Anticoagulants Flashcards
which type of blood vessels do anticoagulants mainly work in
They work in slower-moving veins where a thrombus is made of fibrin, platelets + red blood cells. They are less useful in arteries because they are faster-flowing and a thrombus would be made of platelets + little fibrin
note: fibrin is a major component of a blood clot. Anticoagulants target fibrin
when should patients taking anticoagulants seek immediate medical attention
- bleeding that is severe
- bleeding that does not stop or recurs
- who have other signs or symptoms of concern (e.g. sudden severe back pain or breathlessness)
- patients who have sustained a head injury should be referred to the hospital emergency department
how do vitamin k antagonists work as anticoagulants?
name some examples of vitamin-k anticoagulants
They inhibit the formation of the active form of vitamin K which is needed for clotting factors involved in coagulation.
examples of vitamin-K anticoagulants:
- warfarin (drug of choice)
- acenocoumarol
- phenindione
how long does it take for the full anticoagulant effect of vitamin-K antagonists to develop
at least 48-72 hours
what drug is given if a patient needs an immediate anticoagulant effect but is taking vitamin - k antagonists
vitamin k antagonists anticoagulant effect takes at least 48-72 hours for full effect.
Must give unfractionated or low molecular weight heparin alongside if immediate anticoagulant effect is needed,
what is the preferred drug for prophylaxis of venous thromboembolism in patients undergoing surgery
unfractionated or low weight heparin
note warfarin can be used instead for this if a patient has been taking warfarin for a long time and they’re at high risk for thromboembolism. (seek expert advice for this)
when might warfarin be used in prophylaxis of venous thromboembolism in patients undergoing surgery
in selected patients that have been taking warfarin long-term and they are at risk for thromboembolism. (seek expert advice for this)
what is the base-line prothrombin time and when should it be taken
prothrombin time measures the time it takes for your blood to clot.
it should be taken before treatment (base-line) but treatment with an anticoagulant should not be delayed whilst waiting for result
what does INR mean
INR= international normalized ratio (INR). It is how the prothrombin time is expressed.
Prothrombin time= the time it takes for your blood to clot
when would you deem an INR result as satisfactory
if it is within 0.5 units of the target value.
note larger deviations from target value than this mean the dose needs to be adjusted
what is the recommended time a patient should be taking warfarin for isolated calf-vein deep-vein thrombosis
6 weeks
what is the main adverse effect of all oral anticoagulants
haemorrhage (bleeding)
what should you do if an anticoagulant is stopped but not reversed
keep monitoring patient to measure the INR every 2-3 days to make sure the INR is falling.
Investigate why INR is elevated
what is NOT recommended for emergency anticoagulation reversal in patients taking warfarin
recombinant factor VIIa
which patients are considered high risk of thromboembolism prior to surgery
Those with:
- venous thromboembolic event within the last 3 months - - atrial fibrillation with previous stroke or transient ischaemic attack
- mitral mechanical heart valve
if a surgery carries a high risk of bleeding + a patient was given low weight molecular heparin. When would you consider restarting the low weight molecular heparin
at least 48 hours after surgery
when might a patient be on combined antiplatelet and anticoagulant therapy
name an example of the combined therapy
following an acute coronary syndrome or percutaneous coronary intervention (PCI)
e.g aspirin + warfarin, warfarin + clopidogrel, aspirin + warfarin + clopidogrel (triple therapy)
which carries a higher risk of bleeding:
aspirin + warfarin or clopidogrel + warfarin
clopidogrel + warfarin
what is a DOAC
name the 4 examples
direct-acting oral anticoagulant
examples: apixaban, dabigatran etexilate, rivaroxaban, edoxaban
What is the mechanism of action of dabigatran etexilate as a DOAC
it is a reversible competitive inhibitor that inhibits thrombin (a clotting factor) from converting fibrinogen to fibrin. Fibrin molecules normally combine platelets together to form blood clots (platelets aggregation) dabigatran etexilate prevents this from happening. This is known as thrombin-induced platelet aggregation.
what is the mechanism of action of Apixaban, edoxaban, and rivaroxaban as DOACs
they are reversible inhibitors of activated factor X (factor Xa) which prevents thrombin generation and thrombus development.
