Venous Thromboembolism Flashcards
How many people have a VTE in their lifetime?
1 in 20
What drugs can contribute to an increased risk of VTE
HRT
contraception
tamoxifen
thalidomide
VTE assessment should be done
- within 24 hours of admission
- if their condition changed
- VTE proph should be prescribed within 24 hours if needed
What sort of medicine should be stopped if a patient is having a CTPA scan with contrast media?
metformin due to the risk of contrast induced nephropathy
What is a two-level DVT/PE wells score
It estimates the probability of a DVT using clinical features e.g. active cancer, bed ridden, localised tenderness, previous DVT. If a score is > 2 then a DVT is likely. This is not completely accurate so has to be confirmed using a proximal leg ultrasound and a d-dimer.
People with suspected PE should undergo immediate CT
How many hours post dose should factor Xa levels be taken?
4 hours
When can patients have thrombolysis with a PE?
When they have a ‘massive PE; associated with haemodynamic instability. This is often carried out in CCU or ITU
When would a patient have life-long anticoagulation?
If they have an unprovoked PE/DVT
How to unfractionated heparins work?
They are a mixture of large mucopolysaccharides that increase the interaction between thrombin and anti-thrombin III swell as preventing the conversion of fibrinogen to fibrin.
They have a short half like and require administration via a continuous infusion when treating a VTE
They are out of favour now compared to LMWH however may be used in bridging for a patient having a heart valve replacement who cannot have their warfarin with having surgery
Main side effects of heparins?
-HIT
-this is an immune mediated reaction.
It usually developed 5-10 days after initiation (range 4-15 days) and is usually seen by a 30-50% reduction in platelets.
-This can be stopped and switched to a non-heparin anticoagulant such as fondaparinux or danaparoid
-Always contact haem for advice.
It can also cause hyperkalaemia via inhibition of aldosterone synthesis
Long term use may cause osteoporosis
List vitamin K agonist (coumarin drugs)
warfarin
acenocoumarol
phenindione
is monitoring of warfarin phrarmodynamic or pharmokinetic
pharmodynamic
How does warfarin work?
It is a citation K antagonist, which reduces the hepatic production of vitamin K dependent active coagulation factors II, VII, IX and X along with the regulatory anticoagulant proteins C and S in a dose related way.
This action results in prolongation of the prothrombin time (bleeding time) and a decreased tendency to form blood clots.
Warfarin therefore prevents enlargement of existing blood clots and formation of new blood clots.
INR means
international Normalised Ratio
In what circumstances would we expect a higher INR?
- recurrent VTE whilst a patient is on warfarin
- mechanical valve
How long would a patient be on anticoagulation for if they had a provoked PE?
3 months and then review (based on chadsvasc and hasbled)
In which situations would a patient be on life long anticoagulation?
- AF
- mechanical valve
- unprovoked recurrent VTE
What is classed as poor INR control?
- Two INR readings greater than 5 or one greater than 8 in the last 6 months
- Two INR readings less than 1.5 in the past 6 months
- Time in therapeutic range (TTR) less than 65%
We would review and consider changing to a DOAC in this situation
How long does warfarin take to anticoagulant fully?
72-96 hours
Drugs to avoid with warfarin
- aspirin
- miconazole
- NSAIDS
- enteral feeds containing vit K
All others we can consider a dose adjustment or monitor INR - look at page on canvas
what do we do in a high INR
if INR is 5-8 stopping the warfarin usually suffices.
If INR >8 then we would give vit K even if patient is not bleeding
What are DOACS licensed for ?
- prevention of VTE post knee/hip surgery
- treatment of VTE
- stroke prevention in non-valvular AF (N.B. warfarin can be used in valvular AF)
Which DOAC cannot be used in eGFR <30ml/min
dabigatran
- it is 80% excreted by the kidneys
Which DOAC needs to be taken with food?
Rivaroxaban
