Pathoma: 2a hemostatsis and related disorders Flashcards
What is the goal of 2a hemostasis?
to stabilize the platelet plug
How does 2a hemostasis achieve its end goal?
via the coagulation cascade
What is the receptor for platelet aggregation?
GPIIb/IIIa
What molecule links the platelets via GPIIb/IIIa?
fibrin
What is the end product of the coagulation cascade?
thrombin
What does thrombin do?
it converts fibrinogen to fibrin
What gets crosslinked to generate a stable platelet plug?
fibrin
What 3 things does activation require?
- exposure to an activating surface
- phospholipid surface
- calcium
Where does the calcium come from?
dense platelet granules
In general, a disorder of 2a hemostasis is due to _____.
factor abnormalities
______ is the major clinical feature of 2a hemostasis.
Deep bleeding (into muscles and joints) and rebleeding after surgery
In 1a hemostasis, the primary problem is ______.
superficial bleeding (into mucosa and
What is the PT test?
a measure of extrinsic and common factors
What is the PTT test?
a measure of intrinsic and common factors
What is the order of the intrinsic pathway factors, ending at 10?
12, 11, 9, 8, 10
What is the order of the intrinsic pathway factors, ending at 10?
7, 10
What is the order of the common pathway, starting at 10?
10, 5, 2, 1
What activates factor 12 (the intrinsic pathway)?
subendothelial collagen (SEC) * PTT and SEC are both 3 letters
What activates factor 7 (the extrinsic pathway)?
tissue thromboplastin (TT) * TT and PT are both 2 letters
Which test is better for measuring heparin?
PTT
* PTT and HEP are both 3 letters
Which test is better for measuring warfarin/Coumadin?
PT
What is hemophilia A?
an X-linked defect of factor VIII (8)
* hemophilia AAAAA-eight
How do hemophilia A pts present?
deep tissue, joint, and post-surg bleeding
The clinical severity of hemophilia A depends on _____.
the degree of deficiency
Hemophilia A lab results?
increased PTT normal PT decreased FVIII normal platelets normal bleeding time
What is the treatment for Hemophilia A?
give recombinant factor VIII
What is Hemophilia B?
a genetic factor IX (9) deficiency
What is another name for Hemophilia B?
Christmas disease
What is a coagulation factor inhibitor?
an autoantibody against a coagulation factor, impairing its function
Which factor is commonly targeted by coagulation factor inhibitors?
factor VIII (8)
Clinically, how can you tell the difference btw Hemophilia A and a coagulation factor inhibitor against factor VIII?
A mixing study: the increased PTT can be corrected in Hemophilia A by mixing pt’s plasma with a normal plasma, but this can’t happen if an inhibitor is present
What is Von Willebrand disease?
the most common inherited coagulation disorder- deficiency of vWF
What is the most common subtype of vW disease?
auto. dominant; decreased vWF levels
How does a vW Disease pt present?
mild mucosal and skin bleeding
What does low vWF cause?
impaired platelet adhesion
What are the lab findings in vW Disease?
increased bleeding time
increased PTT
normal PT
abnormal ristocetin test
Why is the PTT increased in vW Disease?
vWF stabilizes factor VIII (8)
What is the ristocetin test?
ristocetin given to platelets makes them aggregate- if there’s no vWF, they won’t clump
What is the tx for vW Disease ?
desmopressin
How does desmopressin work?
it increases vWF release from the Weibel-Palade bodies in endothelial cells
* W for vWF, P for P-selectin
What is Vitamin K deficiency?
disrupted coagulation
Why is Vitamin K so important for coagulation?
it’s necessary for gamma-carboxylation of factors 2, 7, 9, 10, C, and S
Vitamin K is activated by ____ in the ____.
epoxide reductase; liver
_____ blocks epoxide reductase.
Coumadin
When can vitamin K deficiency present?
- newborns
- long-term Abx
- malabsorption (esp fat)
- liver failure
Why does long term Abx therapy cause Vitamin K deficiencies?
vit K is synthesized by normal gut flora
How is vitamin K deficiency prevented in newborns?
they’re all given a prophylactic vitamin K shot at birth
What test would check the effect of liver failure on coagulation?
PT
What happens when large volume transfusions are given?
coagulation factors are diluted, leading to deficiencies
