Haematological Medications Flashcards
How would you monitor unfractionated heparin levels?
APTT
How would you monitor LMWH?
Anti-Xa assay
How would you monitor warfarin activity?
INR
What is the mechanism of action of low molecular weight heparin?
Inactivates factor Xa (but not thrombin)
Why has LMWH replaced unfractionated heparin?
It is more predictable and has a longer half life
What is the mechanism of action of unfractionated heparin?
Inhibits thrombin, factor Xa and IXa
What are side effects of heparins?
- Bleeding
- Heparin induced thrombocytopenia
- Osteoporosis - long term
- Hyperkalaemia - due to aldosterone secretion
What are contraindicaitons for heparin use?
- Bleeding disorders
- Platelets < 60x109/L
- Previous HIT
- Peptic ulcer
- Cerebral haemorrhage
- Severe hypertension
- Neurosurgery
What is the mechanism of action of Warfarin?
Inhibits vitamin K-dependent γ-carboxylation of coagulation factors II, VII, IX and X, thus leading to biologically inactive forms. Also inhibits Protein C initially, creating a pro-thrombitic effect
Why is LMWH given with warfarin when beginning therapeutic anticoagulation?
Warfarin is initially pro-thrombotic due to inhibition of protein C
What are the side effects of warfarin?
- Skin necrosis - patients with protein C or protein S deficiency
- Haemorrhage
What are contraindications to warfarin use?
- Abnormalities of haemostasis
- Hypersensitivity to warfarin
- After an ischaemic stroke for 2–14 days
- Surgery
- Severe uncontrolled hypertension.
- Active peptic ulceration.
- Severe liver disease.
- Pregnancy
How would you manage someone with warfarin overdose and there is major bleeding?
- Stop warfarin
- Prothrombin complex concentrate 30–50 units/kg or FFP (15 mL/kg).
- Give vitamin phytomenadione (vitamin K1) 5 mg - Slow IV
If someone had an INR of >8 and was on warfarin, how would you manage them?
If no bleeding
- Stop warfarin
- 0.5-2.5mg Vitamin K - if risk factors for bleeding
- Check INR Daily
If someone had an INR of 6-8 and was on warfarin therapy, how would you manage them?
Stop warfarin, then restart when INR < 5