Anticoagulation Flashcards
What are injectable anticoagulants?
Unfractionated heparin
LMWH (enoxaparin, tinzaparin)
Activate antithrombin III
What does antithrombin do?
Inactivtes some clotting factors and thrombin by complexing with series protease of the factors
When are heparins used?
Immediate action
Used to prevent thrombosis (venous unstable angina) and used to prevent blood clotting on collection
Used whilst warfarin takes effect
Unfractioned heparins monitored via APTT
How do you monitor unfractionated heparin?
Activated partial thromboplastin time (APTT)
Don’t need coagulation monitoring
Platelets: >5 days heparin can lead to thrombocytopenia
How is a DVT diagnosed?
Painful swelling in calf
USS
Blood test- increased levels of D-dimer
What is D-dimer?
Product of fibrinolysis and is raised in thrombosis
What are risk factors for DVT/PE?
Surgery Pregnancy Oestrogens Malignancy MI/heart failure Obesity Age >40 Coagulation disorders Immobility Past history of VTE Trauma
What is warfarin?
Oral anticoagulant
Vitamin K antagonist
Vitamin K essential for production of prothrombin and factors VII, IX and X
Warfarin blocks vitamin K reductase, needed for fit K to act as a cofactor
Which patients is warfarin used in?
Replaced heart valves
AF
PE
DVT
What is prothrombin time?
Time for coagulation following addition of thromboplastin
Prolonged by abnormalities of factors VII, X, V, II or I
How is warfarin monitored?
Monitored by INR (prothrombin time) with a specific target value and the dose is adjusted
Normal INRs are around 1
INR is increased by impaired clotting due to warfarin and liver disease (as the liver produced coagulation factors)
What do increased actions of INR lead to?
Bleeding: Gastric Cerebral Haemoptysis Blood in faeces Blood in urine Easy bruising
How often should INR be monitored when using warfarin?
2x per week then increase interval gradually (max interval is 12 weeks)
Why is warfarin be reversed?
Reversed with vitamin K
If patient is bleeding
Has a very high INR (>8-10)
Warfarin overdose
What counselling is given to patients when taking warfarin?
Take at 6pm
If they miss a dose they should not take 2 doses together and should inform doctor at the next blood test
Inform a HCP they are taking it
Advise young women not to become pregnant
Alcohol may be consumed in moderation
How should patients change their diet whilst on warfarin?
Avoid excessive consumption of green vegetables (particularly spinach, Brussel sprouts, letuce, broccoli) and beetroot and liver
Changes to diets rich in vitamin K should be discussed with a HCP, as a change of warfarin may be required
What should patients report when taking warfarin?
Haemoptysis Blood in faeces Blood in urine Nose bleeds (>20-30 mins) Easy bruising Skin changes (necrosis) Consult doctor if they have diarrhoea or vomiting for 2 days or more
How does pregnancy affect coagulation?
Produces a thrombophilic state in the mother
Prevents post partum haemorrhage
Thrombophilia, decreased venous return due to the gravid uterus and immobility during labour
Mothers with artificial heart valves?
Why should you avoid warfarin in pregnancy?
Teratogenic Chondroplasia punctata (altered bone growth) Optic atrophy Mental retardation Avoid in trimester 1 and 3 Favour LMWHs
What should you give patients who need immediate anticoagulation?
Heparin
Warfarin is delayed- 3 days
What is dabigatran?
Oral thrombin inhibitor Prevents thromboembolism Less bleeding than warfarin Fewer drug interactions Does not require monitoring
What’s rivaroxaban?
Oral inhibitor of activated factor X
The concurrent use of an enzyme inducer (rifampicin) does what in a patient taking warfarin?
Therapeutic failure
Plasma concentrations of warfarin are likely to be decreased
What is a contra-indication to thrombolytic (fibrinolytic drugs)?
Gastric ulcers
Risk of bleeding
