Anticoagulation

Definition | Indications | Mechanism of Action | Risk Factors | Monitoring and Side Effects | Investigations | Management

Definition

Anticoagulation refers to the use of medications to reduce blood clot formation and prevent thromboembolic events, commonly used in conditions such as atrial fibrillation, venous thromboembolism (VTE), and mechanical heart valves.

Indications

  • Atrial fibrillation: stroke prevention.
  • Venous thromboembolism (VTE): treatment and prevention of deep vein thrombosis (DVT) and pulmonary embolism (PE).
  • Prosthetic heart valves: prevention of valve thrombosis.
  • Thrombophilic disorders: prevention in high-risk individuals.
  • Peripheral arterial disease: secondary prevention of vascular events.

Mechanism of Action

  • Vitamin K antagonists (VKAs): warfarin inhibits vitamin K-dependent clotting factors (II, VII, IX, X).
  • Direct oral anticoagulants (DOACs): apixaban, rivaroxaban (factor Xa inhibitors); dabigatran (direct thrombin inhibitor).
  • Heparins: unfractionated heparin (UFH) and low molecular weight heparin (LMWH) enhance antithrombin activity.

Risk Factors

  • History of bleeding disorders.
  • Renal or hepatic impairment.
  • Concurrent use of antiplatelets or NSAIDs.
  • Recent surgery or trauma.

Monitoring and Side Effects

  • Warfarin: requires INR monitoring (target INR 2-3 for most indications).
  • DOACs: no routine monitoring needed but requires renal function assessment.
  • Bleeding risk: gastrointestinal, intracranial haemorrhage.
  • Heparin-induced thrombocytopenia (HIT) with UFH.

Investigations

  • Baseline clotting profile: PT, APTT, INR.
  • Renal and hepatic function: essential for DOAC dosing.
  • FBC: to assess for anaemia or thrombocytopenia.

Management

1. Initiation:

  • Warfarin: requires bridging with LMWH in high-risk cases.
  • DOACs: preferred for most VTE and AF patients due to ease of use.

2. Reversal of Anticoagulation:

  • Warfarin: vitamin K, prothrombin complex concentrate (PCC) for severe bleeding.
  • DOACs: such as epixaban/rivaroxaban or dabigatran.

3. Referral:

  • Haematology: for anticoagulation in complex cases (e.g., thrombophilia, HIT).
  • Cardiology: for anticoagulation in atrial fibrillation or mechanical valves.
  • Emergency care: for major bleeding or overdose requiring urgent reversal.
HaematologymypanotesAnticoagulation