Postoperative acute pain control in patients with gastrointestinal tumors is not satisfactory, and surgical complications including gastrointestinal dysfunction, gastrointestinal fistula, abdominal and gastrointestinal hemorrhage, peritonitis and abscess, are still important factors affecting surgical outcomes, postoperative recovery, hospital stay, and even perioperative mortality. The application of taVNS during the perioperative period can enhance or preserve vagal nerve function, which may protect important organ functions through multiple pathways such as alleviating pain and inflammatory responses caused by surgical trauma, improving gastrointestinal function, enhancing cardiovascular regulation, reducing postoperative nausea and vomiting, and accelerating postoperative recovery, thereby reducing postoperative complications and mortality.

Subjects who met the inclusion criteria were enrolled in the clinical trial and received 2 interventions at the following times: the day before surgery, and the afternoon of the 1st day postoperatively (15:00-17:00), a total of 2 times. The intervention implementers used vagus nerve stimulation equipment to place electrodes in the tragus area of the outer ear of the subjects in the experimental group (taVNS group). The control group (sham stimulation group) was set to have a pulse width of 200 μs, a frequency of 1 Hz, and an initial current of 10 mA, which was gradually increased to the pain tolerance threshold of the subject, capped at 50 mA，last for one hour. The VAS scores before and after stimulation for 10 minutes were recorded.

2) ECG monitoring: Both groups were monitored with a dynamic ECG monitor during the intervention period, starting 10 minutes before stimulation and ending 10 minutes after stimulation. The SDNN (Standard Deviation of NN intervals) of the sinus rhythm was measured before and after stimulation for 10 minutes. A uniform standard was used for anesthesia induction and maintenance during surgery, and all patients used the same patient-controlled intravenous analgesia (PCIA) plan.

Inclusion Criteria:

Age 18-80 years, BMI 18-30 kg/m², ASA Ⅱ-Ⅲ, elective laparoscopic gastric or intestinal tumor surgery, expected surgical duration ≥2 hours, patient understands study content and signs informed consent form.

Exclusion Criteria:

Kidney replacement therapy, treatment for arrhythmias requiring treatment, dementia, severe bradycardia, orthostatic tachycardia syndrome, neuro-muscular disorders, auricular dermatitis, planned post-operative transfer to ICU