Brief Summary This study is designed to find out whether transcutaneous auricular vagus nerve stimulation (taVNS) can safely reduce restlessness and confusion when children wake up from anesthesia after tonsillectomy and adenoidectomy. These problems, called emergence agitation and delirium, are common after surgery and can cause distress for both children and their families.TaVNS is a non-invasive treatment that delivers mild electrical stimulation to a specific area of the ear connected to the vagus nerve. It does not involve needles or medication, and children usually feel only a gentle tingling sensation.In this randomized, double-blind study, children will be assigned by chance to receive either taVNS or a sham (placebo) stimulation during surgery. Neither the children, their families, nor the medical team providing care will know which treatment each child receives.Researchers will observe and record how calmly children wake up from anesthesia, whether they show signs of delirium, and any side effects. The goal of this study is to test whether taVNS is an effective and safe way to improve recovery and comfort for children after surgery.

Background and Rationale Emergence delirium (ED) in pediatric patients is a common postoperative complication linked to exposure to volatile anesthetics, particularly sevoflurane. The proposed mechanism involves dysregulation of the autonomic nervous system, characterized by reduced vagal tone and sympathetic hyperactivity. Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive neuromodulation technique designed to increase vagal activity by delivering low-intensity electrical currents to the auricular branch of the vagus nerve in the ear. Preclinical and clinical evidence suggests taVNS can exert anti-inflammatory, analgesic, and anxiolytic effects via central and peripheral pathways. This trial is designed to investigate whether perioperative taVNS can mitigate ED by modulating autonomic balance.

Intervention and Blinding Methodology The study employs a double-blind, sham-controlled design. Active and sham stimulation devices are physically identical. The active device delivers electrical stimulation with parameters set at a frequency of 25 Hz, a pulse width of 300 μs, and a cyclic mode of 30 seconds on followed by 30 seconds off. Stimulation intensity is individually titrated to a perceptible but non-painful tingling sensation. The sham device follows an identical placement and titration procedure but ceases output after the initial adjustment phase. This methodology ensures participants, caregivers, and outcome assessors are blinded to group assignment. Stimulation is initiated in the preoperative holding area, continues intraoperatively, and concludes upon discharge from the post-anesthesia care unit (PACU). Supplemental stimulation sessions are administered on postoperative days 1 and 2.

Study Procedures Overview Following enrollment and randomization, the stimulation device is applied to the left auricular concha. Standardized general anesthesia is administered per protocol, utilizing sevoflurane for maintenance with titration guided by bispectral index (BIS) monitoring. Intraoperative vital signs and anesthetic depth are recorded. Upon cessation of anesthetics, continuous behavioral observation begins in the PACU.

Technical and Mechanistic Considerations The selection of the left auricle for stimulation is based on anatomical studies indicating a lower density of cardiac vagal fibers compared to the right side. The chosen stimulation parameters (25 Hz, 300 μs) are derived from prior neurophysiology studies suggesting efficacy in activating afferent vagal pathways. The cyclic on/off pattern is intended to prevent nerve accommodation. The perioperative timing of stimulation is designed to preemptively modulate autonomic tone prior to the emergence phase, a period of high neurophysiological lability.

Data Collection and Management Primary and secondary outcome data are collected at predetermined time points by trained, blinded assessors. Data pertaining to device adherence (session timing, wear status) are recorded by nursing staff. All data are entered into a secure, electronic data capture system. Source data verification is performed per the monitoring plan.

Statistical Considerations The primary analysis will utilize the intention-to-treat principle. The primary endpoint, incidence of emergence delirium, will be compared between groups using a chi-square test. A secondary logistic regression analysis will adjust for predefined covariates (e.g., age, surgery duration) to evaluate the independent effect of the intervention. Analysis of continuous secondary endpoints will employ t-tests or non-parametric equivalents based on data distribution. A two-sided p-value <0.05 will define statistical significance.

Safety Monitoring Adverse events are monitored from device application through the follow-up period. Specific attention is given to local skin reactions at the electrode site and any potential device-related incidents. All adverse events are documented and reported according to the protocol and regulatory requirements.

Significance and Implications This investigation aims to provide high-level evidence on the efficacy of a non-pharmacologic, neuromodulatory approach to preventing pediatric emergence delirium. Positive results could establish taVNS as a viable strategy to enhance postoperative recovery and safety, with potential implications for broadening the application of bioelectronic medicine in perioperative care.

Inclusion Criteria:

• Children aged 3 to 8 years.
• Patients receiving care at The First Affiliated Hospital of Zhejiang Chinese Medical University with a diagnosis of tonsil and/or adenoid hypertrophy, scheduled for tonsillectomy and/or adenoidectomy under sevoflurane inhalation general anesthesia.
• American Society of Anesthesiologists (ASA) physical status I-II.
• Ability to understand the study procedures and assessment scales, and to communicate effectively with study personnel.

Exclusion Criteria:

• ASA physical status III-IV, or presence of hepatic or renal dysfunction, cardiovascular disease, or endocrine disorders.
• Neuromuscular disorders or dermatitis of the left auricle.
• Recent respiratory infection, developmental delay, or autism spectrum disorder.
• Receipt of specialized care, residence in social welfare institutions, or any other condition that may interfere with study participation.
• Current enrollment in another clinical trial.

De-identified IPD will be available beginning 6 months after publication of the primary results manuscript. Data will be shared with researchers who provide a methodologically sound proposal for use in non-commercial research. Proposals should be directed to the corresponding author. To gain access, requestors will need to sign a data access agreement.

Supporting information (study protocol and statistical analysis plan) will be available beginning 6 months after study completion and for up to 3 years following publication of the primary results.

Access to the study protocol and statistical analysis plan will be granted to academic researchers affiliated with recognized institutions for non-commercial research purposes. Requests should be submitted to the principal investigator by email. Data sharing will require prior approval and signing of a data use agreement.