The main aim of this study is to compare the influence of total body-weight (TBW), lean body-weight (LBW), ideal body-weight (IBW) or Body Mass Index (BMI) on peak anti-Xa levels at steady-state in bariatric surgery (BS) morbidly obese patients receiving a fixed double dose of dalteparin (5000 IU subcutaneously, twice daily a day) for venous thromboembolism (VTE) prevention. Secondary aims of this study are to identify which body size descriptors (BSD) has the greatest impact and could further be explored for an adjusted low molecular weight heparin (LMWH) dosing algorithm for achieving optimal VTE prevention in BS severely obese patients.

Severely obese patients undergoing bariatric surgery (BS) are at increased risk for venous thromboembolism (VTE). How standard LMWH regimen should be adapted to provide both sufficient efficacy and safety in this setting is unclear. The aim of this study is to compare the influence of four BSD on peak anti-Xa levels in BS obese patients receiving high LMWH fixed doses to identify which one had the greatest impact and could further be proposed in LMWH-based thromboprophylaxis dosing algorithms.

Inclusion Criteria:

• between 18 and 70 years old
• BMI ≥ 40 Kg/m² or BMI ≥ 35 Kg/m² with at least one or more obesity-related co-morbidities ( including type II diabetes (T2DM), hypertension, obstructive sleep apnea (OSA), non-alcoholic fatty liver disease, severe osteoarthritis, lipid abnormalities, gastrointestinal disorders, or heart disease)
• scheduled for sleeve gastrectomy (SG) or gastric bypass procedure (GBP)
• informed consent

Exclusion Criteria:

• anticoagulant administration within 48 hours preceding surgery
• on-going antiplatelet therapy
• pregnancy

Obese patients undergoing bariatric surgery