Routine monitoring such as electrocardiogram(ECG), heart rate(HR), saturation of pulse oxygen(SpO2) were monitored after patient arrived at the operation room. Selected the forearm vein to open venous access, infused sodium lactate Ringer's solution before anaesthesia. Then began to epidural anesthesia: The patients were at left side lying position, the L2,3 gap was chosen for puncture. After determined the success of puncture, inserted the epidural catheter into the head side, the length of the epidural space is 4cm. By intraductal injection of 2% lidocaine 3ml, signs of spinal anesthesia were excluded. Additional 0.75% ropivacaine 10 ~ 20ml was injected to control the level of pain disappear on thoracic4(T4) or thoracic6(T6) to satisfy the operation needs. After the level of anesthesia completed, Dex group: dexmedetomidine was continuously infused by 0.5 μg/kg in 10 min, followed with 0.5 μg/kg/hr continuous infusion until the closure of the abdominal. normal saline(NS)group: Pumped in the same volume of normal saline. In the operation, if the blood pressure was lower than 70% before anesthesia given ephedrine 10 ~ 15mg, and 0.5mg atropine was used when the heart rate was lower than 60 beats per minute. All operations were performed by the same group of maieutologists.