Author(s): Kantor E, Montravers P, Longrois D, Guglielminotti J
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Abstract BACKGROUND: Patients 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. OBJECTIVES: To study the association between postoperative pain (NRS) and pupillary diameter or PLRA in PACU patients after routine anaesthetic care. DESIGN: Cross-sectional cohort study. SETTING: Bichat-Claude Bernard Hospital, Paris. PATIENTS: One hundred and forty-five patients undergoing planned surgery under general anaesthesia. INTERVENTIONS: NRS, 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 MEASURES: Association 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. RESULTS: Mean 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. CONCLUSION: Acute postoperative pain is not associated with pupillary diameter or PLRA. Further research is required to develop tools to assess pain in the PACU.
This article was published in Eur J Anaesthesiol
and referenced in Journal of Anesthesia & Clinical Research