Morbid obesity, is known to be associated with a high risk of VTE and, unfortunately, fixed doses of anticoagulant regimens may not provide optimal VTE prophylaxis in these patients especially after surgery.

Venous thromboembolism (VTE) is serious and preventable in patients who have undergone recent surgery . Most surgical patients are required to receive VTE prophylaxis, usually pharmacologic prophylaxis. Notwithstanding, rates of appropriate perioperative thromboprophylaxis remain tenaciously low, although the expansion of quality-improvement efforts has led to widespread hospital implementation of prophylaxis strategies.

Obesity, including morbid obesity, is known to be associated with a high risk of VTE and, unfortunately, fixed doses of anticoagulant regimens (unfractionated heparins, low-molecular-weight heparins, and factor Xa inhibitors) may not provide optimal VTE prophylaxis in these patients especially after surgery. Cumulative evidence and works of the literature suggest that anticoagulant dose adjustments in morbidly obese patients may reduce VTE risk. With the increasing rate of morbid obesity, more high-quality clinical trials are needed to prevent VTE in morbidly obese surgical patients providing effective, safe, prevention strategies.

Rationale for Change: Due to challenges in recruiting orthopedic surgical patients within the study timeframe, the protocol has been amended to exclude this patient population. This change ensures the study can proceed with a feasible sample size while maintaining the integrity of the research question regarding LMWH thromboprophylaxis in non-orthopedic surgical patients with morbid obesity. This amendment will not alter the primary research question regarding the efficacy and safety of two doses of LMWH thromboprophylaxis. However, it will narrow the scope of the study to focus exclusively on non-orthopedic surgical patients

Inclusion Criteria:

1. Participants required surgical intervention in: general surgery, gynecology, bariatric surgery
2. Moderate, high, and very high risk for venous thromboembolism according to Caprin RAM
3. Participant is willing and able to give informed consent for participation in the study.
4. BMI ≥40kg/m2

Exclusion Criteria:

1. Having any contraindication to LMWH, such as active bleeding, history of heparin-induced thrombocytopenia , baseline platelet count <75 × 108/μl, severe renal disease (glomerular filtration rate <30 ml/minute), severe liver disease, or uncontrolled hypertension (>200/120 mmHg)
2. Known hypersensitivity to unfractionated or LMWHs
3. On oral or parenteral anticoagulants within 5 days before surgery
4. Severe arterial hypertension
5. Unable to comply with the study treatment and/or follow-up
6. Receiving prohibited medications
7. Pregnancy or lactation mother

outcome-assessor blinded study. Due to inherent color differences between the two types of LMWH, the treatment administration could not be fully masked. However, treatment allocation was masked from the outcome assessor from the start by using coded envelopes