Anticoagulation Flashcards
What does a DVT present as?
Usually presents as swollen, hot, red and painful leg (although can occur in other parts of the body).
How do we determine the probability of a DVT?
Use wells DVT criteria:
Active cancer - 1
Paralysis, paresis or recent plaster - 1
Recently bedridden and/or major surgery - 1
Localised tenderness along the distribution of the deep vein system - 1
Entire leg swollen - 1
Calf swelling >3cm more than asymptomatic side - 1
Pitting oedema - 1
collateral superficial veins - 1
Alternative diagnosis - 1
What is a D-dimer test? Is it specific?
A positive D-dimer indicates the presence of an abnormally high level of cross-linked fibrin degradation products in your body. It tells your doctor that there has been significant clot (thrombus) formation and breakdown in the body, but it does not identify the location or cause.
Any source of inflammation/infection can increase D-dimer not specific.
If a patient has a low probability score, following wells criteria what do you do?
D-dimer test
If a patient has a moderate or high probability score following wells criteria what do you do?
US - ultrasynography (color duplex scan)
D-dimer test
How do we determine the probability of a PE?
PE wells criteria
If a patient has a moderate-high probability of PE what do we do?
CTPA scan (CT pulmonary angiography)
When might we use UFH?
In situations where it is useful to have a rapid on-off effect (as short half life, hence why given IV)
Renal impairment
What are the complications associated with UFH use?
under/over dosage is common
Osteoporosis risk is higher compared to LMWH
Heparin-induced thrombocytopenia (HIT)
What is the MOA of warfarin?
Vitamin K antagonists.
Vitamin K epoxide reductase inhibitor
What is the INR target with warfarin?
2-3
What side effects are associated with warfarin?
bleeding, alopecia, skin rashes
Can warfarin be used in pregnancy?
No - teratogenic in the first semester, switch patient to LMWH
Management of warfarin overdose - in a patient with INR 6-8 with no bleeding?
Stop warfarin and restart when INR <5.0
Management of warfarin overdose - in a patient with INR >8 and no bleeding what do you do?
Stop warfarin and restart when INR <5.0
0.5-2/5mg of vit K oral or IV
Management of warfarin overdose - what do you do in major bleeding?
Stop warfarin
Give prothrombin complex concentrate (PCC) 50U/kg
Give vit K 5mg oral or IV - give IV for higher INR values
Why don’t we want to give too high doses of vitamin K in the management of warfarin overdose?
Can cause resistance to subsequent anticoagulation.
What anticoagulant should be used in patients if CrCl < 15?
Warfarin
What anticoagulant should be used in patients if CrCl 15-30
Apixaban or rivaroxaban
What anticoagulant should be used in children?
Warfarin
What anticoagulant should be used in heart valve prosthesis?
Warfarin
What anticoagulant should be used in patients with a high bleed risk?
Warfarin or apixaban
What anticoagulant should be used in patients with CAD, previous MI or a high risk?
Rivaroxaban shoudl be considered - agent has a postiive effect in ACS
What baseline monitoring is required before starting UFH?
INR, APTT and platelet count.
How are LMWH doses decided?
Weight and renal function.
What dose of LMWH is required for a patient weighing <50kg for VTE prophylaxis?
2500 U s/c OD
What dose of LMWH is required for a patient weighing 50-100kg for VTE prophylaxis?
5000 U OD
What dose of LMWH is required for a patient weighing 100-150kg for VTE prophylaxis?
5000U BD
What dose of LMWH is required for a patient weighing >150kg for VTE prophylaxis?
7500 U BD
Might even require higher doses!
What is the standard loading dose for warfarin? what factors might require a lower dose?
Loading dose is usually 10mg daily for 2 days - this is based on a 70kg patient with no co-mordities
May want to lower the dose if there is an increased risk of bleeding, elderly patients and those with impaired liver function.
What is beriplex?
Pro thrombin complex concentrate, used for emergency reversal of warfarin
What does apixaban inhibit?
A direct inhibitor of activator factor X (Xa)
What does rivaroxaban inhibit?
A direct inhibitor of activator factor X (Xa)
What monitoring does dabigatran require?
Renal function
What does dabigatran inhibit?
Direct thrombin inhibitor
What problems are associated with dabigatran?
Relatively large tablets
Must be stored in original packaging - should not be added to multi-compartment compliance aids.
Dexterity required to remove from packaging
In terms of missed doses, how might the impact of this vary between NOACs and warfarin?
The NOACs have short half lives (less than 24 hours) compared with warfarin (about 37 hours).
Which of the NOACS might be preferred in patients who do not want to take multiple tablets?
Rivaroxaban is once daily
All patients who are started on warfarin or a NOAC should be given what?
All patients should be given an anticoagulant card.
What are the differences between the arterial and venous processes involved in thrombus formation?
Venous thromboembolism is generally as a result of poor blood flow, which may be as a result of immobility, concurrent medication, dehydration, or vascular injury and generally results in deep vein thrombosis or pulmonary embolism.
Arterial thromboembolism, although often a result of hypercoagulability and vascular injury, results most commonly in myocardial infarction, ischaemic stroke or TIA.
Give some examples of acquired prothrombotic risk factors
COC HRT Smoking Long haul travel over 4 hours Obesity - BMI over 30kg/m2 Previous history VTE High cholesterol levels Co-morbidities - cancer, CVD Pregnancy Surgery
What monitoring is required with LMWH?
Baseline FBC, U&Es, LFTs and clotting screen.
Body weight and renal function to determine dose.
Monitor for hyperkalemia
Platelet counts after 4 days and throughout treatment
How often is INR monitoring required with warfarin?
INR daily/alternate days in early treatment, then increase up to every 12 weeks.
What is idarucizmab?
Dabigatran reversal agent
How can we treat LMWH and UFH overdose?
Protamine sulfate is used to treat overdosage of UFH and LWMH
The long half-life of LMWH should be taken into consideration when determining the dose of protamine sulfate
What is the normal range for the respiratory rate?
12-25
What possible differential diagnoses need to be considered in a patient presenting with symptoms of a PE?
Chest infection, cellulitis, MI
Why are high doses of LMWH heparin split?
High single doses are associated with an increased bleed risk.
When would we consider an anti Xa test for LMWH monitoring?
Only in special cases - children, renal impairment, extremes of weight.
Can LWMH be given in pregnancy?
Yes - does not cross the placenta.
How do we dose LMWH in pregnancy?
doses are given TWICE daily (due to PK changes)
Based on pre-pregnancy or early pregnancy weight.
How long is anticoagulation treatment continued in pregnant patients with a DVT?
Standard treatment is 3-6 months, must continue for 6-12 weeks post-partum.
How should a pregnant women taking LMWH be managed when she
a) goes into labour
b) post partum
Treatment should be stopped at the onset of labour or if patient is having a planned casarean then it should be stopped the day before.
Post partum - depending on the circumstances and bleed risk, we normally restart in 12 hours. Go back to once daily doses!
Manage at home with either LMWH or warfarin
What contraceptive advice would you give a women with a previous history of VTE?
Cannot give oestrogen containing contraceptives (COC)
Options are - POP, IUD, progesterone implant
How do you manage VTE risk in a patient in their second pregnancy who has a VTE in their prior pregnancy?
Prevention LMWH should be started 4 weeks before the VTE occured in the first pregnancy.
Anti embolism stockings as soon as pregnant.
Is LMWH safe in pregnancy?
Yes