrinsic pathway in normal clotting); then calcium is added as reagent calcium chloride and the time to clot formation is measured
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True or False. The activated partial thromboplastin time (PTT) asseses physiologic hemostasis by evaluating the contact factors in the intrinsic coagulation system.
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False; the contact factors in the intrinsic pathway are evaluated BUT the PTT really doesn't assess physiologic homostasis
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difference between platelet and coagulation defect bleeding
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Platelet disorders: immediate bleeding, difficulty making the initial platelet plug
Coagulation: delayed bleeding after the breakdown of the initial platelet plug; they cannot generate the complete stable clot |
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explain why a patient with low factor 8 level and no inhibitor, the PTT corrects to reference range; if only half of the plasma in a mixing study contain adequate factor 8, shouldn't the PTT be twice normal?
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no, only 50% levels of any coagulation factor will result in clotting times that fall within reference range and will ensure adequate hemostasis for routine activities
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if a normal man has 80% clotting factor activity; how many units/ml of factor does he have?
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100% activity is equivalent to 1.0 unit/ml so 80% activity is 0.8 units/ml
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dosing formula for recombinant factor 8 for hemophilia A is :
dose (IU)= body weight(kg) x 0.5IU/kg x percent increas required Problem: patient with <1% activity , requires 50% activity , weighs 42kg, what is his dose? |
he'll need 1050IU; 42kg x 0.5IU/kg x (50-0%)= 1050IU
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45 yow marked prolong PTT on routine screening prior to elective surgery; she has 3 children and tooth extractions without excess bleeding; factor analysis shows one factor decreased; DX?
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factor 12 deficiency
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22yom mildlt prolonged PT and PTT on routine screen; increased bleeding with wisdom tooth extraction; fibrinogen antigen assay is within reference range; thrombin time prolonged;DX?
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dysfibrinogenemia; qualitative defect of fibrinogen; these patients have mild bleeding
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acquired factor deficiency in 8.7%percent patients with amyloidosis?
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factor 10
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couple with four children;
Andrew moderate hemophilia A with usual factor levels 4-5% In the ratio of factor 8 to vWF (normally 1:1) Three daughters would like to know if they are carriers? Anne: 0.45 Betty: 0.52 Cecilia: 1.09 |
test that will help is the ratio of factor 8 to vWF; normally it is 1:1; (vWF is a carrier for factor 8, they circulate in pairs); in carriers of hemophilia A who have factor levels of about 50%; this ratio is roughly 0.5:1.0; thus Anne and Betty appear to be carriers, Cecilia is not
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which routine screening and confirmatory tests are normal and which are abnormal in factor 13 deficiency?
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the PT and PTT are normal because the test ends with the formation of the fibrin monomer; crosslinking need not occur; in normal persons fibrin clots(crosslinked polymers)are stable in a solution of 5M urea; in factor 13 deficiency the clot will dissolve in 5M urea
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severe hemophilia A patient is known to have developed an inhibitor to factor 8; inhibitor was measured at 2 Bethesda units;he is given a dose of recombinant factor 8 that would raise his level to 100% if he had no inhibitor; expected factor 8 level?
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if severe hemophilia consider the starting factor level to be 0-1%;after the dose is given factor 8 will be near 25%; each Bethesda unit reduces the amount of factor 8 activity by one half;
here he went from 100 to 50, then 50 t 25 with 2 Bethesda units |