Normal Hemostasis Flashcards
T or F. Thrombin cleaves two fibrinopeptides (A and B) from fibrinogen to make fibrin
T, going from an an soluble fibrinogen to a insoluble fibrin
What activates Factor XIII?
thrombin
What does FXIII do?
converts the hydrogen bond between fibrin and platelets to a covalent bond
What is needed for conversion of prothrombin to thrombin?
-calcium
-Xa/Va
and a phospholipid surface
How is FVIII activated once released from alpha granules on platelets?
TF (it then binds to IXa)
What is lacking in serum?
fibrinogen
How is a PT done?
add TF + phospholipid (aka thromboplastin) complex (used to promote clotting for a PT time along with Ca2+ input) to PLASMA not serum (extrinsic)
How is aPTT done?
use citrated plasma and add phospholipid only (without TF) and add Ca2+ and a negative charge and measure time (intrinsic)
What clotting factor deficiency could you have if you had a normal PT and a long PTT?
VIII, IX, XI, or XII
What clotting factor deficiency could you have if you had a long PT and a normal PTT?
VII
What clotting factor deficiency could you have if you had a long PT and a long PTT?
X, II
What clotting factor deficiency could you have if you had a normal PT and a normal PTT?
XIII (very rare)
How could you screen for XIII deficiency cheaply?
you would have a hydrogen bonded clot that didn’t get covalently bonded so you can put the clot in something unfavorable to hydrogen (5M-urea) and see if it dissociates
What does VIII need to function (bind)?
vMF (it the carrier of factor VIII)
T or F. vMF is normal in Hemophilia A patients
T. patients just cant make VIII
What is D-dimer?
a combo that is never seen on fibrin and indicates fibrinolysis of cross-linked fibrin (good diagnostic tool for suggesting a clot has formed-PE or MI- not perfect)
(fibrinogen digestion products can be indicative of fibrinogen breakdown- not fibrin)
What is the MOI of Hemophilia?
X-linked recessive (thus women are the only carriers)
What does thrombomodulin do?
located on endothelial cells and changes thrombin’s target to activate protein C (vitamin K dependent)
What is Factor V Leiden?
mutation in V that makes it resistant to inactivation via protein C
What does antithrombin III do?
made in liver binds to heparin and is a protein that neutralizes the serine protease active site (on II, X, and IX- not VII)
What does heparin do?
essentially catalyzes antithrombins ability to neutralize the serene proteases II, IX, and X
T or F. Heparin sulfate in the body are naturally occurring antithrombin catalysts.
T.
T or F. Plasmin is not found floating in the body.
T. because antiplasmin a2 will neutralize it quickly
The differential diagnosis for thrombocytopenia should always start with what?
lab artifact- pediatric or adult
What is the target population for TTP?
women in 20-30s
T or F. TTP is an autoimmune disease
T. antibody to ADAMTS13 which trims vMF
What is the cause of death in TTP?
ischemic organ failure
What is the treatment for TTP?
plasma exchange therapy
What is the diagnosis for ITP?
diagnosis of exclusion (garbage can category)
rule out problems with sequestration, bone marrow function and then call it this
What is ITP?
immune (idiopathic) thrombocytopenia purpura
In a pediatric setting, ITP can be a good cause if a child comes in with a lot of bruises (think abuse too) and will resolve mostly.
In a pediatric setting, ITP can be a good cause if a child comes in with a lot of bruises (think abuse too) and will resolve mostly.
T or F. In ITP antibodies that bind platelets, they are likely to bind megakaryocytic too
Thus, decreased production is also a problem with ITP
treat with steroids here
