Intervention
Before anesthesia induction, patients in the TEAS group received TEAS treatment for 30 min at bilateral Feishu (BL13, located under the spinous process of the third thoracic vertebrae approximately 5 cm apart), Zusanli (ST36, located 5 mm below and lateral to the anterior tubercle of the tibia), and Hegu (L14, between the first and second metacarpal bones on the dorsum of the hand, the midpoint of the radial side of the second metacarpal bone) with a stimulator (SDZ-II model, Suzhou Medical Appliances Co. Ltd, Suzhou, China), which continued until the end of the operation.These acupoints are based on traditional anatomical positions. Prior to each treatment, calibration was performed with the TEAS device. Electrode tabs were placed on the bilateral BL13, ST36, and L14. The TEAS was maintained at a frequency of 2/100 Hz using a dilatational wave throughout the procedure. The current intensity varied from 5 to 15 mA. Patients in the sham group were only connected to the electrodes without initiating electrical stimulation. All participants were blinded to the allocation. Both types of interventions were performed by a single investigator. The data were collected by another investigator who unaware of the distribution.