Study methods
Using a random number table created by statisticians using SPSS statistical software, 181 patients were allocated into three groups: esketamine low (EL) group, esketamine high (EH) group, and normal saline (NS) group. All patients had routine fasting for 8 h and liquid fasting for 2 h before surgery. Penehyclidine hydrochloride 0.01 mg/kg was injected intramuscularly 30 min before anesthesia. After admission to the operating room, venous access was established, and noninvasive blood pressure (BP), electrocardiogram (ECG), and pulse oxygen saturation (SpO