Flashcards in Primary Hemostasis Deck (49)
What are the hallmarks of primary hemostasis?
formation of weak platelet plug
What is the goal of secondary hemostasis?
stabilization of platelet plug (mediated by coagulation cascade)
What is step one of damaged vessels?
transient vasoconstriction (knee jerk reaction to pull away)
What mediates step 1 (vasoconstriction)?
1) neural reflex
2) endothelial cells themselves secrete endothelin
What is von willebrand's factor?
a factor that will come line the break down
What allows for VWF to bind?
What is the function of VWF?
to serve as a linker to bind to platelets
Where does VWF come from?
2) endothelial cells (most important)
What holds VWF in the endothelial cell?
Wiebold pilate body
(WP - P reminds that most important is P selectin and W reminds of VWF)
What is step 3?
shape change in platelets that allows for dumping of mediators (ADP and thromboxane A2 TXA2)
TXA2 is a derivative of _________________
What is essential for platelet aggregation?
GP2b3a (glycoprotein 2b3a)
What is essential for the expression of GP2b3a?
What is the role of TXA2?
to further recruit platelets to aggregate
What is the important linker molecule between Gp2b3a and platelets?
platelet aggregation occurs via ________ using ___________ as a linker
binding of VWF to exposed collagen (and then platelets bind to VWF)
What receptor do platelets use to bind to VWF?
What promotes exposure of GpIIb/IIIa?
What are the classical signs and symptoms of primary hemostasis disorders?
mucosal or skin bleeding
What are examples of mucosal bleeding?
epistaxis (nose bleeding)
hemoptysis (coughing up blood)
What is the feared complication of a low platelet count?
What are examples of skin bleeding?
Petechiae are a sign of ______________
thrombocytopenia (few platelets not a qualitative problem)
What is a normal platelet count?
What produces platelets?
megakaryocytes in the bone marrow
What is ITP?
autoimmune disorder where you produce IgG against platelet antigens (like GPIIb/IIIa)
What is the most common cause of thrombocytopenia?
What produces those autoantibodies in ITP?
plasma cells in the spleen
macrophages in the spleen also consume the platelets that are bound to the antibody
What do lab results look like in ITP?
1) LOW platelets
2) normal PT/PTT
3) HIGH megakaryocytes
Why treat ITP with IVIG?
spleen will start eating IVIG instead of platelets with autoantibody (SHORT LIVED effect)
defend platelets for a short period of time
What is the most permanent solution to ITP?
What is microangiopathic hemolytic anemia?
get abnormal aggregation of platelets forming microthrombus which shears the RBCs that pass by -- called shistocyte (hemolysis)
What are complications of microangiopathic hemolytic anemia?
low platelet count (used up in forming microthrombus)
What are the 2 classic disorders that lead to microangiopathic hemolytic anemia?
1) TTP (thrombotic thrombocytopenic purpura)
2) HUS (hemolytic uremic syndrome)
Why do platelet thrombii occur in TTP?
decrease in ADAMTS13 enzyme (responsible for cleaving VWF multimers)
VWF multimers lead to abnormal platelet adhesion - results in platelets forming microthrombi
Why would you ever have a decrease in ADAMTS13?
autoantibody to destroy it (or genetic)
What bug causes HUS?
Ecoli O157 H7
Wheredo platelet microthrombi occur in HUS?
kidney and brain
Who gets Ecoli O157 H7?
children who eat undercooked beef (bug produces verotoxin)
What are some of the clinical findings in TTP and HUS?
1) skin and mucosal bleeding (platelets are consumed in microthrombi)
2) microangiopathic hemolytic anemia
4) renal insufficiency
5) CNS abnormalities
In TTP, the predominant problem is ________________ while in HUS, the predominant problem is _________________
CNS abnormalities (TTP)
True or False: PT/PTT are NORMAL in microangiopathic hemolytic anemia
TRUE (haven't activated coagulation cascade)
What is a big example of a qualitative platelet disorder?
Bernard Soulier syndrome (genetic GP1b deficiency)
What is the pathology of Bernard Soulier?
GP1b is gone so platelet adhesion is impaired (platelets cannot bind VWF)
What does blood smear show for bernard soulier?
1) mild thrombocytopenia (platelets have shorter life span)
2) enlarged platelets (immature)
Bernard Soulier get Big Suckers
What is Glanzmann thrombasthenia?
genetic GIIb/IIIa deficiency
platelets can still bind Gp1b to VWF and release ADP/TXA2 so GPIIb/IIIa will be expressed to recruit more platelets ---- dont have GPIIb/IIIa, this part of the cascade cannot happen
Why is aspirin a bleeding concern?
COX is irreversibly inactivated so you have decreased TXA2 -- less signal to aggregate
platelets cannot aggregate