Anesthesia induction Upon each patient's arrival at the holding area, we placed an 18-gauge IV line in the right forearm vein and administered 10 mL/kg/hour of lactated Ringer's solution, 0.2 mg of glycopyrrolate, and 0.03 mg/kg of midazolam, as a premedication. Once in the operation room, we started to monitor electrocardiography, non-invasive BP, HR, pulse oximeter oxygen saturation, and the bispectral index (BIS). Anaesthesia induction was started in the following manner. Patients took a spontaneous respiration with inspired oxygen (8 L/min) through a transparent facemask and a circulation system with a reservoir bag. Bolus propofol (2.0 mg/kg) was administered intravenously for 10 seconds, after which assisted ventilation followed. After 5 minutes, complete induction was confirmed via a lack of train-of-four response and followed by tracheal intubation for maintenance anesthesia.