Coagulation Flashcards
What are the four steps of hemostasis?
- Vascular spasm
- Platelet plug formation (primary homeostasis)
- Coagulation and fibrin formation (secondary homeostasis)
- Fibrinolysis
Where are platelets produced and by what?
bone marrow by megakaryocytes
List the three steps required to produce a platelet plug:
- adhesion
- activation
- aggregation
During what step does von Willebrand factor bind to the platelet?
step 1 - adhesion
During what step does von Willebrand factor bind to the platelet?
step 1 - adhesion
How does the injured blood vessel initially active the platelet plug?
Endothelial injury exposes collagen -> exposed collagen at site of vascular injury activates platelets.
Intrinsic pathway saying:
If you can’t buy the intrinsic pathway for $12, you might be able to for $11.98
Extrinsic pathway saying:
You can buy the extrinsic pathway for 37 cents
Final common pathway saying:
The final common pathway can be purchased at the five (5) and dime (10) for 1 or 2 dollars on the 13th of the month
What converts fibrinogen to fibrinogen monomer?
Thrombin
What is a normal aPTT value?
25-32 seconds
What is a normal PT value?
12-14 seconds
What is a normal INR value? What is therapeutic on warfarin?
~ 1
2-3 times normal
What is a normal ACT?
90-120 seconds
What must the ACT be before initiating CPB?
> 400 seconds
What is a normal platelet count?
150,000 - 300,000 mm3
What is normal bleeding time?
2-10 minutes
What is a normal D-Dimer level?
< 500 mg/mL
What are differential diagnoses for elevated D-Dimer?
DVT
PE
DIC
What is the mechanism of action of heparin?
Binds to antithrombin (a natural circulating anticoagulant) and enhances its anticoagulant ability 1,000 fold
The heparin-AT complex neutralizes thrombin and activated factors 9, 10, 11, and 12
Platelet function also inhibited
Discuss heparin dosing and therapeutic levels:
cardiac surgical dose: 300-400 U/kg
VTE prophylaxis: 5,000 U SC BID or TID
Active VTE dose: 5,000 U IV, infusion ~1,250 U/hr - maintain aPTT 1.5-2.5 times normal
Unstable angina and acute MI dose: 5,000 U IV, infusion 1,000 U/hr
therapeutic aPTT: 1.5-2.5 times normal (normal 25-35 seconds)
ACT on CPB: > 400 seconds
Where is endogenous heparin produced?
liver
basophils
mast cells
How does warfarin work?
Inhibited Vitamin K epoxide reductase complex 1 (an enzyme).
This indirectly inhibits production of vitamin K dependent factors 2, 7, 9, 10 and Proteins C and S
