Effect of Transcutaneous Auricular Vagus Nerve Stimulation on Postoperative Delirium and Negative Emotions in Patients Undergoing Cardiac Surgery

Inclusion Criteria: * Aged 18 to 85 years. Scheduled for elective cardiac surgery (e.g., CABG, valve replacement/repair). NYHA cardiac function class I-III. Willing and able to provide informed consent. Expected surgery duration ≥ 2 hours. Exclusion Criteria: * Preoperative MMSE score \< 24; severe communication barriers. History of diagnosed delirium, dementia, Parkinson's disease, schizophrenia, bipolar disorder, major depressive disorder, or long-term use of psychotropic drugs. Skin lesions, infection, or deformity of bilateral ears; history of ear surgery or nerve injury; allergy to electrode materials. Severe arrhythmia; implanted electronic devices (e.g., pacemaker, ICD). Participation in another interventional trial within 3 months. Other conditions deemed unsuitable by investigators.