How should heparinization be monitored in patients who already have a prolonged aPTT from LA? How about warfarin?
In patients who are heparinized, heparin levels can be monitored directly to give an indication of anticoagulant effect by measuring the antifactor Xa level. Alternatively, thrombin time (which measures the clotting system distal to the effects of aPL abs) can be used as an indicator of heparinization. In a patient on warfarin, the PT/international normalized ratio (INR) is not usually affected by LA and can be used to monitor the adequacy of anticoagulation. Additionally, a chromogenic factor X level <20% of normal is evidence of adequate anticoagulation with warfarin.