The postoperative recovery period following general anesthesia has been associated with a 30%-50% incidence of postoperative respiratory adverse events (PRAEs) in pediatric populations, including laryngospasm, airway obstruction, and hypoxemia. Despite the limited effects of existing pharmacological and operative interventions, positional optimization (e.g., lateral or semirecumbent position) may play a potential role by decreasing airway resistance and improving oxygenation. However, evidence-based evidence for its use in pediatric populations is still lacking, necessitating the urgent need for randomized controlled trials.

This study is a multi-center, prospective, RCT conducted at four tertiary hospitals in China. It will be planned to include 350 subjects who meet the inclusion criteria and will be randomly divided into the lateral position and supine position group in a 1:1 ratio by the method of block group randomization stratified by centers. In the supine position group, the children will be extubated at the end of the procedure and observed in the decubitus position until the patient's Aldrete score was >9 and they left the PACU, whereas in the lateral position group, the children will be extubated and observed in the head-up 30° lateral position. The primary outcome is the incidence of PRAEs. Secondary outcomes included frequency of PRAE, number of airway devices used during the postoperative recovery period, time to tracheal extubation, length of stay in the recovery room, and incidence of PRAE at 24 hours and 7 days. postoperatively. Safety outcomes include the incidence of peripheral IV access dislodgement, monitoring device detachment rate, and patient falls rate. Exploratory outcomes comprise pain levels (assessed via the FLACC scale), agitation scores (PAED scale), sedation scores (Ramsay scale), and PONV scores, all evaluated at postoperative extubation and PACU discharge.

Inclusion criteria:

1. Subjects aged 1-6 years old without gender limit.
2. Scheduled for an ambulatory adenotonsillectomy under general anesthesia.
3. American Society of Anesthesiologists (ASA) classification grade I or II.
4. Informed consent obtained from the patients' parents or legal guardians, who have expressed willingness to cooperate.

Exclusion criteria:

1. Presence of concomitant cardiac or pulmonary dysfunction or other significant systemic comorbidities.
2. History of difficult airway management or congenital/acquired structural anomalies of the airway.
3. Active respiratory tract infection within 30 days preceding surgery.
4. Preoperative neurological disorders or developmental abnormalities.
5. Intraoperative occurrence of major complications necessitating deviation from the planned anesthesia protocol or surgical procedure.

Given the intervention's nature, full blinding was impossible; only postoperative data collectors and analysts were blinded. To minimize potential bias, we plan to maintain blinding among participants, anesthesiologists and surgeons in the operating room, the data collectors who conduct inpatient and telephone follow-up visits and data analysts. However, blinding could not be preserved for investigators, post-anesthesia care unit (PACU) outcome measure recorders, care providers in the PACU.