Enoxaparin and Antifactor Xa Levels in Pediatric Acute Burn Patients

Abstract

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.

Increased Enoxaparin Dosing Requirements for Treatment of Deep Vein Thrombosis in a Severely Burned Patient: Case Report and Literature Review

“…The lower than target activity of enoxaparin in this case mirrors previous literature in burn and trauma patients receiving prophylactic dosing of enoxaparin . The largest of these studies is a prospective observational study in which patients were followed throughout their stay and then received a 30‐day follow‐up telephone interview to determine whether VTE events had occurred .…”

“…The lower than target activity of enoxaparin in this case mirrors previous literature in burn and trauma patients receiving prophylactic dosing of enoxaparin. [4][5][6][7][8]13 The largest of these studies is a prospective observational study in which patients were followed throughout their stay and then received a 30-day follow-up telephone interview to determine whether VTE events had occurred. 6 The patients were given enoxaparin following an institution-specific prophylactic dosing protocol algorithm that recommended dose increases with anti-Xa monitoring.…”

“…4 Since then, several small studies have suggested this alteration of the usual pharmacokinetic profile in both burn and trauma patients, two notably similar groups of patients. [5][6][7][8][9] Lower than target anti-Xa activity observed in this population has been attributed to augmented clearance and increased volume of distribution. 10 To our knowledge, no evidence exists assessing the efficacy of enoxaparin dosing for treatment of VTE in the burn population.…”

“…A 2004 case series first evaluated enoxaparin dosing in burn patients, detailing lower than target anti‐Xa levels with standard prophylactic doses for deep‐vein thrombosis (DVT) prophylaxis . Since then, several small studies have suggested this alteration of the usual pharmacokinetic profile in both burn and trauma patients, two notably similar groups of patients . Lower than target anti‐Xa activity observed in this population has been attributed to augmented clearance and increased volume of distribution .…”

Hypercoagulability and Venous Thromboembolism in Burn Patients

“…Several studies have examined the relationship between burns, enoxaparin, VTE, and antifactor Xa levels. [47][48][49][50][51] It is well known that there are alterations in the pharmacokinetics of burn patients after thermal injury, related to both the initial capillary leak followed by enhanced renal and hepatic clearance. The current evidence suggests that standard dosing of enoxaparin may not be adequate in burn patients.…”