According to the 3D-CAM scale, evaluate the incidence of Postoperative Delirium within 5 days after surgery in elderly patients receiving taVNS.The results are expected to provide evidence of the safety and efficacy of perioperative prophylactic use of taVNS in the clinical application of improving postoperative brain health in elderly patients, as well as theoretical and practical basis for subsequent studies or clinical applications.

This study aims to conduct a prospective, randomized controlled clinical trial on the preventive use of taVNS to improve the incidence of Postoperative Delirium(POD) in elderly patients undergoing anesthesia surgery. The intervention group will receive "standard-stimulation parameters" of taVNS（25HZ，250μs）, while the control group will receive "low-stimulation parameters" of taVNS(1HZ,250μs). The main outcome measure of the study was the incidence of POD within 5 days after surgery. Secondary outcome measures include incidence of new mild and severe postoperative neurocognitive impairment during hospitalization and 90 days, all-cause mortality rate at 90 days, incidence of related adverse events, and length of stay.

Inclusion Criteria:

• Age≥65 years
• Expected operation time≥ 2 hours
• Postoperative hospital stay≥ 4 days
• Sign the informed consent form

Exclusion Criteria:

• Neurosurgery or cardiac surgery
• Emergency surgery within 6 hours of admission
• End-stage disease with an expected survival of < 3 months
• Preoperative severe cognitive dysfunction affected perioperative cognitive function assessment
• Severe sinus bradycardia, AVB of degree II and above, pacemaker placement