Efficacy of Sodium Heparin for Prophylaxis of Venous Thromboembolism in Surgical Patients

Inclusion Criteria: * Accept all items described in IC signing it in two ways; * Be aged between 18 and 60; * Be alert to the need for surgery antithrombotic prophylaxis; * Be classified as "moderate risk" for developing VTE, according to the protocol of prophylaxis of deep vein thrombosis of the Brazilian Society of Angiology and Vascular Surgery. Exclusion Criteria: * Acute coronary syndrome, it will make use of anticoagulation; * Immobilization of the lower limbs due to fractures, because in this way will be considered as high risk; * History of recent stroke; * Patients at high risk of bleeding in which the use of heparin is contra-indicated; * General Surgery in patients over 60 years in the case of patients at high risk for VTE; * general surgery in patients 40 to 60 years with additional risk factors for development of VTE; * Major amputations; * More orthopedic surgeries; * Patients with pre-surgical diagnosis of malignant neoplasms; * Patients with a platelet level below 100x109 / L; * Use of anticoagulants 48 hours before randomization; * Severe liver failure; * Be classified as "Low Risk" or "high risk" for developing VTE, according to Maffei et al. (2005); * Pregnancy and lactation.