Anti-Coagulants Flashcards
Function
Stop further blood clots from developing on top of already formed clots
Name 2 conditions where anti-coagulants are indicated
AF
Venous thrombosis
In AF, thrombus formed in wall of LA can break off to form an embolus and travel through the circulation until it often lodges in which location?
Carotid arteries
Patients with AF must take anticoagulants for short term/long term?
Long term
- for life
If patient develops their FIRST venous thrombosis, for how long are anti-coagulants required
6 months
If patient has a Hx of venous thrombosis and then develops another DVT, how long are anti-coagulants required?
For life
What do anti-coagulants target?
Formation of the fibrin clot
Name 3 naturally occurring anticoagulants
Antithrombin
Protein C+S
Which naturally occurring anticoagulant(s) falls in the first week of warfarin therapy?
Protein C+S
Why is warfarin not a good immediate choice for an acute clot?
causes a decrease in naturally occurring anticoagulants protein C+S for the first week of therapy
Which anticoagulant is used in the acute setting as it has an immediate effect?
Heparin
What medication is used first line for acute thrombosis?
Heparin
Heparin - routes of administration
IV
SC
Heparin - mechanism of action
Potentiates anti-thrombin
Name 2 forms of heparin
Unfractionated
LMWH
What is used more often?
- LMWH
- unfractionated heparin
LMWH
LMWH route of administration
SC
LMWH - mechanism of action
When antithrombin (natural) binds to factor Xa, LMWH binds to it to ensure that clotting factors remain switched off
How do you monitor unfractionated heparin ?
APTT
How do you monitor LMWH ?
Factor Xa assay
Bear in mind that usually no monitoring is required for LMWH
Complications of heparin (3)
Bleeding Autoimmune phenomenon - HITT (heparin induced thrombocytopenia with thrombosis) Osteoporosis - with long term use
Patient on heparin gets regular FBC check ups and nurse notices that the platelet count has suddenly dropped. What does this suggest?
Autoimmune phenomenon
- platelets have stuck together to form blood clots
Heparin half life?
30 mins
Heparin reversal
Stop heparin
Antidote - protamine sulphate
What is the antidote for heparin
Protamine sulphate
Protamine sulphate completely/partially reverses unfractionated heparin
Completely
Protamine sulphate completely/partially reverses LMWH
Partially
What is used more commonly?
- LMWH
- unfractionated heparin
LMWH
When would unfractionated heparin be used?
Patient presents with acute thrombosis and you need to anticoagulant IMMEDIATELY
- pregnant lady about to give birth
- pre surgery
What is warfarin metabolised by
Cytochrome P450
Warfarin - mechanism
Vitamin K antagonist (inhibition of vitamin K)
Blocks the ability of it K to carboxylate the bit K dependent clotting factors (II, VII, IX, X) thereby reducing their coagulant activity
Warfarin - monitoring
PT
INR
Warfarin - aim for INR range of
2-3
What are the 4 vitamin K dependent clotting factors
II, VII, IX, X
Warfarin - complications
Bleeding
Warfarin - reversal - if mild (bruising, epistaxis)
No action required
Warfarin - reversal - high INR
Vitamin K
How long does vitamin K take to bring the INR back down to normal range?
6 hours
Warfarin - reversal - if life threatening haemorrhage
Administer clotting factors
How long does administering clotting factors take to bring the INR back down to normal range?
Does it immediately
Why is administering clotting factors for warfarin reversal not done routinely
You expose the patient to many donor blood pools
Name 2 types of new anticoagulants
Direct thrombin inhibitors
Xa inhibitors
Warfarin - safe to use in pregnancy. True or false?
False
- teratogenic
Warfarin - administration route
Oral
New anticoagulants - administration route
Oral
New anticoagulants - is there an antidote for reversal?
No
When are new anticoagulants used
As prophylaxis in elective hip and knee replacement surgery
New anticoagulants - thrombin inhibitors - example
Dabigatran
New anticoagulants - Xa inhibitors - examples
RivaroXaban
ApiXaban
