The aim of this study is to verify, through clinical examination and doppler, the non-inferiority of the drug test (heparin sodium 5.000UI/0.25 mL - HIPOLABOR) in relation to the drug compared (heparin sodium 5.000USP/mL - APP) in preventing the development of venous thromboembolism (VTE) in patients undergoing surgery for medium risk for the development of this pathology.

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.