This study will evaluate whether quantitative pupillometry measurements can be used to identify children at risk for postoperative opioid-induced respiratory depression (OIRD) following tonsillectomy. Opioid-induced respiratory depression is a serious and potentially life-threatening complication that can occur after surgery, and current monitoring approaches are limited in their ability to predict which patients are at highest risk.

In this prospective observational cohort study, approximately 300 pediatric patients undergoing tonsillectomy will undergo non-invasive pupillometry measurements at defined perioperative time points, including preoperative, intraoperative, and postoperative periods. Pupillometry measurements will be collected using a commercially available, FDA-regulated infrared pupillometer. These measurements will include pupil size, constriction and dilation velocities, and latency in response to light stimulation.

Pupillometry data will be collected for research purposes only and will not be used to guide clinical care or treatment decisions. Standard clinical care will not be altered as part of this study. Clinical outcomes, including the occurrence of postoperative opioid-induced respiratory depression, opioid use, sedation levels, pain scores, and other postoperative events, will be recorded from the medical record.

The goal of this study is to evaluate the relationship between pupillary response patterns and the occurrence of postoperative respiratory depression, and to support the development of predictive models that may improve early identification of patients at risk for opioid-related adverse events.

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

The study population will consist of pediatric patients aged 3 to less than 18 years undergoing tonsillectomy with or without adenoidectomy at participating clinical sites. Participants will be enrolled from routine clinical care settings and will receive standard perioperative management. The study will include patients across a range of clinical characteristics representative of the typical pediatric tonsillectomy population.

The study team has not yet determined whether individual participant data will be shared. Any future data sharing will be evaluated following study completion and will consider participant privacy, institutional policies, intellectual property considerations, and applicable NIH and regulatory requirements.