Presentation Details
| Transitioning from oral factor Xa inhibitor to unfractionated heparin using heparin-calibrated anti-Xa levels Mahnoor M Khan1, Magdalena E Jasinska2, Jeremy P Kosacz3, Erin N Robinson1, Lisa M Thompson3, Brandon Pierce3, Anne E Rose1. 1UW Health - Madison, Madison, WI, USA.2University of Wisconsin School of Pharmacy, Madison, WI, USA.3UW Health - Northern Illinois, Rockford, IL, USA |
Abstract
Background: Factor Xa inhibitors (FXAi) have become the most common choice for oral anticoagulation. However, FXAi can interfere with heparin-calibrated anti-Xa assays, making it challenging to titrate unfractionated heparin (UFH) infusions when anti-Xa levels are used. To account for this interference, some institutions choose to revert to monitoring UFH infusions with aPTT. Our health system uses an UFH titration nomogram targeting a higher anti-Xa goal (0.7-1.0 IU/mL) for patients with FXAi use in the previous 48 hours. Objective: The purpose of this study was to illustrate FXAi interference on baseline anti-Xa levels and evaluate the safety and efficacy of a higher anti-Xa goal for UFH titration with recent FXAi use. Methods: A retrospective chart review of UFH infusions started within 48 hours of FXAi use was conducted at two hospitals within the health system. Patients were excluded if they were <18 years old, had bleeding on admission, if UFH was not administered within 48 hours of last FXAi dose, if last FXAi dose was unknown, if UFH was administered at a fixed rate, if UFH targeted an alternative anti-Xa range, or if other concurrent anticoagulants were given. UFH infusions that met inclusion criteria were assessed to determine if the standard anti-Xa or the higher anti-Xa range were used. The standard range group (SRG) anti-Xa target is 0.3-0.7 IU/mL and the higher range group (HRG) anti-Xa target is 0.7-1.0 IU/mL. Baseline characteristics, anti-Xa levels, major bleeding events, thrombotic events, and non-clinically significant bleeding events were collected for both groups. The study was not powered to show statistical significance; data is reported as descriptive statistics. Results: One hundred and forty-three UFH infusions were included. Within these, 107 utilized the standard range and 36 utilized the higher range. The average time between last FXAi dose and the start of UFH infusion was 20.8 hours in the SRG and 18.8 hours in the HRG. The average baseline heparin anti-Xa level was 0.5 in the SRG and 0.9 in the HRG. In the SRG, the average anti-Xa levels within the first 24 hours after the UFH was started were 0.87, 0.72, 0.57, and 0.55 IU/mL. In the HRG the average anti-Xa levels within the first 24 hours after the UFH was started were 1.0, 0.86, 0.74, and 0.69 IU/mL. Two major bleeds occurred in the SRG and 1 major bleed in the HRG. One new thrombotic event occurred in the SRG and no thromboses reported in the HRG. There were 13 non-major bleeds in the SRG and 3 in the HRG. Conclusions: Utilizing an UFH titration nomogram targeting a higher anti-Xa goal for patients with FXAi use in the previous 48 hours may offer a potential solution for UFH titration when anti-Xa interference is present.
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