General, Week 3 Cardio Flashcards
what does thrombin do in the clotting cascade?
conversion of fibrinogen to fibrin
what is the main result of primary hemostasis?
formation of a platelet plug
what is the main result of secondary hemostasis?
formation of an insoluble fibrin clot (mortar for the platelet bricks)
what does the D-dimer tell you?
what makes/releases the D-dimer
if the patient is clotting or not
- plasmin (which breaks up fibrin cross links) releases the D-dimer
what does factor 13 do in clotting?
it cross links the fibrin
what laboratory clotting test tests the instristic pathway?
what about the extrinsic pathway?
PT - extrinsic (TF and F7)
APTT - intrinsic (F12, F11, F9, F8)
what does antithrombin do in the body?
inhibits thrombin and certain coagulation factors
what does t-PA do?
what releases it?
activates plasminogen –> plasminogen + tPA activate plasmin, which breaks the fibrin clot and releases D-dimers
endothelial cells release tPA
what are the three ways that the body physiologically limits clot size?
- prothrombin
- Protein C and Protein S
- t-PA, plasminogen –> plasmin
the binding of what with thrombin activated protein c?
thrombomodulin (on endothelial cells)
what is the test of control (lab clotting times) for unfractionated heparin?
APTT (intrinsic pathway)
what are the factors that predispose thrombosis? Virchow’s triad
- endothelial injury
- stasis
- hyper coagulability (inherited or acquired)
with unfractionated heparin, what is the danger of giving it? (why do you need testing)
it binds to other proteins in plasma - don’t really know what dose you need
variable responses (can bind non -plasma protein, don’t really know how much you need)
with LMWH (low molecular weight heparin), why don’t you need to use the test of control?
much more predictable
doesn’t bind a bunch of non-anticoagulant proteins (because it is shorter), know how much you should give, less variable
what is the mechanism of UFH (unfractionated heparin)
it binds antithrombin, changing its shape and making it better able to bind F10a
ALSO, the UFH is long enough to wrap around and also bind thrombin
what is the mechanism of LMWH?
only long enough to bind to antithrombin
produces conformational change
this allows antithrombin to better bind 10a
what is fondaparinux?
what is its mechanism?
it is a synthetic analog of just the heparin binding interaction with antithrombin
it binds antithrombin –> conformational change –> better binds F10a
how do you give heparin? (either of the 3 forms)
IV or subQ
what can unfractionated heparin be reversed with?
what about LMWH?
protamine sulfate
not sufficient for LMWH or fondaparinux
what are the two major adverse effects of heparin?
- hemorrhage
- heparin induced thrombocytopenia (HIT)
HIT greater in UFH, less in other two
what does heparin induced thrombocytopenia - HIT -cause (2)?
it causes a decrease in platelet count (they are activated and consumed and going into a thrombus)
THROMBUS FORMATION because of IgG against heparin and PF4
how can you diagnose HIT?
decrease in platelet count ( > 50%)
PLATELET COUNT (and clinical circumstance, did they just undergo a major surgery?)
how do you manage HIT?
- cessation of heparin
2. direct thrombin inhibitor - argatroban
what is argatroban?
what is it used for?
it is a direct thrombin inhibitor
used for heparin induced thrombocytopenia
