• Rachael T Overcash, Alicia T Somers, and D Yvette LaCoursiere.
• Division of Maternal-Fetal Medicine, Department of Reproductive Medicine, the Department of Pharmacy, and the Division of Obstetrics and Gynecology, Department of Reproductive Medicine, University of California San Diego, San Diego, California.
• Obstet Gynecol. 2015 Jun 1; 125 (6): 1371-6.

ObjectiveTo compare the adequacy of venous thromboembolism prophylaxis based on anti-Xa concentrations between weight-based enoxaparin dosing and body mass index (BMI)-stratified dosing in morbidly obese women after cesarean delivery.MethodsA prospective sequential cohort study of women with BMIs of 40 or greater who underwent cesarean delivery was conducted. Participants received either weight-based or BMI-stratified enoxaparin dosing to prevent venous thromboembolism formation. The weight-based regimen was 0.5 mg/kg of enoxaparin every 12 hours. In the BMI-stratified regimen, women with BMIs of 40-59.9 received 40 mg enoxaparin every 12 hours and women with BMIs of 60 or greater received 60 mg every 12 hours. The primary outcome was an anti-Xa concentration in the adequate thromboprophylaxis range (0.2-0.6 international units/mL). Secondary outcomes included enoxaparin dosage, timing of dosing and anti-Xa concentration, estimated surgical blood loss, postoperative changes in hemoglobin and platelets, wound hematoma, and adverse reactions to enoxaparin. Univariate analysis was used to compare dosing regimens.ResultsForty-two morbidly obese women received weight-based enoxaparin, and 43 received BMI-stratified dosing. Anti-Xa concentrations were significantly higher in the weight-based group compared with the BMI-stratified group (0.29±0.08 international units/mL compared with 0.17±0.07 international units/mL, P<.001). Thirty-six participants (86%) on weight-based dosing had anti-Xa concentrations within the prophylactic range compared with 11 (26%) on BMI-stratified dosing (P<.001). No participant had an anti-Xa concentration of 0.6 international units/mL or greater, the therapeutic threshold for venous thromboembolism prophylaxis.ConclusionIn morbidly obese women after cesarean delivery, weight-based dosing of enoxaparin for venous thromboembolism prophylaxis is significantly more effective than BMI-stratified dosing in achieving adequate anti-Xa concentrations.Level Of EvidenceII.

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