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Heparin Resistance

Heparin Resistance. “Heparin resistance is a term used to describe the situation when patients require unusually high doses of heparin to achieve a therapeutic APTT” “ True resistance ” refers to a situation where the low APTT is reflective of a true absence of anticoagulation

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Heparin Resistance

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  1. Heparin Resistance • “Heparin resistance is a term used to describe the situation when patients require unusually high doses of heparin to achieve a therapeutic APTT” • “True resistance” refers to a situation where the low APTT is reflective of a true absence of anticoagulation • “Psuedoresistance” refers to a situation where the patient is adequately anticoagulated despite a low APTT • Has been arbitrarily defined as the requirement for >35,000 units/24 hours • ~25% of patients with VTE fulfill this requirement Chest 2001;119:64S-94S

  2. Heparin: Background

  3. Heparin: Mechanism Only heparin molecules with at least 18 saccharides (~6000 daltons)can bind both antithrombin and thrombin ATIII forms irreversible covalent bonds with thrombin or Xa Only activated coagulation factors are targeted Unique Pentasaccharide sequence that interacts with antithrombin

  4. AT III

  5. Heparin: Monitoring APTT http://www.fritsmafactor.com/newfritsmafactor/?p=2489

  6. Heparin Resistance: Mechanisms

  7. Heparin Resistance: Mechanism

  8. Heparin Resistance: Mechanism

  9. LMWH in patients with heparin resistance?

  10. Fondaparinux in patients with heparin resistance?

  11. Rivaroxaban in patients with heparin resistance?

  12. Dabigatran in patients with heparin resistance?

  13. Heparin Resistance Summary • Should be evaluated for when patients are receiving >35,000 units/24 hour period • Patients with heparin resistance may be over or under anticoagulated depending on the etiology of their resistance • If possible consider switching to alternative agent (LMWH, fondaparinux or oral anticoagulant) • If not possible consider testing anti-factor Xa levels (target 0.35 to 0.7 u/ml). If therapeutic with low aPTT then likely psuedoresistance

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