less/no thrombin generated = less/no fibrinogen converted to fibrin so less/no platelets combined together to form blood clots (platelet aggregation)
name some indications for the use of all DOACs: Apixaban, dabigatran etexilate, edoxaban, and rivaroxaban
- prevention of stroke
- prevent systemic embolism in patients with non-valvular atrial fibrillation
- secondary prevention of deep-vein thrombosis and/or pulmonary embolism
which DOACs are used for prevention of venous thromboembolism after elective hip or knee replacement surgery
Apixaban, dabigatran etexilate, and rivaroxaban
all of them apart from edoxaban
what is the use of rivaroxaban
- prevention of atherothrombotic events in patients with coronary or peripheral artery disease
- acute coronary syndrome with raised biomarkers
note this is part of secondary prevention of cardiovascular events
What monitoring do you need for DOACs
do they need regular anticoagulation monitoring
monitor for signs or bleeding or anemia (stop treatment if severe bleeding occurs)
No they don’t need regular anticoagulation monitoring
how long does it take for the anticoagulant effect of DOACS to stop
what is the consequence of this
12-24 hours after the last dose was taken
consequence: if a patient misses or delays a dose, it can have a reduction in the anticoagulant effect
what drug can reverse the anticoagulant effect of dabigatran etexilate
Idarucizumab
it can be used in life-threatening/ uncontrolled bleeding, emergency surgery/ urgent procedures
what drug can reverse the anticoagulant effect of apixaban or rivaroxaban
Andexanet alfa
it can be used in life-threatening/ uncontrolled bleeding
how do you switch a patient from warfarin to a DOAC
- stop warfarin treatment before starting DOAC.
this is to reduce risk of over-anticoagulation + risk of bleeding
when should a woman postpartum start taking warfarin again
delay warfarin until risk of bleeding is low (usually 5-7 days after birth delivery)
what does it mean if your INR is too high (higher than target INR)
if the INR is too high, it means your blood is taking longer to clot so you are at increased risk of bleeding
what does it mean if your INR is too low (lower than target INR)
if the INR is too low, it means your blood is clotting quicker so you are at increased risk of a blood clot
why should pregnant women avoid taking vitamin k antagonists in their first + third trimester
because all vitamin k antagonists are teratogenic. highest risk is in the 1st + 3rd trimester
when is it advised that pregnant women stop taking vitamin k antagonists
stop vitamin k antagonists before the 6th week of gestation to avoid fetal abnormalities
how often should patients on vitamin k antagonists have their INR monitoring
- baseline prothrombin time taken
name the contraindications for all DOACs
- antiphospholipid syndrome
- a lesion or condition if it is considered a risk factor to major bleeding
- concomitant use with any other anticoagulant
- previous stroke/ TIA (when indication is for prophylaxis of atherothrombotic events)
can you take any other anticoagulant when taking a DOAC
No, must not use any other anticoagulants when taking a DOAC unless you are switching therapy when unfractionated heparin is given
TRUE OR FALSE
Rivaroxaban should not be used in patients with prosthetic heart valves, including patients who have undergone transcatheter aortic valve replacement (TAVR)
TRUE
this is because there is an increased risk of all-cause death and bleeding
which has an increased risk of recurrent thrombotic events in patients with antiphospholipid syndrome:
- vitamin k antagonists
- DOACs
DOACs
DOACs are not recommended in patients with antiphosholipid syndrome. If a patient is on a DOAC with antiphospholipid syndrome, consider switching them to a vitamin K antagonist
why should you take rivaroxaban with food
because taking rivaroxaban with food increases the efficacy compared to taking it on an empty stomach
note in those who have difficulty swallowing, can crush tablets mixed with water/apple puree then eat food immediately after
can you use DOACs whilst pregnant or breastfeeding
no, manufacturer advises to avoid in pregnancy (toxicity seen in animals) + breastfeeding (present in breast milk)
what is the difference between standard/unfractionated heparin vs low molecular weight heparins
standard/unfractionated heparin initiates anticoagulation rapidly but has a short duration of action whereas
low molecular weight heparin has a longer duration of action
note low weight heparin is generally preferred
although low weight heparin is usually preferred to unfractionated/standard heparin, why might unfractionated/standard heparin still be used
because the anticoagulant effect of unfractionated/standard heparin can quickly be stopped by stopping the infusion (due to short duration of action*
note low weight heparin has a longer duration of action
name some examples of low weight heparins
