Clotting Cascade Flashcards
Action of Warfarin
Decreases the amount of active vit K, which is required by y-glutamylcarboxylase, due to its ability to inhibit epoxide hydrolase.
y-glutamylcarboxylase is required in the synthesis of Ca2+ binding proteins, which are (6)
Factors II, VII, IX, X
Protein C
Protein S
Extrinsic clotting pathway (2)
Activated by external trauma.
Quicker than the intrinsic pathway.
Intrinsic clotting pathway (3)
Activated by trauma inside the vasculature.
Activated by platelets, exposed epithelium, collagen.
Slower that extrinsic pw.
Draw the Intrinsic PW
See notes.
Draw the Extrinsic PW
See notes.
Primary hemostasis
Platelets in blood aggregate at tissue site and form a plug.
Secondary hemostasis
Platelet plug is reinforced by fibrin mesh through a coagulation cascade.
Major roles of Thrombin (5)
Convert prothrombin to thrombin. Convert V and VIII to Va and VIIIa. Convert fibrinogen to fibrin. Activate platelets. Convert XIII to XIIIa cross linked fibrin.
2 types of oral anticoagulants
Hydroxycoumarins
Indanediones
Long term control of INR requires:
Vitamin K
Daily oral vitamin K requirements:
50-100 mg
Vitamin K activation cycle
Draw
What enzyme is the target for warfarin?
Vitamin K epoxide reductase (VKOR)
Now cannot activate factor II, VII, IX, X and Protein C or S.
Warfarin exists in a _________ and the _____ is more predominant
Racemic mixture
S form
Warfarin has a high degree of ___________
Drug interactions. Must take them into consideration.
Main roles of protein S and C (2)
Maintain vascular permeability.
Inactivates factor Va and factor VIIIa.
A genetic deficiency in protein C increases the risk of:
Venous thrombosis.
Recommendations for patients taking coumadin
Check meds Check INR Watch for signs of bleeding Stomach pain, ulcers, fever, nausea are common side effects. Carry an ID card. Watch diet.
Hemophilia A is a deficiency in what?
Factor VIII
PT measures
PTT measures
Extrinsic pathway
Intrinsic pathway
Factor with the shortest half-life
Factor VII
End-stage liver disease’s affect on PT and PTT
Tends to increase PT before PTT due to deficient production of factor VII.
ISI
Reference values
International sensitivity index.
Indicates how a particular batch of tissue factor compares to an international reference tissue factor.
Usually between 0.94 and 1.4 for more sensitive and 2.0-3.0 for less sensitive preps.
INR
Ratio of a patient’s prothrombin time to a normal sample raised to the power of the ISI value.
