Anticoagulation

Risk Classifications Schemes

  • Caprini Risk Assessment – estimates venous thromboembolism risk for non-orthopedic surgeries. Low risk use SCDs. Mod risk use meds or SCDs. High risk use meds+SCDs. If risk of bleeding, use SCDs only.
  • CHADS2 – estimates stroke risk in Afib patients. Easiest one to use. Recommends aspirin, anticoagulant, or both, depending on risk.
  • CHA2DS2-VASc – a more accurate version of the CHADS2
  • ATRIA – Another scoring system that estimates stroke risk in Afib.
  • HAS-BLED – estimates risk of bleeding in Afib patients when considering starting anticoagulants.

Anticoagulants

  • Warfarin – oral, cheap, effective, well-established, but narrow therapeutic range, need to check INR frequently, risks of bleeding, warfarin necrosis, purple toe syndrome.
  • Apixaban (Eliquis) – less stroke/embolism, less major bleeding, less hemorrhagic stroke risk, less death from all causes, when compared with warfarin. Category B. $$$$
  • Dabigatran (Pradaxa) – less stroke/embolism, but equal major bleeding risk (less intracranial bleeding, more GI bleeding) when compared with warfarin. Category C. Not recommended for those >75. Dispense and store in original bottle, not pill organizer. $$$$
  • Rivaroxaban (Xarelto) – equal stroke/embolism, equal major bleeding risk (but less intracranial bleeding, more GI bleeding) when compared with warfarin. Category C. Needs to be taken with food. $$$$
  • Apixaban>Dabigatran>Rivaroxaban
  • Unfractionated Heparin (UFH) – IV, SC, fast acting
  • Low Molecular Weight Heparin (LMWH) – IV

Conditions

  • Atrial Fibrillation – INR range 2-3. Can start warfarin without need for bridge, if pt is low risk for thromboembolism. Can also use one of the new anticoagulants (Apixaban, Dabigatran, Rivaroxaban).
  • VTE prophylaxis post-surgery – LMWH (preferred), Fondaparinux, one of the new anticoagulants, low-dose UFH, warfarin, ASA, or SCDs x10-35d, or until fully ambulatory.
  • VTE prophylaxis non-surgical – LMWH, low-dose UFH, Fondaparinux if pt is immobilized/hospitalized. If at high risk of bleeding, use SCDs only. If low thrombotic risk, no prophylaxis recommended.
  • ACS – IV UFH x48h or until PCI, or enoxaparin throughout hospital stay.
  • Bioprosthetic Heart Valve Replacement – Use ASA for aortic valve replacements. Use Warfarin for Mitral valve replacements with INR goal >2.5
  • Mechanical Heart Valve Replacement – Use Warfarin/Bridge (UFH or LMWH). Target INR 2.5 for mechanical aortic valve, 3.0 for mechanical mitral or double valve.
  • VTE (DVT/PE) – Warfarin+bridge (x5days and until INR 2-3, bridge with IV/SC UFH or LMWH, which is preferred), or Rivaroxaban, or Dabigatran. Apixaban can also be used but it is not yet FDA approved for DVT treatment. If first time, treat 3 months. If recurrent, treat indefinitely.
  • Thrombophilia – test for Protein C deficiency, Protein S deficiency, Antithrombin III deficiency, Factor V Leiden, Prothrombin 20210A gene mutation, antiphospholipid antibodies.

Monitoring

  • Check baseline INR before beginning warfarin. Start Warfarin with 10mg x2 days to achieve therapeutic INR faster. Use 5mg for elderly. Check INR after 2-3 doses of warfarin, then 2x/wk, then qweek, then qoweek, then qmonth.
  • Pt taking same warfarin dose x3 months = stable. If pt has previously stable INR have single INR that is 0.5 less or above goal, wait 2 consecutive INR out of range before adjusting dose. Routine heparin bridging not needed for previously stable pts with single subtherapeutic INR.

Managing Adverse Effects

  • 4-factor prothrombin complex concentration (PCC) – Has factors 2,7,9, 10. Preferred over FFP for major bleeding from warfarin. If unavailable, can use 3-factor PCC (has 2, 9, 10). Can also add Vitamin K if pt has major bleeding.
  • Vitamin K – do not give if pt is not actively bleeding, unless INR>10.
  • Reversal agents for the new anticoagulants are currently being developed.
  • Warfarin Necrosis – skin necrosis, limb gangrene after 3-8 days of warfarin.
  • Purple Toe Syndrome – painful, purple lesions on toes or sides of feet, from cholesterol emboli. Happens 3-8 wks after starting warfarin. Discontinue warfarin.
  • HIT – results in thromboembolism. Happens 5-10d after starting heparin. Discontinue heparin, and put on Argatroban (direct thrombin inhibitor) instead.

Perioperative Management

  • Warfarin – Stop 5 days before surgery. If high risk of thrombus, bridge with heparin or LMWH while off warfarin prior to surgery. Stop 2-3d before dental procedure. No need to stop for minor derm procedure or cataract procedure.
  • Apixaban – Stop 24h before low bleeding risk procedures. Stop 48h before high bleeding risk procedures.
  • Dabigatran – Stop 1-2d for CrCl>50. Stop 3-5d for CrCl<50.
  • Rivaroxaban – Stop 24h before procedures.

 

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