Patients in each of the three groups were routinely administered 10 mL/kg/h lactated Ringer's solution in an open hand vein upon admission, and the mean arterial pressure (MAP), electrocardiogram, pulse oxygen saturation (SpO2), and bispectral index (BIS) value (ConView YY‐106, Pearl Care) were continuously monitored with a multifunctional monitor. After the monitoring was completed, all patients underwent radial artery puncture and catheterization under local anesthesia to monitor the real‐time invasive arterial blood pressure, and efforts were made to relieve any nervousness. After lying down for 10 min, anesthesia was induced after the patient was quiet and the vital signs were stable. All patients underwent nitrogen removal and were given oxygen for 3 min (flow rate of 5 L/min), and 0.4 μg/kg sufentanil (Hubei, Yichang Humanwell Pharmaceutical Co., Ltd.) was administered by slow intravenous infusion. After 2 min, patients in group C1, group C2, and group C3 were slowly injected with 0.2, 0.3, and 0.4 mg/kg ciprofol (Liaoning HISCO Pharmaceutical Co., Ltd.), respectively, for 30 s. A dose of 0.2 mg/kg cis‐atracurium (Jiangsu Hengrui Pharmaceutical Co., Ltd.) was then administered. After all of the drugs had been injected after approximately 2–3 min, muscle relaxation was achieved and tracheal intubation was performed. Endotracheal intubation was required to be successful in one attempt. After successful intubation, mechanical ventilation was connected to the anesthesia machine, and respiratory parameters were adjusted. Continuous inhalation of 1.5% sevoflurane (Shanghai Hengrui Pharmaceutical Co., Ltd.) was administered to maintain anesthesia. During induction of anesthesia, if the BIS value continued to be greater than 60, 0.1 mg/kg ciprofol was administered each time for remedial sedation. The duration of administration was 10 s, and each additional interval was >1 min until the BIS value stabilized below 60.
The following evaluation time points were defined: T0: Admission (basal); T1: Before endotracheal intubation; T2: 10 s after endotracheal intubation; T3: 3 min after endotracheal intubation; T4: 5 min after endotracheal intubation.