Anesthesia management
All patients were anesthetized by the same anesthesiologist. After a patient entered the operating room, intravenous access was established and a multifunctional monitor was connected for electrocardiography (ECG) and noninvasive measurement of blood pressure (BP) as well as blood oxygen saturation (SpO2); then, a bispectral index (BIS) monitor (186 − 0106, Kehui Medical Equipment International Trading Co., LTD) was connected. After 30 min of TEAS intervention, general anesthesia was performed for endotracheal intubation; the induction drugs were midazolam 0.05 mg/kg, sufentanil 0.5 µg/kg, propofol 2 mg/kg, and rocuronium 0.6 mg/kg. After endotracheal intubation, mechanical ventilation parameters were adjusted as follows: tidal volume 6–8 ml/kg, respiratory rate 12–16 breaths/minute, inspiratory expiratory ratio 1:2, oxygen flow rate 2 L/min to maintain end-expiratory partial carbon dioxide (PPropofol (4–12 mg·kgAll patients were treated with patient-controlled intravenous analgesia (PCIA) after surgery. The PCIA configuration method was as follows: sufentanil 2 µg/kg + ondansetron 8 mg + 0.9% sodium chloride, configured to total 100 ml.