(Cancer)

BNF: Patient on Anti-Coagulants:

BNF is only available in the UK

Overview

Anticoagulants → used for treating and preventing embolic events. The most common oral anticoagulants are vitamin K antagonists (warfarin) and DOACs (apixaban). The most common parenteral anticoagulant is Heparin.

• Vitamin K Antagonists (Warfarin)
  • Vitamin K → responsible for production of factors 2,7,9,10.
    • Has biggest affect on factor 7 → hence causes prolonged PT
  • Advantages → can be directly reversed by replacement of vitamin K
  • Disadvantages → long half-life, regular monitoring of PT and INR required, lots of interactions, not used in PE and DVT
    • INR ⇒ if INR raised significantly (indicates high bleeding risk), warfarin should be reduced or witheld completely and vitamin K may be given.
      • Target INRs (2.5 except mitral valve replacement) ⇒ AF (2.0-3.0), metallic aortic valve replacement (2.0-3.0), metallic mitral valve replacement (2.5-3.5), following VTE (2.0-3.0)
• DOACs
  • Apixaban and Rivoroxaban → factor 10a inhibitors
  • Now preferred to warfarin as they require less monitoring
• Heparin
  • Unfractionated (Standard) Heparin → IV, short acting, monitored via APTT
  • LMWH (eg. enoxaparin) → subcutaneous, long acting, monitored via anti-factor 10a. Usually preferred as lower risk of heparin-induced thrombocytopenia.
    • Activates antithrombin III. Forms a complex that inhibits factor 10a.
• Heparin vs Warfarin

Making Diagnosis

Assess bleeding risk (ORBIT score)

Management Plan

• Warfarin → stopped 5 days before planned surgery. Once persons INR is <1.5, surgery can go ahead (give oral vitamin K day before surgery if INR >1.5).

  • Heparin has much shorter half-life, so may be stopped on day of surgery (few hours before)

  Warfarin = avoid in pregnancy