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

Abstract

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.

Keywords: Analgesia; Pain; Pharmacology; Technology.

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Figures

Figure 1

The association of maximum pupil constriction velocity with pain intensity determined by patient self-report using a validated visual analog scale (VAS). The association was statistically significant (p

Figure 2

The association of the percent of pupil constriction with pain intensity determined by patient self-report using a validated visual analog scale (VAS). The association was statistically significant (p

Figure 3

The relationship between pain intensity and maximum constriction velocity over time for the individual with the highest and lowest relationship between these variables.

Figure 4

The relationship between pain intensity and maximum constriction velocity over time for the individual with the lowest relationship between these variables.

Figure 5

The association between baseline pupil size and daily drug dose (expressed as mcg/kg morphine equivalents). The association was statistically significant (p