Pupillary dilation reflex and behavioural pain scale: Study of diagnostic test.

Background: The objective of this study was to assess the value of the pupillary dilation reflex as an assessment pain tool in critically ill patients. It is important to continue working for the well-being and security of critically ill patients.

Methods: We studied the diagnostic accuracy of the pupillary dilation reflex against the Behavioral Pain Scale. Inclusion criteria were: age greater than 18, receiving mechanical ventilation, with a basal score of the Behavioural Pain Scale of three and a Richmond Agitation and Sedation score between -1 and -4. We studied the responses to a non-painful stimulus, four calibrated stimuli, after a tracheal aspiration and with and without pain. The receiver operating curve was plotted and we calculated the area under the curve. We identified the cut-off points showing the highest sensitivity and specificity and studied diagnostic performance based on negative predictive value, positive predictive value, and accuracy. These were reported with their 95% confidence intervals.

Results: 183 measurements were performed. An AUC of 0.88(95% CI 0.83-0.94) was obtained. The pupillary dilation reflex of 11.5% had a sensitivity of 89.8%(95% CI 78.2-95.6) and a specificity of 78.4%(95% CI 70.6-84.5) with an accuracy of 81.4(75.2-86.4). The pupillary dilation reflex detected nociceptive pain response in 15.8% of the measurements that did not show pain according to the Behavioural Pain Scale.

Conclusions: Pupillometry may be a valid alternative for identifying pain in critically ill patients.