Hematology/Oncology Flashcards
1
Q
What is the mechanism of heparin in anti-coagulation?
A
- antithrombin mediated inactivation
- heparin binds antithrombin (aka antithrombin III) which increases its activity
- irreversibly binds Xa, thrombin (IIa) = inhibits coagulation activity
2
Q
Draw the coagulation cascade.
Label the intrinsic and extrinsic pathways. PTT v PT?
A
See notes.
3
Q
What labs are used to monitor heparin activity?
A
PTT
anti-Xa assay
4
Q
What are the primary causes for heparin resistance in neonates?
A
- inadequate concentrations of antithrombin
- increased clearance of heparin
- increased binding of heparin to plasma proteins (can’t exert effect)
- increased concentration of fibrinogen or factor VIII
5
Q
Heparin activity is directly related to…
A
-amount of antithrombin III available
6
Q
What are the mechanisms of heparin clearance?
A
- binds to epithelial cells, macrophages; internalizes/degrades
- renal clearance (faster in neonates/preterm infants)
7
Q
Why do neonates require higher rates of heparin infusion?
A
-faster renal clearance
8
Q
Does the fetus produce endogenous clotting factors?
A
YES - maternal factors do not cross the placenta
- @5-10 wks gestation: measurable levels, increase throughout gestation
- @6 months: comparable to adult levels
9
Q
Which factors are Vitamin K dependent?
A
II, VII, IX, X
