• Elie Kantor, Philippe Montravers, Dan Longrois, and Jean Guglielminotti.
• From the Département d'Anesthésie-Réanimation, Hôpital Bichat, AP-HP (EK, PM, DL, JG), Université Paris Diderot, Sorbonne Paris Cité (PM, DL, JG) and INSERM, UMR 738 (JG), Paris, France.
• Eur J Anaesthesiol. 2014 Feb 1;31(2):91-7.

BackgroundPatients assess their own pain with a numerical rating scale (NRS). In the postanaesthesia care unit (PACU), NRS helps to determine and monitor analgesic administration, but is useless in patients who are unable to communicate. In non-PACU patients, acute pain increases pupillary diameter and pupillary light reflex amplitude (PLRA), the difference between pupillary diameter before and after light stimulation.ObjectivesTo study the association between postoperative pain (NRS) and pupillary diameter or PLRA in PACU patients after routine anaesthetic care.DesignCross-sectional cohort study.SettingBichat-Claude Bernard Hospital, Paris.PatientsOne hundred and forty-five patients undergoing planned surgery under general anaesthesia.InterventionsNRS, pupillary diameter and PLRA were measured on arrival in the PACU. When NRS was more than 4, intravenous morphine titration was started and a second measurement performed.Main Outcome MeasuresAssociation between NRS and pupillary diameter or PLRA was assessed with Pearson correlation coefficient (r) as was association between changes in these variables after morphine titration.ResultsMean NRS was 4.7, and was more than 4 in 79 patients (55%). No statistically significant association was observed between NRS and pupillary diameter (r = 0.10, P = 0.54) or PLRA (r = 0.03, P = 0.72). Twenty-seven patients (19%) received morphine titration with significant decreases in NRS, pupillary diameter and PLRA afterwards. No association was observed between NRS changes and pupillary diameter or PLRA changes.ConclusionAcute postoperative pain is not associated with pupillary diameter or PLRA. Further research is required to develop tools to assess pain in the PACU.

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