 The aim of this study is to verify, through clinical examination and doppler, the non-inferiority of the drug test heparin sodium 5.000UI0.25 mL - HIPOLABOR in relation to the drug compared heparin sodium 5.000USPmL - APP in preventing the development of venous thromboembolism VTE in patients undergoing surgery for medium risk for the development of this pathology. 