Warfarin Flashcards
When is warfarin used for INR range 2-3? (incl. time frames)
DVT: 3-6 months
PE: 6 months
AF: until risk > benefit
When is warfarin used for INR range 2.5-4.5?
Mechanical prosthetic valves (high risk)
patients with recurrent thromboses / warfarin
thrombosis associated with inherited thrombophilia conditions (hypercoagulibility)
What are other uses of warfarim?
cardiac thrombus
CVA especially with AF
cardiaomyopathy (walls thick / stenosed)
Adverse effects of warfarin?
bleeding / bruising
teratogenic
where are sites of bleeding / bruising from warfarin?
intracranial
epistaxis, injection, GI loss
what are the risks of warfarin in a woman of child bearing age?
risk of pregnancy due to indications with COCP (CYP450)
as well as being teratogenic
What are reversal therapies for warfarin?
parental vitamin K
fresh frozen plasma
prothrombin complex concentration
why is fresh frozen plasma preferred over vitamin K?
faster acting, contains active clotting factors
when is fresh frozen plasma given?
in severe bleeding
indications for initiation of treatment in PMH?
peptic ulcer disease
sub-arachnoid haemorrhage
bleeding disorders
previous stroke
what are reviews required before commencing treatment?
age
mobility (blood tests)
falls risk score (bleeding from falls > condition you’re trying to treat) : CHADS2-VASC & HAS-BLED
what are investigations required before commencing treatment?
review blood tests:
LFTs, platelet levels, INR (baseline)
what is required in the initiation of warfarin as a treatment regime?
consider loading dose to take treatment up to therapeutic window
use heparin to cover for the initial 3 days until warfarin starts working
why does it take warfarin a few days to work?
warfarin inhibits vitamin K synthesised proteins (protein C & S, clotting factors 2, 7, 9, 10) so have to wait until those proteins are completely used up / out of the system
what are the interactions of warfarin?
alcohol, cranberry / grapefruit juice
they are inhibitors of CYP450, so warfarin NOT metabolised, so warfarin concentration builds up
What should you give patients started on warfarin?
anticoagulated card
what is prothrombin complex concentrate (PCC)?
factor IX complex
made of clotting factors 2, 7, 9, 10
why is fresh frozen plasma good for rapid bleeds?
contains active clotting factors
when else is warfarin reversal given?
elective surgery: don’t want excessive bleeding during surgery
(non-emergency)
when is IV vitamin K used?
not for serious bleeds
takes a few days to work
what is the management of INR <6?
reduce warfarin / stop
when do you restart warfarin?
when INR < 5
what is the management of INR 6-8? (with no or minor bleeding)
stop warfarin
restart when INR < 5
what is the management of INR >8? (with no or minor bleeding)
stop warfarin
consider 0.5-2.5mg vitamin K (oral)
