RESUMO
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.
RESUMO
OBJECTIVE: To evaluate the ability of published dosage guidelines for enoxaparin to achieve therapeutic anticoagulation and to determine whether the routine monitoring of anti-Xa levels is still necessary at a tertiary care pediatric institution. METHODS: Consecutive charts and laboratory records were reviewed for all patients receiving treatment doses of enoxaparin for thrombosis in the authors institution over a 4-year period (1998-2002). RESULTS: Sixty-six percent (25/38) of the anti-Xa levels were within the recommended therapeutic range (0.5-1.0 [+/- 10%] U/mL) after two doses. The success rates of achieving therapeutic levels were 1/6, 2/3, 6/9, 10/11, and 6/9, for patients 2 months or younger, more than 2 months to 1 year, more than 1 year to 6 years, more than 6 years to 12 years, and more than 12 years of age, respectively. Patients with cardiac or renal disease were more likely to achieve high anti-Xa levels. Thirty-seven percent of patients reported adverse effects. The most common effects were injection site-related bruising and minor bleeding. One patient experienced a major bleed that was not life-threatening. CONCLUSIONS: Most patients achieved therapeutic anticoagulation when dosed according to the published guidelines. Children with cardiac conditions or renal insufficiency or those younger than 2 months were more likely to require dosage adjustments to achieve the therapeutic range. Routine monitoring of anti-Xa levels is still necessary in these patient populations, particularly when the early establishment of therapeutic anticoagulation may be critical. Enoxaparin appears to be well tolerated in the authors' patient population.
