OC 06.2 - Rapid Enoxaparin Adjustment for Childhood Thrombosis/Thromboprophylaxis (REACT)

Background: Enoxaparin is the anticoagulant of choice in many pediatric patients, both for thromboprophylaxis and thromboembolism treatment. Consensus guidelines on therapeutic enoxaparin in children suggest q12hourly dosing with target anti-Xa of 0.5-1.0U/mL drawn 4 hours post-second enoxaparin dose. However, initial enoxaparin dosing is often imperfect and, while a post-second dose anti-Xa may be suitable for routine situations, in children at high-thrombotic risk (e.g., pulmonary/systemic cardiac shunts ≤3.5mm, post-thrombolysis procedure) extended periods of sub-optimal anticoagulation should be avoided. As such, strategies to optimize enoxaparin dosing earlier would be of clinical benefit.

Aims: To assess the utility of a peak-post-first enoxaparin dose anti-Xa to guide subsequent enoxaparin dosing in children at high-thrombotic risk treated by the KidClot program at Stollery Children’s Hospital.

Methods: A retrospective review of all pediatric patients (Jan/2022-Jan/2024) deemed high-thrombotic risk who had peak-post-first enoxaparin dose anti-Xa utilized for subsequent enoxaparin dosing. Patients with bleeding disorders and/or significant renal impairment were excluded. Data on patient demographics, enoxaparin dosing (timing/dose), anti-Xa values, bleeding/thrombotic events were collected through chart review.

Results: Utilizing peak-post-first enoxaparin dose anti-Xa resulted in all patients achieving therapeutic anti-Xa within 24hours of commencing enoxaparin. Eleven patients (age: 2wk-16yr) analyzed to date showed, 3/11 patients achieved therapeutic anti-Xa post-first enoxaparin dose, while the remaining 8/11 had the enoxaparin dose increased and interval between doses decreased (range 6-10hours). Post-second enoxaparin dose, 10/11 patients achieved therapeutic anti-Xa, while the final patient required another enoxaparin dose increase after peak-post-second dose anti-Xa of 0.46U/mL and achieved a therapeutic peak-post-third enoxaparin dose anti-Xa. No patient had supratherapeutic anti-Xa values, including when repeated within 3-5 days to monitor for accumulation. There were no thrombotic or bleeding events within 7 days of commencing enoxaparin.

Conclusion(s): Utilizing peak-post-first enoxaparin dose anti-Xa in children at high-thrombotic risk may help achieve therapeutic anti-Xa sooner without increased bleeding. Further studies and evaluation are needed.