Transcutaneous Auricular Vagus Nerve Stimulation for Preventing Acute Kidney Injury in Patients Undergoing Cardiac Surgery With Cardiopulmonary Bypass

Acute kidney injury (AKI) is a common complication after cardiac surgery using cardiopulmonary bypass, leading to longer hospital stays and worse outcomes. Effective preventive therapies are lacking. This randomized controlled trial investigates whether transcutaneous auricular vagus nerve stimulation (taVNS)-a non-invasive ear stimulation technique-can reduce AKI after cardiac surgery. A total of 152 patients undergoing elective cardiac surgery with cardiopulmonary bypass will be randomly assigned to receive either taVNS or sham stimulation. The intervention begins before surgery and continues daily through postoperative day 5. The primary outcome is the incidence of AKI within 7 days after surgery. Secondary outcomes include AKI severity, need for dialysis, kidney function recovery, complications, and inflammatory biomarkers. This study is approved by the institutional ethics committee. All participants will provide written informed consent.

Inclusion Criteria: * Age ≥18 years * Scheduled for elective cardiac surgery with cardiopulmonary bypass under general anesthesia * Baseline estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m² (CKD-EPI formula) * American Society of Anesthesiologists (ASA) physical status classification I-III * New York Heart Association (NYHA) functional classification I-III * Able to understand and cooperate with study procedures * Willing to participate and provide written informed consent. For participants unable to read or sign due to incapacity or illiteracy, consent may be obtained from a legally authorized representative or witnessed by an impartial third party as per ethical guidelines Exclusion Criteria: * Solitary kidney, history of kidney transplantation, pre-existing renal replacement therapy, or pre-existing acute kidney injury (KDIGO criteria) * Contraindications to transcutaneous auricular vagus nerve stimulation, including active infection, dermatitis, skin breakdown, or severe psoriasis in the bilateral auricular region; allergy to silicone, electrode gel, or device materials; uncontrolled arrhythmia, symptomatic bradycardia, sick sinus syndrome, second- or third-degree atrioventricular block, implanted pacemaker or defibrillator; carotid sinus hypersensitivity; uncontrolled epilepsy; or active peptic ulcer disease * Received vagus nerve stimulation, auricular acupuncture, or transcutaneous electrical nerve stimulation within 1 month prior to enrollment * Long-term use of medications that significantly affect autonomic nervous system tone or renal blood flow and cannot be safely paused before surgery * Active systemic infection or sepsis (Sepsis-3 criteria) prior to surgery * Acute ischemic or hemorrhagic stroke, or acute myocardial infarction within 3 months prior to enrollment * Severe hepatic dysfunction (Child-Pugh Class C), acute liver failure, or other serious life-threatening conditions * Vulnerable populations (excluding elderly or illiterate individuals) including critically ill patients, individuals with psychiatric disorders, cognitive impairment, or pregnant women * Any other condition deemed by the investigator to make the participant unsuitable for study participation