Flashcards in Coagulation Testing Deck (58):
What is hemostatsis the balance between?
-The bodies need to respond to injury by preventing hemorrhage by initiating thrombosis
-Maintaining effective circulation
What are the 3 components of hemostasis
1. Vessel wall
3. Coagulation system
What carries out primary hemostasis
What are the components of primary hemostasis
-Adhesion of collagen to the site of vascular injury
-Adhesion of other platelets
-Release of platelet contents to promote platelet aggregation
-Provision of a phospholipid surface to assemble proteins of the coagulation cascade
What are examples of platelet contents?
-Calcium clotting factors
Why is the phospholipid surface so important?
-Crucial for organizing and promoting interactions of clotting factors
What carries out secondary hemostasis?
The coagulation system
_______ circulate until they are activated
What is the coagulation cascade divided into?
Are these cascades separate, or work in conjunction with each other?
Work in conjunction with eachother
Why are the pathways useful?
-Understanding in vitro lab tests
-Identifying specific factor deficiencies
Disruption of the endothelium results in the exposure of...
Tissue factor (thromboplastin) in subendothelial tissue
Exposure of tissue factor results in the ______ pathway
How is the extrinsic pathway triggered?
Converting Factor 7 to 7a
The endothelial disruption also exposes ______ in the vascular wall
The exposure of collagen results in the activation of ______________ in the _______ pathway
-Contact phase proteins in the intrinsic pathway
Contact phase enzymes are also called...
T/F- Triggering of the extrinsic and intrinsic pathways occur simultaneously
What are the 2 activators of the coagulation cascade?
-Tissue Factor (extrinsic)
-Contact phase proteins (intrinsic)
What are 3 examples of contact phase proteins?
-High molecular weight kininogen
-Factor 12 (hagpan factor)
What are the 4 Vitamin K dependent factors?
2, 7, 9, 10
Where are vitamin K dependent factors formed?
What do factors 2, 7, 9, 10 require as a cofactor for optimal activity of the clotting cascade?
What synthesizes Vitamin K
Normal flora of the GI tract
-or obtained in diet from leafy green veggies
What are 3 causes of Vitamin K deficiency
-Broad spectrum antibiotics (disrupt normal flora)
-Coumadin (inhibits vitamin K factors
What are the cofactors?
7a and 5a
What happens if you do not have the correct cofactors
Factors 9 and 10 have reduced activity and clotting is impaired
The conversion of ______ to _____ produces a soft clot
Fibrinogen to fibrin
What factor stabilizes the soft clot
What happens if you have a deficiency in inhibitors of coagulation?
You get a hypercoagulable state
Hypercoagulatible states increase the incidence of _______
What are examples of thrombotic events
____________ in the presence of fibrin and components of contact phase convert circulating plasminogen into plasmin
Tissue plasminogen activator (tPA)
What is the active enzyme of plasminogen?
This is a naturally occurring anticoagulant in the presence of tissue heparin or exogenous heparin
What is the function of antithrombin 3
-Heparin complex that inhibits the enzyme activity of factor 2a (thrombin), 4a, and 5a
When this protein is activates, it is an enzyme that cleaves and destroys the factors 13a and 10a
This is a cofactor for protein C
Will protein C be effected by vitamin K deficiency?
Yes- because protein C is a vitamin K dependent enzyme and will be effected by vitamin K defieciency or Coumadin therapy
This is a coag. test that tests the...
Protrombin time (PT/INR)
How do you test PT?
-Take a sample of plasma
-Add tissue factor and calcium
-Measure the time it takes fibrin to form a clot
Does Coumadin effect PT?
(extrinsic, Coumadin is given OUTpateint)
What is tissue factor derieved from that it can have great variability in the results of the PT
To reduce variability, PT is converted to...
International normalized ratio (INR)
What is a normal INR for a healthy patient?
The higher the INR, the thinner/thicker the blood
What is an example when an elevated PT/INR (normal PTT) are seen?
-Vitamin K deficiency
What does activated partial thromboplastin measure?
Intrinsic clotting pathway
How do you test PTT
-Take plasma sample
-Add calcium and contact phase activator
-Results are recorded by the amount of time it takes fibrin to clot
When is elevated PTT seen?
When are fibrinogen levels used?
-IN hypercoagulatible state workups
How do you test fibrinogen levels?
-Adding bovine thrombin to a sample of plasma
In most cases, determining the status of Protein C, protein S, and antithrombin levels will be low yield and not cost effective
Factor 5 Lieden results from a single amino acid mutation of factor 5. What does this cause?
-found more commonly in PE and DVT patients
What are additional tests for hypercoagulatibity work up?
-Lupus anticoagulant levels
What increases the risk for hypercoagulable states?