Anticoagulation and related emergencies

Question 1

What are the main indications for anticoagulation?

Answer 1

=> Therapeutic:
- Venous thromboembolic disease: DVT and PE

=> Prophylactic:

• Prevention of DVT/PE in high risk patients
• Prevention of stroke (eg in chronic AF)

Question 2

What are the 2 different kind of Heparin?

Answer 2

=> Low Molecular Weight Heparin (LMWH)
Eg. Dalteparin, Enoxaparin, Tinzaparin
- Preferred option in the initial treatment of VTE
- Inactivates factor Xa

=> Unfractionated Heparin (UFH)
- Binds to antithrombin

Question 3

What are the side effects and contraindication of Heparin?

Answer 3

=> Side effects:

• Increased risk of bleeding
• Heparin induced thrombocytopenia (HIT) - (despite being associated with thrombocytopenia, HIT is a pro-thrombotic condition)
• Osteoperosis
• Hyperkalaemia (through inhibition of aldosterone secretion)

=> Contraindications:

• Bleeding disorders
• Platelets
• Previous HIT
• Peptic ulcers
• Cerebral haemorrhage
• Severe hypertension
• Neurosurgery

Question 4

What is Warfarin?

Answer 4

Anti-coagulant which inhibits enzyme responsible for the regeneration of vitamin K

=> Patients on Warfarin are monitored using INR

Question 5

What is INR?

Answer 5

International Normalised Ratio is a way of quantifying how quickly a person can clot compared to the average person

INR = Patient Pro-thrombin time / Normal PT

Question 6

What are the indications for Warfarin use?

Answer 6

• Venous thromboembolism (Target INR = 2.5, 3.5 if recurrent)
• AF (Target INR = 2.5)
• Mechanical heart valves

Question 7

What factors potentiate Warfarin?

Answer 7

• Liver disease
• P450 enzymes inhibitors
• Cranberry juice
• Drugs which displace Warfarin eg. NSAIDs
• Drugs that inhibit platelet function

Question 8

What are the side effects of Warfarin?

Answer 8

• Haemorrhage
• Teratogenic
• Skin necrosis
• Purple toes

Question 9

What is the management of high INR with Warfarin?

Answer 9

=> Major bleeding:

• Stop warfarin
• Rapid IV Vitamin K infusion
• Give pro-thrombin complex

=> INR > 8.0, Minor bleeding:

• Stop Warfarin
• Give IV vitamin K
• Repeat IV vitamin K dose if INR still high after 24 hours
• Restart Warfarin when INR < 5.0

=> INR > 8.0, No bleeding:

• Stop Warfarin
• Oral vitamin K
• Repeat vitamin K dose if INR still too high
• Restart when INR < 5.0

=> INR 5.0-8.0, Minor bleeding:

• Stop Warfarin
• Give IV Vitamin K
• Restart Warfarin when INR < 5.0

=> INR 5.0-8.0, No bleeding:

• Withhold 1 or 2 doses of Warfarin
• Reduce subsequent maintenance dose