Sedation protocol
The patients were fasted routinely for overnight, and received 5ml of oral 2% lidocaine hydrochloride mucilage and topical spray oropharyngeal anesthesia with 4% lidocaine as premedication 20 min prior to the start of the sedation. Then the patients were placed in prone position with their head on the right side and administered intravenous isotonic saline solution at a rate of 6–8 ml/kg/h throughout the procedure via a 20-gauge intravenous catheter that was inserted in peripheral veins of the left upper limb and connected via extension tubes to an infusion pump (BeneFusion SP5 Ex, Mindray Bio-Medical Electronics Ltd., Nanshan, Shenzhen, China) for propofol infusions. The patients were monitored according to our hospital standards including continuous monitoring of heart rate (HR), peripheral blood oxygen saturation (SpO2), end-tidal carbon dioxide (EtCO2), and mean arterial pressure (MAP) measured every 5 min. Supplemental oxygen was administered via a nasal cannula at 4 L/min throughout the procedure.Prior to the beginning of the sedation, all patients were intravenously administered 0.1 µg/kg sufentanil and then divided into two groups: group M and group N. In group M, 40 mg/kg magnesium sulfate diluted with normal saline to a total volume of 100 ml was administered for 15 min. The rationale for the dosage of the magnesium sulfate regimen was based on previous studies [At the end of the procedure, all infusion drugs were stopped immediately, and the dose of the agents were recorded. After the procedure, patients were transferred to the post-anesthesia care unit (PACU) for monitoring. The modified Aldrete Score was used to assess overall recovery of patients. Patients were allowed to be transferred to wards when a score of 9 or more was identified.