Prescribing anticoagulants

• Duration of treatment:

  • Isolated calf DVT: typically six weeks
  • Provoked VTE (induced by factors like oral contraceptives or pregnancy): three months
  • Unprovoked VTE or PE: at least six months
  • Recurrent PE, DVT and AF: long term therapy
• MOA:

  UFH = enhances activity of antithrombin - inhibition of factors IIa (thrombin) and XA

  LMWH = Targets factor Xa

  Warfarin = vitamin K antagonists - inhibit synthesis of factors II, VII,IX and X. Inhibition of regulatory factors C and S.

  DOACs = competitively inhibit both free and clot bound factor Xa

  Dabigatran = reversibly inhibits free thrombin, fibrin-bound thrombin and thrombin-induced platelet aggregation
• DOACs are typically stopped at least 24 hours preoperatively in procedures with lower bleed risk and at least 48 hours preoperatively in procedures with higher bleed risk
• Warfarin may require cessation up to 5 days before surgery to allow for INR normalisation. Oral phytomenadione administration is considered if the INR is above 1.5 before surgery.

  Can be started the evening after surgery or the next day
• Patients high risk of thrombosis who need to stop their anticoagulation prior to surgery can receive bridging therapy with LMWH. Needs to be stopped 24 hours prior to surgery.