Prophylactic Use of Sodium Enoxaparin for Venous Thromboembolism in High-Risk Abdominal Surgery

Inclusion Criteria: * Men and women aged above 18 years undergoing abdominal surgery with general high risk for developing venous thromboembolism; * Who have provided their consent by signing the consent form. Exclusion Criteria: * Clinical evidence of Venous thromboembolism (VTE) in the selection; * treatment requirement with anticoagulant Low Molecular Weight Heparin, Unfracted Heparin, oral anticoagulant * suspicion or history of coagulumpathia * Heparin, enoxaparin allergy or hypersensitiviy known to heparin, enoxaparin, but not restrict to thrombocytopenia and/or induce thombose by heparin ou enoxaparin (thrombocytopenia induce by heparin \[TIH\], thrombocytopenia associate with heparin \[TAH\] or thrombotic thrombocytopenia syndrome induce by heparin \[STTIH\] * Active bleeding that can be increased by enoxaparin. * Previous history of known intracranial hemorrhage * Artery-venous malformation or a suspicion or known cerebral aneurism * Spinal, Epidural ou lumbar puncture analgesia in the last 24 hours previous of the first dose of the administration of the enoxaparin. * erosive diseases of the digestive tract especially gastroduodenal * Uncontrolled hypertension (systolic blood pressure \[BP\]\> 180mmHg or diastolic BP\> 100 mm Hg) at randomization or clinical hypertensive urgency; * bacterial endocarditis * heart valve prosthesis * characterized by severe renal insufficiency creatinine clearance \<30 ml / min * Intra-arterial thrombolic therapy * Thrombolic therapy within 24 hours. * Low Molecular Weight Heparin or Unfraction Heparin treatment with prophylactic dose over 48 hours before surgery or oral anticoagulant within 5 days before surgery * disturbance of consciousness and coma * Less than 6 months of expectative time life * Chemical dependency * Patient with anesthetic risk ASA III or ASA IV * morbid obesity with Body Mass Index ≥ 40 * Chronic use of corticosteroids * History of allergy to Unfraction Heparin, Low molecular weight heparin or pork products. * History of severe allergic episode, systemic anaphylaxis, or major urticarial disease Steven-Johnson * Participation in another clinical study within 12 months prior to inclusion * Potentially fertile woman without β-HCG negative harvested until 48 hours before operation or not using acceptable contraception for participation in this study * Changes the security checks up to 48 h before randomization: * Hemoglobin \<10 mg / dL; * ALT or AST ≥ 2.5 times ULN; * Platelet count \<100.000/mL; * INR ≥ 1.5; * Any condition which in the opinion of the investigator, could lead to increased risk for the patient or who makes it inappropriate for this study.