Pupillometry: a non-invasive technique for pain assessment in paediatric patients

Objective Pupillometry has been used to assess pain intensity and response to analgesic medications in adults. The aim of this observational study was to explore proof of concept for the use of this technique in paediatric patients. Changes in pupil parameters before and after opioid exposure also were evaluated. Design and setting This was a single-centre, prospective study conducted at an academic paediatric medical centre. Patients Children 9-17 years of age undergoing elective surgical correction of pectus excavatum were enrolled into a protocol approved by the human ethical committee (institutional review board). Interventions Pupil size and reactivity were measured using a handheld pupillometer. Pain was assessed using age-appropriate, validated pain self-report scales. Results Thirty patients were enrolled. Each point change on a 10 cm visual analogue pain intensity scale was associated with a statistically significant mean change of 0.11 mm/s in maximum pupil constriction velocity, and of approximately 0.4% in pupil diameter. As expected, there was an association between total opioid dose (expressed as morphine equivalents) and pupil diameter. Age, sex and baseline anxiety scores did not correlate significantly with pupillary response. Conclusions The association of maximum pupillary constriction velocity and diameter with pain scores illustrates the potential for using pupillometry as a non-invasive method to objectively quantitate pain response/ intensity in children. The technique holds promise as a pharmacodynamic 'tool' to assess opioid response in paediatric patients.