Enoxaparin thromboprophylaxis in gastric bypass patients: extended duration, dose stratification, and antifactor Xa activity.

BACKGROUND: Morbidly obese patients undergoing gastric bypass surgery are at risk for postoperative venous thromboembolism. Evidence-based recommendations regarding the dosing and duration of thromboprophylaxis are lacking for morbidly obese surgical patients. The aims of this study were to evaluate the safety and efficacy of an extended duration, body mass index (BMI)-stratified enoxaparin thromboprophylaxis regimen in patients undergoing Roux-en-Y gastric bypass and to determine the resultant antifactor Xa (AFXa) activity in morbidly obese surgical patients. METHODS: In this prospective open trial, 223 patients (75% female, mean BMI 50.4 kg/m2) undergoing Roux-en-Y gastric bypass were assigned to receive enoxaparin 40 mg (BMI 50 kg/m2), n = 99) every 12 hours during hospitalization and once daily for 10 days after discharge. The AFXa levels were monitored serially, and dose adjustments were made for results outside the target prophylactic range (.2-.4 IU/mL +/- 10%) after the third dose. The safety and efficacy outcomes were major bleeding and venous thromboembolism. RESULTS: Roux-en-Y gastric bypass was performed laparoscopically in 208 subjects (93%). The duration of surgery averaged 99.5 +/- 31 minutes, and the median length of hospitalization was 3 days. Target prophylactic AFXa concentration was achieved by 74% of patients after the third enoxaparin dose; none reached the full anticoagulation concentration. One patient developed nonfatal venous thromboembolism (.45%). Four patients required transfusion (1.79%). Bleeding was not associated with a high AFXa concentration. CONCLUSION: This BMI-stratified, extended enoxaparin dosing regimen provided well-tolerated, effective prophylaxis against venous thromboembolism in patients undergoing gastric bypass surgery.