It is reported that over 50% of patients undergoing major abdominal surgery experience perioperative anxiety, which often triggers a vicious cycle of "anxiety-pain-gastrointestinal dysfunction" and significantly hinders postoperative recovery. Existing pharmacological and psychological interventions are limited by adverse effects such as respiratory depression, paralytic ileus, and poor patient compliance. While transcutaneous auricular vagus nerve stimulation (taVNS) has shown promise as a non-invasive neuromodulation technique for chronic neuropsychiatric disorders, high-quality evidence regarding its application in anxiety-susceptible perioperative populations is still lacking. This multicenter, randomized, parallel-group, double-blind, sham-controlled trial aims to recruit 282 patients undergoing elective major abdominal surgery across four centers in Mainland China. Eligible participants will be randomized (1:1) to receive either taVNS or sham stimulation for 60 minutes daily from two days prior to surgery through the day of the operation. The primary outcome is the incidence of perioperative anxiety from the day of surgery to 72 hours postoperatively, while secondary outcomes include depression, sleep quality, pain intensity, postoperative delirium, frailty scores, quality of recovery, time to first flatus and defecation, and length of hospital stay.

Inclusion Criteria:

1. Age: Between 18 and 85 years.
2. Patients undergoing elective major abdominal surgery under general anesthesia, with an anticipated operative duration of ≥ 2 hours and a predicted postoperative length of stay of ≥ 2 days.
3. ASA classification I-III.

Exclusion Criteria:

1. Active skin breakdown, erythema, swelling, infection of the ear, or significant anatomical abnormalities of the external ear.
2. Pre-existing bradycardia (resting heart rate < 50 beats/min) or third-degree atrioventricular block.
3. Presence of a cardiac pacemaker or other active electronic implants.
4. A documented history of traumatic brain injury within the past 6 months.
5. Chronic pain or long-term reliance on analgesic medications.
6. Severe neuropsychiatric disorders or chronic use of psychotropic medications, including corticosteroids, antidepressants, or anxiolytics.
7. Severe cognitive impairment or any condition precluding effective communication or completion of the assessment scales.
8. Women who were pregnant, lactating, or planning to conceive.
9. Current enrollment in other interventional clinical trials.
10. Anticipated direct transfer to the ICU immediately following surgery.