Background: Venous thromboembolism (VTE) is the most frequent 30-day complication in patients with morbid obesity undergoing bariatric surgery. Therefore, there is a need for optimized low molecular weight heparin (LMWH) thromboprophylaxis dosing strategies in order to avoid VTE-associated morbidity and mortality in this patient population.
Objective: The primary goal was to evaluate if a pre-specified enoxaparin dosing regimen in patients undergoing bariatric surgery reaches anti-factor Xa (aFXa) levels in the defined target range (0.2-0.4 U/ml). Second, we aimed to identify biometric and laboratory parameters that might influence the aFXa value.
Methods: A prospective database of 236 patients with obesity who received thromboprophylaxis with enoxaparin was established. These patients were divided into two weight-adjusted groups (group 1 < 150 kg, group 2 ≥ 150 kg). Enoxaparin was administered twice daily; dosing was determined by weight (group 1, 2 × 40 mg/day; group 2, 2 × 60 mg/day). In both groups, the peak aFXa serum level was evaluated 3 days after initiating the thromboprophylaxis.
Results: In group 1 (body mass index (BMI) 42.94 ± 6.84 kg/m2, weight of 121.7 ± 17.49 kg), seventy-one of the included 124 patients (57.25%) reached the aFXa target range of 0.2 to 0.4 U/m. In group 2 (BMI 63.21 ± 10.05 kg/m2, weight of 191.66 ± 33.37 kg), 68 of 112 (60.71%) patients scored prophylactic aFXa range. Multiple regression of the biometric and laboratory parameters showed significance for weight, waist-to-hip ratio, glomerular filtration rate (GFR), creatinine, and HbA1c exclusively in group 1. There was no case of VTE within 3 months after surgery and no case of severe perioperative bleeding in those patients who underwent surgery.
Conclusions: Measurement of the aFXa level helps to define the real prophylactic thromboprophylaxis status in patients with obesity, especially in those with a weight above 150 kg. In patients at risk, the measurement of aFXa should be considered in routine clinical practice.
Keywords: Anti-factor Xa; Bariatric surgery; Bleeding; Enoxaparin; Super-obesity; Thromboembolism; Thromboprophylaxis.