Enoxaparin and Antifactor Xa Levels in Pediatric Acute Burn Patients

Previous work from the authors' group showed a risk for inadequate enoxaparin dosing for venous thromboembolism prophylaxis in adult burn patients when traditional recommendations are used. The purpose of this study was to determine whether this also applied to pediatric burn patients. Included patients were acutely burned, aged 14 years or under, and admitted to the authors' regional burn center between October 1, 2004 and December 15, 2012. Thirty-five patients included in this analysis received enoxaparin for venous thromboembolism prophylaxis dosed initially at 0.5 mg/kg and monitored with anti-factor Xa levels (anti-Xa) between 0.2 and 0.4U/ml. Of the included patients, 80% were male with a median age of 8 years, a median TBSA of 16%, and a median length of stay of 23 days. Initially 21 patients (60%) had an undetectable anti-Xa (<0.2 U/ml). Enoxaparin doses were increased but 18 patients (51%) never achieved target anti-Xa. There were no significant differences in sex, weight, dose, depth of injury, or body mass index between those who received appropriate prophylaxis and those who were undertreated. However, median size of burn was significantly larger, median age and height were significantly lower in those who did not reach target. The low number of patients achieving target prophylactic anti-Xa in this study demonstrates the need for routine anti-Xa monitoring in pediatric burns. Additionally, pediatric patients with major burn injury may require initial dosing of enoxaparin greater than published recommendations because of altered pharmacokinetics.