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31 Cards in this Set
- Front
- Back
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The four phases of blood clotting |
1. Vascular Phase |
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What mediates vasoconstriction following an injury? |
Neurogenic factors, endothelin |
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Von Willebrand factor (vWF) |
Glycoprotein that mediates the adherence of platelets to one another and to sites of vascular damage |
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GpIb (Glycoprotein 1B) |
binds von Willebrand factor, allowing platelet adhesion and platelet plug formation at sites of vascular injury. |
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What do platelets release to attract more platelets and cause vasoconstriction? |
ADP and TXA2 |
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Dipyridamole MOA |
Inhibits phosphodiesterase, so cAMP accumulates and blocks the platelet response to ADP; it also blocks the synthesis of thromboxane synthetase |
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Aspirin MOA |
Irreversibly inhibits cyclo-oxygenase |
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Clopidrogel MOA |
Blocks ADP |
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Tests for platelet disorders |
1. Platelet count |
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Clinical signs of platelet deficiency |
(*Increased bleeding time) Petechiae, purpura, ecchymosis, |
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Clinical signs of clotting factor deficiency |
(*Normal bleeding time after injury) Re-bleeding, Menorrhagia, Hemoarthroses, GI bleeds |
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What activates the coagulation phase? |
Tissue factor; Further activation occurs on phospholipid surface of platelets |
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What do clotting factors II, VII, IX, and X have in common? |
They are dependent on vitamin K |
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The three interacting pathways of the coagulation cascade |
1. Extrinsic (Factor 7)
***note that this division is is an artifactual classification |
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Trigger for the coagulation cascade |
-Release of tissue factor by endothelial cells |
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The extrinsic system is triggered by what? |
Tissue thromboplastin |
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Fibrinolytic phase |
1. Tissue plasminogen activator (t-PA) : plasminogen to plasmin |
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Natural anti-coagulants |
• Anti-Thrombin III – inhibits thrombin, IXa,Xa, |
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Coagulation system tests |
Prothrombin time (extrinsic pathway) |
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Heparin MOA |
Activates antithrombin |
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Fibrinolytic system tests |
Fibrin degradation product (FDP assay): D-dimer • Thrombolytic therapy for CAD. • DIC (Disseminated intravascular coagulation)
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What changes in PT, PTT, BT, and platelet count would you see in someone with vitamin K deficiency (or on warfarin)? |
PT: increased (extrinsic pathway) PTT: normal BT: normal Platelet count: normal |
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What changes in PT, PTT, BT, and platelet count would you see in someone with DIC (septicemia/snake bite--patient presents with thrombosis and hemorrhage)? |
PT: increased PTT: increased BT: increased Platelet count: decreased
In DIC, all the coagulation factors are eaten up |
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What changes in PT, PTT, BT, and platelet count would you see in someone with von Willebrand disease? |
PT: normal PTT: increased (b/c factor VIII involved) BT: increased Platelet count: normal |
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What additional tests are helpful in diagnosing DIC? |
D-dimer (fibrinolytic activity) FDP (fibrin degradation products) |
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What changes in PT, PTT, BT, and platelet count would you see in someone with hemophilia? |
PT: normal PTT: increased BT: normal Platelet count: normal |
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What changes in PT, PTT, BT, and platelet count would you see in someone taking aspirin? |
PT: normal PTT: normal BT: increased Platelet count: normal |
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What additional test would you do to confirm that a patient had von Willebrand disease? |
Ristocetin cofactor assay |
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Is bleeding time due to platelets or clotting factors? |
Platelets |
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What changes in PT, PTT, BT, and platelet count would you see in someone with uremia? |
PT: increased PTT: normal BT: increased Platelet count: normal
excess nitrogenous wastes decrease platelet activity (BT) and interrupt coagulation factors (PT) |
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What does thrombin time (TT) tell you? |
thrombin time gives us a look at the common pathway; increased TT suggests a problem with fibrinogen |
