 There are some risks of pulmonary edema in patients undergoing pulmonary lobectomy with one lung ventilation. The overloading of fluid administration could be related to the development of pulmonary edema in patents after thoracic surgery. But fluid restriction may cause major organ hypoperfusion during the surgery. The purpose of this study is to evaluate the ability of stroke volume variation as an indicator for a fluid responsiveness in patient who receives pulmonary lobectomy via thoracotomy. 