title: Utility of anti-xa monitoring in children receiving enoxaparin for therapeutic anticoagulation.
abstract: Although enoxaparin is used to treat thromboembolism in children, current treatment guidelines are largely extrapolated from adults. The objectives of this study were to determine: i) correlation between enoxaparin dose and anti-factor Xa (anti-Xa) level, ii) intra-patient variability, and iii) whether dose or anti-Xa level is a predictor of outcomes. A retrospective chart review was conducted on all hospitalized patients receiving enoxaparin in a tertiary care pediatric institution. Simple linear regression, coefficient of variation (CV), and Student's t-test were used to analyze the objectives. Eighty treatment courses with interpretable anti-Xa levels were analyzed. Mean patient age was 6.5 years. Mean enoxaparin dose was 1.10 mg/kg q12h. Correlation between initial dosing and anti-Xa level was poor; R(2) = 0.0307 and 0.0237 for patients > 2 months with and without cardiac or renal diseases, respectively. Four out of seven patients ≤ 2 months of age compared to 4/32 patients > 2 months had a CV > 40%. Similarly, 4/12 cardiac patients compared to 4/27 non-cardiac patients had a CV > 40%. Neither dose nor anti-Xa level predicted treatment success or adverse reactions (P > .05). These results suggest a need to reexamine the use of anti-Xa levels for guiding enoxaparin therapy. Further prospective studies are warranted to clarify whether routine or selective anti-Xa monitoring should be recommended in pediatric patients.
authors.affiliation: Department of Pharmacy, St. Paul's Hospital, Providence Health Care, Vancouver, British Columbia, Canada.
authors.forename: Marianna
authors.initials: M
authors.lastname: Leung
authors.forename: Sharon H
authors.initials: SH
authors.lastname: Ho
authors.forename: Donald P
authors.initials: DP
authors.lastname: Hamilton
authors.forename: John K
authors.initials: JK
authors.lastname: Wu
authors.forename: David B
authors.initials: DB
authors.lastname: Dix
authors.forename: Louis D
authors.initials: LD
authors.lastname: Wadsworth
authors.forename: Mary H H
authors.initials: MH
authors.lastname: Ensom
keywords: Anti-factor Xa; enoxaparin; low molecular weight heparin