Presentation Details
| Necessity of anti-Xa level monitoring for prophylactic enoxaparin in children and adolescents: A single institution experience Rene Gonzalez1, Abigail Davison1, 2, Sarah E.Sartain1, 2, Clay T.Cohen1, 2. 1Texas Children's Hospital, Houston, TX, USA.2Baylor College of Medicine, Houston, TX, USA |
Abstract
Background: Prophylactic anticoagulation with enoxaparin is often used in hospitalized children with increased risk of developing venous thromboembolism (VTE). At Texas Children’s Hospital, weight-based prophylactic enoxaparin is utilized with a goal anti-Xa monitoring range of 0.2-0.4 units/mL. It is unclear whether monitoring of prophylactic levels is required. Objectives: To assess the percentage of patients within goal anti-Xa level range on their initial evaluation following initiation of prophylactic enoxaparin. Methods: A retrospective analysis of the electronic medical record was performed to identify all patients 0-18 years of age admitted to Texas Children’s Hospital between May 2021 and March 2023 who received subcutaneous enoxaparin for VTE prophylaxis. Subjects included in this study were any patient who received a twice daily dosing strategy of prophylactic enoxaparin (0.5 mg/kg subcutaneous every 12 hours) and had at least one anti-Xa level for evaluation. Peak anti-Xa levels not obtained within the therapeutic window of 4-6 hours following dose administration were excluded. Exclusion criteria included any patient receiving: treatment dosing of enoxaparin, prophylactic dosing frequency other than twice a day, and prophylactic dosing as a therapeutic treatment strategy in the setting of thrombocytopenia. Additional data collected included patient demographics, rationale for VTE prophylaxis, the number of enoxaparin dosing adjustments required to achieve prophylactic levels of 0.2-0.4 units/mL, and any bleeding and thrombotic complications noted during hospitalization. This study was approved by the Baylor College of Medicine Institutional Review Board. Results: Prophylactic enoxaparin was administered to 138 patients. The most common reason for enoxaparin prophylaxis was critical illness in the setting of COVID or MIS-C, noted in 58.7% (n=81) of patients. Additional patient characteristics are outlined in Table 1. A prophylactic anti-Xa level was achieved on initial enoxaparin dosing in only 41.3% (n=57) of patients and was less common in younger patients; breakdown by age group for patients achieving goal anti-Xa level on initial dosing was: 32.3% (n=10) of patients <1 year, 39.4% (n=28) of patients 1-13 years, and 52.8% (n=19) of patients >13 years. Initial levels were more commonly found to be sub-therapeutic in patients <1 year (58%, n=18) vs patients 13 years and older (30.6%, n=11). Additional enoxaparin dosing and level outcomes are outlined in Table 2. The mean number of dose changes required to achieve a prophylactic anti-Xa level for patients <1 year was 3.3, for 1-13 years was 1.3, and for >13 years was 0.89. There were 5 (3.6%) minor bleeding events and 3 (2.2%) thrombotic events noted. Conclusions: Our study demonstrates that monitoring anti-Xa levels for children and adolescents on prophylactic enoxaparin is required to ensure that adequate anticoagulation is being achieved. This is especially true in infants and children under 13 years of age who often require multiple enoxaparin dose adjustments prior to reaching prophylactic range. Future prospective studies are needed to determine the optimal enoxaparin levels for prophylaxis of children based on age and underlying VTE risk factors.
No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.
No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.