Blood Clots Flashcards
Venous Thromboembolism
Venous Thromboembolism (VTE) includes Deep-vein thrombosis (DVT) + Pulmonary Embolism and occurs as a result of thrombus formation in a vein
- High risk patients of VTE include
- > 60 years old,
- limited mobility,
- obese,
- malignant disease,
- thrombophilic disorder
- history of VTE.
- Pregnanacy and postpartum period are also risk factors
- It is essential to look at the risk of bleeding vs VTE
Examples of VTE treatment
- Mechanical: Stockings
- Pharmacological:
- LMWH can be used for prophylaxis in general + orthopaedic surgery
- Unfractionated heparin can be used in patients with renal failure
- Oral anticoagulants: apixaban, dabigatran + rivaroxaban are indicated for prophylaxis in hip/knee replacement surgery.
Heparin
Heparin has a fast onset of action and a short duration of action compared to a LMWH
Used in patients with a high risk of bleeding as its effects can be reversed quicker… In the case of a haemorrhage, Protamine is given to reverse the effects of this drug (but only partially effective for LMWH)
Pregnant women can take Heparin for VTE as it does not cross the placenta. But LMWH are preferred due to their risk of osteoporosis and heparin-induced thrombocytopenia.
LMWH are given in preference to Heparin for the treatment of VTE due to reasons highlighted above. Examples include: Dalteparin + Enoxaparin.
The duration of action for LMWH is LONGER… hence a ONCE daily dosing regimen (convenience).
Side effects of heparin
thrombocytopenia (reduced platelet count), hypokalaemia and haemorrhage.
Warfarin uses and action
• Warfarin can be used for AF, DVT + PE. It antagonises the effect of Vitamin K (needed to produce clotting factors) and it usually takes at least 48-72 hours for the full effect to be seen. If a quicker effect is needed… heparin should be used.
- Counselling point: taking ONCE daily at the SAME TIME each day
INR ranges and monitoring
- 2.5 for AF, DVT and PE
- 3.0 for mechanical aortic valves and
- 3.5 for recurrent DVT or PE in patients currently receiving anticoagulation and with INR >2
• INR monitoring should be carried out daily or on alternate days at first, then gradually increased to longer durations up to 12 weeks apart.
• Any changes to the patient’s condition or lifestyle may derange the INR and indicate more frequent monitoring (e.g. decreased liver function, change of medication, diet, smoking or alcohol intake).
- Recent weight loss, acute illness, diarrhoea and vomiting may also upset INR levels.
ADR of warfarin
The main adverse effect of warfarin is haemorrhage (bleeding). If there is any sign of bleeding warfarin should be stopped immediately, and the patient should be started on vitamin K1.
If they are not bleeding, but their INR > 8
give vitamin K1 by mouth and withhold warfarin until INR <5
If they are not bleeding and their INR > 5
then withhold 1 or 2 doses of warfarin.
Elective surgery whilst on warfarin
- Usually warfarin is stopped 5 days prior to any elective (planned) surgery and is restarted almost immediately after the procedure. Patients stopping warfarin prior to surgery who are considered to have a higher risk of VTE may require interim therapy (‘bridging’) with a LMWH – this should be stopped 24 hours before surgery and resumed 48 hours after surgery.
- If emergency surgery is required, the patient will need vitamin K1 with prothrombin complex depending on the timescale
Anticoagulant and antiplatelet therapy
Ideally anticoagulant therapy (slows clotting) should not overlap with antiplatelet therapy (prevent clotting). The risk of bleeding with Aspirin + Warfarin is less than with Clopidogrel + Warfarin.
Warfarin in renal impairment
Warfarin can be used in Renal impairment: increased frequency of INR monitoring needed in severe impairment.
Avoid warfarin
- Avoid in pregnancy + avoid cranberry juice (increases anticoagulant effect). Avoid changing diet of liver, sprouts, broccoli and leafy green vegetables (rich in Vitamin K).
Enzyme inducers (Crap GP’s Shout BS)
Carbamazepine Rifampicin Alcohol Phenytoin Griseofulvin Phenobarbital Sulphonylurea’s St John’s Wort Barbiturates Smoking