Pupillometry in Identifying Risk of Postoperative Opioid-induced Respiratory Depression in Children Undergoing Tonsillectomy

This is a prospective, observational cohort study designed to evaluate the relationship between perioperative pupillary responses and postoperative opioid-induced respiratory depression (OIRD) in pediatric patients undergoing tonsillectomy.

Approximately 300 participants aged 3 to less than 18 years will be enrolled across participating clinical sites. Pupillometry measurements will be obtained using a portable, automated infrared pupillometer at predefined perioperative time points, including preoperative baseline, intraoperative periods, and postoperative recovery. Measurements will include resting pupil diameter, pupillary light reflex parameters (including percent constriction, constriction velocity, dilation velocity, and latency), and pupillary unrest in ambient light.

Pupillometry measurements will be collected solely for research purposes and will not be used to guide clinical management. All patients will receive standard perioperative care as determined by the clinical team.

The primary outcome is the occurrence of postoperative opioid-induced respiratory depression, defined as persistent oxygen desaturation (SpO2 <90%) or respiratory rate <8 breaths per minute in the absence of airway obstruction in the post-anesthesia care unit. Secondary outcomes include opioid consumption, sedation scores, pain scores, and postoperative complications such as nausea and vomiting.

Data will be analyzed to assess the association between pupillary response parameters and the occurrence of respiratory depression, and to support development of predictive models for identifying patients at increased risk of opioid-related adverse events.

Inclusion criteria

• Age 3 to less than 18 years
• Scheduled to undergo tonsillectomy with or without adenoidectomy
• Planned postoperative recovery in a monitored clinical setting (e.g., post-anesthesia care unit)
• Ability to obtain informed consent from parent or legal guardian and assent from the participant when developmentally appropriate

Exclusion criteria

• Known neurologic or ophthalmologic conditions that may affect pupillary function
• Use of medications known to significantly alter pupillary response outside of standard perioperative care
• Inability to obtain adequate pupillometry measurements (e.g., due to eye injury or inability to safely perform measurement)
• Patients not receiving opioids as part of perioperative care
• Any condition that, in the opinion of the investigator, would interfere with study participation or data interpretation