Procedures
The patient was deprived of food and water for 8 h before the operation. After entering the operating room, select the patient's right forearm vein for injection. The patient swallowed 10 ml of dyclonine hydrochloride mucilage. They were given an ECG monitor, connected to the bispectral index of the EEG, and then inhaled oxygen through a nasal catheter. Fully supply oxygen and remove nitrogen for 3 min under spontaneous ventilation, and the oxygen flow rate is 4–6 L/min. Anesthesia induction: three groups of patients were given alfentanil 5 μg/kg (slow injection within 30 s) and 0.4 ± 0.1 mg/kg (slow injection within 90 s) of ciprofol [