Haematology Flashcards
LMWH are preferred in most clinical situations. When would you consider using UFH instead?
- Patients who might require their anticoagulation to be stopped rapidly e.g. high risk of bleeding or may require urgent invasive procedures. The half-life of UFH is dose dependent.
- Patients in severe renal failure: titration against APT is simpler than using LMWH and using anti-Xa levels.
Why are LMWH preferred over UFH?
They are as effective, have a lower risk of HIT, and the standard prophylactic regimen does not require monitoring. They also have a longer duration of action, which means that they are usually more convenient to use. In the longer term, they have a lower risk of osteoporosis.
How is warfarin started?
Warfarin is started at the same time as LMWH. LMWH needs to be continued for at least 5 days and until the INR has been in the therapeutic range for 2 consecutive days. LMWH is dosed by weight.
What is the difference between monitoring heparin and monitoring LMWH?
LMWH - factor Xa levels
Heparin - APTT
What are the side effects of heparin (and to a lesser extent, LMWH)?
Haemorrhage Heparin induced thrombocytopenia Hyperkalaemia Osteoporosis Alopecia Hypersensitivity reactions
How does fondaparinux work and when is it used?
It is a synthetic pentasaccharide that directs antithrombin to selectively inhibit factor Xa. It can be administered daily without laboratory monitoring and does not cause thrombocytopenia.
NICE has recommended fondaparinux as the antithrombin of choice in ACS.
How does warfarin work?
Warfarin antagonises the effects of vitamin K, which is a co-factor for factors II, VII, IX and X, as well as protein S and C. They take 48-72 hours to work, so for the treatment of thromboembolic disease, heparin should be given initially. There may be a paradoxical procoagulant effect of warfarin early on as it depletes anticoagulant effects more quickly than procoagulant factors.
What are the indications for warfarin?
Treatment of VTE
Stroke prevention in AF
Mechanical heart valves
How do the new oral anticoagulants work? How do they differ from warfarin?
Dabigatran - direct thrombin inhibitor, licenced for stroke prevention in AF and prevention of VTE.
Rivaroxaban and apixaban - direct inhibitors of factor X - licenced for AF, VTE treatment and prevention and PE treatment.
Compared to warfarin, they have a faster onset of action and do not require monitoring of INR. Unlike warfarin, there is not an effective method of reversing haemorrhage associated with these agents.
What are the side effects of aspirin?
Bleeding - including GI and intracranial
Exacerbation of asthma
Aspirin should not be given until hypertension is controlled to reduce risk of intracranial haemorrhage
How does clopidogrel work?
Thienopyridine compound that prevents platelet aggregation by selectively binding to adenylate cyclase-coupled adenosine diphosphate receptors
What are the adverse effects of clopidogrel?
Bleeding - risk increased when combined with aspirin
Dyspepsia, abdominal pain, diarrhoea
Efficacy may be reduced by omeprazole
What is the daily requirement of iron?
Approximately 1-2mg a day (3-4mg in pregnancy)
What are the side effects of ferrous sulphate?
GI side effects - nausea, diarrhoea, constipation - are most common and may cause difficulty with compliance. Patients should be warned that their stool will probably appear black when taking iron.
What are the indications for IV iron replacement therapy?
Most commonly used in patients with either CKD or the anaemia of malignancy in conjunction with treatment with erythropoiesis stimulating agents. Treatment with ESAs may result in a functional iron deficiency and this can be overcome by IV but not oral iron.
IV iron is also indicated in iron deficient patients who are genuinely intolerance of oral iron or who are unable to absorb it adequately.
