Heparin, warfarin, and direct oral anticoagulants with their antidotes, lab monitoring, and bleeding precaution teaching points.
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- What is the mechanism of action of heparin?
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It binds antithrombin III and potentiates its action, inactivating thrombin and factor Xa.- Which lab test is used to monitor unfractionated heparin therapy?
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aPTT (activated partial thromboplastin time).- What is the typical therapeutic aPTT range for a patient on unfractionated heparin?
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About 1.5 to 2.5 times the normal control value.- Heparin
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Protamine sulfate- By what routes is unfractionated heparin typically administered?
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IV infusion or subcutaneous injection, never IM.- What serious adverse reaction involves a drop in platelet count during heparin therapy?
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Heparin-induced thrombocytopenia (HIT).- Name a commonly used low molecular weight heparin (LMWH).
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Enoxaparin.- Does LMWH (enoxaparin) require routine aPTT monitoring like unfractionated heparin?
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No, it has a predictable dose response and is not routinely monitored.- What is the mechanism of action of warfarin?
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It inhibits synthesis of vitamin K-dependent clotting factors II, VII, IX, and X.- Which lab values are used to monitor warfarin therapy?
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PT (prothrombin time) and INR (international normalized ratio).- What is the typical therapeutic INR range for a patient on warfarin for standard indications?
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2.0 to 3.0.- Warfarin
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Vitamin K (phytonadione)- Besides vitamin K, what can be given for rapid reversal of severe warfarin-induced bleeding?
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Fresh frozen plasma or prothrombin complex concentrate.- Why is heparin often used as a bridge when starting warfarin therapy?
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Warfarin takes several days to reach a therapeutic effect, so heparin provides immediate anticoagulation.- Why should patients on warfarin keep their vitamin K intake consistent rather than avoid it entirely?
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Sudden changes in vitamin K intake alter warfarin's effectiveness and destabilize the INR.
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