Search

Background: Despite thromboprophylaxis, postoperative deep vein thrombosis and pulmonary embolism occur after bariatric surgery, perhaps because of failure to achieve optimal prophylactic levels in the obese population. Objectives: The aim of this study was to evaluate the adequacy of prophylactic dosing of enoxaparin in patients with severe obesity by performing an antifactor Xa (AFXa) assay. Setting: An academic medical center. Methods: In this observational study, all bariatric surgery cases at an academic center between December 2016 and April 2017 who empirically received prophylactic enoxaparin (adjusted by body mass index [BMI] threshold of 50 kg/m2) were studied. The AFXa was measured 3–5 hours after the second dose of enoxaparin. Results: A total of 105 patients were included; 85% were female with a median age of 47 years. In total, 16 patients (15.2%) had AFXa levels outside the prophylactic range: 4 (3.8%) cases were in the subprophylactic and 12 (11.4%) cases were in the supraprophylactic range. Seventy patients had a BMI <50 kg/m2 and empirically received enoxaparin 40 mg every 12 hours; AFXa was subprophylactic in 4 (5.7%) and supraprophylactic in 6 (8.6%) of these patients. Of the 35 patients with a BMI ≥50 who empirically received enoxaparin 60 mg q12h, no AFXa was subprophylactic and 6 (17.1%) were supraprophylactic. Five patients (4.8%) had major bleeding complications. One patient developed pulmonary embolism on postoperative day 35. Conclusion: BMI-based thromboprophylactic dosing of enoxaparin after bariatric surgery could be suboptimal in 15% of patients with obesity. Overdosing of prophylactic enoxaparin can occur more commonly than underdosing. AFXa testing can be a practical way to measure adequacy of pharmacologic thromboprophylaxis, especially in patients who are at higher risk for venous thromboembolism or bleeding.

Background: Warfarin dosing after bariatric surgery may be influenced by alterations in gastrointestinal pH, transit time, absorptive surface area, gut microbiota, food intake, and adipose tissue. Objectives: The aim of this study was to describe trends in warfarin dosing after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). Setting: Single academic center. Methods: All patients chronically on warfarin anticoagulation before RYGB or SG were retrospectively identified. Indications for anticoagulation, history of bleeding or thrombotic events, perioperative complications, and warfarin dosing were collected. Results: Fifty-three patients (RYGB n = 31, SG n = 22) on chronic warfarin therapy were identified (56.6% female, mean 54.4 ± 11.7 yr of age). Of this cohort, 34.0% had prior venous thromboembolic events, 43.4% had atrial fibrillation, and 5.7% had mechanical cardiac valves. Preoperatively, the average daily dose of warfarin was similar in the RYGB group (8.3 ± 4.1 mg) and SG group (6.9 ± 2.8 mg). One month after surgery, mean daily dose of warfarin was reduced 24.1% in the RYGB group (P<.001) and 23.2% in the SG group (P = .002). At 12 months postoperatively, the required daily warfarin dose compared with baseline remained statistically different (RYGB: 6.8 ± 3.8 mg; SG: 6.1 ± 2.0 mg). Conclusions: The warfarin dose is expected to be decreased by approximately 25% from preoperative levels after both RYGB and SG. Lower dose requirement within the first month after bariatric surgery is followed by a trend toward increased warfarin dose requirements, but remain less than baseline. Because dose requirements change constantly over time, frequent postoperative monitoring of the international normalized ratio is recommended.