2.2. Subjects and Setting
All patients were visited by an anesthesiologist the day before the surgery. Patients were kept fasting for at least 8 hours before surgery. Syringes were identical in appearance, and all of them were encoded, and the surgeon, staff, and anesthesiologist were unaware of the contents of the syringes. A standard pulse oximetry monitor, a noninvasive blood pressure (NIBP) measurement device, and an ECG (electrocardiogram) were connected in the operating room. After an 18 cm venous catheter was inserted, 10 ml/kg of ringer lactate was infused. Baseline heart rate (HR), blood pressure, and oxygen saturation were recorded.