No premedication was given. The temperature of the operating room was maintained at 22˚ C. Patients were positioned supine with 15° left lateral tilt achieved using a wedge under the right buttock. Electrocardiograph(ECG), pulse oxygen saturation (SpO2), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate (HR) were monitored by one anesthesiologist (S/5 Anesthesia Monitor, GE Healthcare, Helsinki, Finland). Peripheral vein catheterization on the right hand was then performed, but no prehydration was given. A fixed volume of 500 ml hydroxyethyl starch solution was infused at the rate of 0.2 ml•kg-1•min-1, then Lactated Ringer's solution was infused at the same rate to the end of surgery. Combined spinal-epidural anesthesia was administered with patients in the left lateral position at the L3-4 vertebral interspace. A 16-gauge Tuohy needle was placed in the epidural space using loss of resistance to saline, then a 25-gauge Whitacre spinal needle was inserted through the Tuohy needle until the dura mater was punctured. Once free flow of clear cerebrospinal fluid (CSF) was observed in the spinal needle, 10 mg (2 mL) of isobaric bupivacaine 0.5% was diluted with CSF to 2.5 mL, then injected over 15-30 s. After placement and fixation of an epidural catheter, the patients were positioned supine with 15° left lateral tilt, and oxygen was given via nasal catheter at 2L.min-1. The sensory block level to cold was monitored every three minutes (1, 4, 7 and 10 min) with alcohol swabs and was recorded at the time point of 10 min. Hypotension was defined as SBP lower than 80% of the baseline value, and was treated with intravenous phenylephrine 100 µg as required. Intravenous atropine 0.3 mg was given for severe sinus bradycardia (HR < 50 beats/min). Surgery was allowed to start after the sensory block reached the T6 level; if this level was not achieved, patients were excluded from the study. For patients with inadequate sensory block, 1.5% lidocaine was given through the epidural catheter.