anticoagulants Flashcards
what are the benefits of warfarin?
can save a life from thrombo-embolism
AF patients have 60% reduction in strokes
what are the negatives in using anticoagulants?
- Frequent to causing preventable harm and admissions to hospitals
- Major cause of bleeding
- Major litigation (use or not use)
- Dose adjustments frequently required to avoid over or under anticoagulation
- rapid fall in protein C and S in first 2-3 days - increased risk of thrombosis on this time
what is the mode of action of warfarin?
prevents vit K promoted carboxylation of glutamic acid residues of factors I, VII, IX and X
prevents vit K dependent clotting factors
full anticoagulated in 48-72hrs
what do protein C and S do?
prevent blood clotting too much
what is INR?
internalised normalised range/ ratio
- standardised to reduce variation
based on patients on variation
- way to measure patients warfarin levels
what is contra-indicated with warfarin?
- Avoid 48hrs post partrum
- Haemorrhagic stroke
- Significant bleeding
- Known coagulation defects
- Excessive alcohol intake
- Prone to falls
- Endocarditis
which group are high risk with warfarin?
pregnant women, elderly, end-stage renal disease, poor drug/ clinic compliance, CVS disease
what needs to be measured prior to starting warfarin?
- Prothrombin time – normal time for clotting
- Activated partial thromboplastin time (APTT) – time taken to clot with specific agents added
- Platelet count
- FBC
- Liver function test
- Baseline INR – should be 1
how many mg within the brown warfarin pill?
1mg
how many mg within the blue warfarin pill?
3mg
how many mg within the red warfarin?
5mg
what are the indications to warfarin?
- Prophylaxis of embolism in rheumatic HD +AF
- Prophylaxis after insertion of prosthetic heart valve
- Prophylaxis and treatment of venous thrombosis and PE
- TIA
what are side effects of warfarin?
bleeding, hypersensitivity, skin rashes, alopecia, diarrhoea, unexplained drop in haemocrit, jaundice, hepatic dsyfunction, purple toes, skin necrosis
what is the warfarin antedote?
vitamin K - phytomeandione
- stop taking warfarin may be more beneficial?
how many days prior to surgery would you stop taking warfarin?
5 days
if a patient requires antocoag before surgery, what would you do?
bridging - using LMWH as that can be used until 2hrs prior to surgery
what interacts with warfarin?
refer to BNF
alcohol
anything that increases bleeding risk - caution
oral contraceptive
st johns wort
cranberry/ grapefruit juice
other antiplatelets - use with caution
what is unfractionated heparin?
high molecular weight molecules, highly ionised
how must unfractionated heparin be administered?
not absorbed in GI
must be IV/ SC injection - gives high monitoring
which patients would benefit from unfractionated heparin the most?
high risk patients/ renal impairment - more in control and enough evidence
what do you monitor with a patient on unfractionated heparin?
trust protocol
prothrombin time, activated partial thromboplastin time
platelet count - HIT
FBC, liver function test
potassium
what is activated partial thromboplastin time?
time takes to clot with another agent present
what is HIT - platelet count
heparin induced thrombocytopenia - contra indicated with heparin
<80 need haematology referral
what is the antedote of unfrationated heparin?
protamine
what is the benefit of LMWH over warfain?
more predictable response
what is the action of LMWH?
indirect thrombin inhibitors
- enhance antothrombin II - inhibits thrombin IIa
- inactive factor Xa
how do you administer LMWH?
SC injection, dosage based on weight
what are the advantages of using LMWH over warfarin?
fixed dose, no labs, highly predictable plasma levels, higher bioavailability, ,longer half life - taken OD/ BD
what are the disadvantages of LMWH over warfarin?
more expensive
when would LMWH be best to use?
PE, DVT, thromboprophylaxis, daltaparin, tinzaparin
what is contra-indicated with LMWH?
all heparins, endocarditis, major trauma, epidural, avoid benzyl injections, peptic ulcer, thrombocytopenia
what is the antedote of LMWH?
can only be partially reversed
protamine
what are DOACs?
direct oral anticoagulants
name some DOACs?
dabigatran, rivaroxaban, apixaban, edoxaban
when are DOACs used?
non-valvular AF, DVT, PE - treatment and prophylaxis of current VTE
rivaroxaban also has other uses other DOACs do not, what are they?
prophylaxis of atheromatic events following ACS with elevated cardiac biomarkers
- can be taken with/ without aspirin
what is the action of DOACs?
prevents prothrombin to thrombin pathway
acts on Xa factor
what are the benefits of DOACs?
no INR monitoring, predictable anticoag reponse, rapid onset (1-4hrs), lower risk of bleeding, including intracranial.
stroke protection equivalent to warfarin
- can go in compliance aids (dosage boxes), can be crushed
what is the new first line anticoagulant?
DOACs
what is contra -indicated with DOACs?
lesion/ condition that can increase bleeding risk significantly
- current/ recent GI ulcer
presence of malignant neoplasm
recent brain/ spinal surgery, intercranial haemorrhage
vascular aneurysms/ major intraspinal abnormalities
WITH ANY OTHER ANTICOAGULANTS
what needs to be checked prior to starting DOACs?
check interactions
age, weight
renal function
what should rivaroxaban be taken with?
food - increases bioavailability
what are side effects of DOACs?
GI disturbances, pain, dsypesia, altered liver function, rash/ pruritis, epitaxis, bruising, small haemorrhages
what side effects are common to rivaroxaban?
dizziness, may affect ability to drive, tachycardia, dry cough
what does CHA2DS2-VASc do?
assess stroke risk following AF
what is HAS-BLED used for?
bleeding risk score system on anticoagulants
what is ORBIT?
bleeding risk score system for those who had AF
- used more commonly in practice