they end in “rin”
- enoxaparin sodium
- dalteparin sodium
- tinzaparin sodium
what low weight heparins used for
- preventing venous thromboembolism (VTE)
- treating deep vein thrombosis (DVT) and pulmonary embolism
which type of heparin has a lower risk of causing heparin-induced thrombocytopenia
low weight heparins
name some examples of parenteral anticoagulants
- low weight heparin + unfractionated/standard heparin
- Bivalirudin (used in NSTEMI or unstable angina patients as an anticoagulant for percutaneous coronary intervention)
- Epoprostenol (prostacyclin). Also a potent vasodilator used in primary pulmonary hypertension resistant to other treatment
- Danaparoid sodium
- Argatroban
- Fondaparinux
what is Venous thromboembolism (VTE)
includes both deep-vein thrombosis (DVT) and pulmonary embolism (PE), and refers to a blood clot that forms in a vein which partially or completely obstructs blood flow
what is Hospital-acquired venous thromboembolism (VTE)
VTE that happens within 90 days of hospital admission
name some risk factors for Venous thromboembolism (VTE)
- surgery/trauma
- significant immobility
- obesity
- pregnancy and the postpartum period
- hormonal therapy (combined hormonal contraception or hormone replacement therapy)
- acquired or inherited hypercoagulable states (blood which has increased tendency to clot)
where does deep vein thrombosis (DVT) normally occur
what are the symptoms
DVT normally occurs in deep veins of legs or pelvis but may affect other sites. It is the most common type of VTE
symptoms:
- localised pain/ tenderness
- swelling
- skin changes
- vein distension (bulging)
how does a pulmonary embolism (PE) normally occur
what are the symptoms
pulmonary embolism (PE) usually happens when a thrombus from DVT travels in the blood (embolus) and obstructs blood flow in the lungs. This causes respiratory dysfunction
symptoms:
- chest pain
- shortness of breath
- haemoptysis (coughing up blood)
TRUE OR FALSE
all patients should be assessed on their risk of venous thromboembolism (VTE) and bleeding on admission to hospital
True
describe the two methods of venous thromboembolism prophylaxis
- Mechanical: patients given anti-embolism stockings which provide a graduated pressure of 14-15 mmhg. They are worn day + night until patient is sufficiently mobile. or intermittent pneumatic compression device
- pharmacological: started at soon as possible or within 24hrs of admission. patients taking anticoagulants should only receive pharmacological treatment if anticoagulant therapy has been interrupted e.g for surgery.
which type of anesthesia (regional or general) should be used to reduce risk of VTE in patients
regional anaesthesia over general anaesthesia should be used if possible
which drug can be used all types of general and orthopaedic surgery as prophylaxis to prevent VTE
low molecular weight heparin
which drug is preferred as prophylaxis to prevent VTE in patients with renal impairment
unfractionated/ standard heparin preferred but can also use low weight molecular heparin
what is the first line treatment option to prevent VTE in medical patients (not at hospital for surgery)
first line is pharmacological treatment:
- low weight molecular heparin first line (fondaparinux sodium as an alternative), for a minimum of 7 days
which patients should NOT have mechanical treatment to prevent VTE
- acute stroke or those with conditions such as:
- peripheral arterial disease
- peripheral neuropathy
- severe leg oedema
- or local conditions (e.g. gangrene, dermatitis)
what are the 3 main drugs used in pharmacological prophylaxis of VTE in surgical patients
- low weight molecular heparin
- unfractionated/standard heparin
- Fondaparinux sodium
note patients may also be taking anticoagulants if undergoing elective hip/knee surgery
which drug is used for thromboprophylaxis in pregnancy
low weight molecular heparin
- elastic graduated compression stocking should be applied on the affected leg as an additional treatment to manage symptoms such as pain and swelling
- note this includes all pregnant women (who are not in active labour), or women who have given birth, had a miscarriage or termination of pregnancy during the past 6 weeks, with a risk of VTE that outweighs the risk of bleeding*
what are the drug treatment options for patients with confirmed DVT or pulmonary embolism
- first line= apixaban or rivaroxaban.
if not tolerated:
- low molecular weight heparin (LMWH) for at least 5 days followed by dabigatran etexilate or edoxaban; or
- LMWH + vitamin K antagonist for at least 5 days or until the INR is at least 2.0 for 2 consecutive readings, followed by a vitamin K antagonist on its own.
how do you reverse the anticoagulant effects of low molecular weight heparin or unfractionated heparin
- usually stopping the low weight heparin or unfractionated heparin is enough to reverse effects. If you need rapid reversal, use protamine sulfate (the antidote)
