Three clinical scales (the Nociception Coma Scale adapted for Intubated patients [NCS-I], its Revised version [NCS-R-I], and the Behavioral Pain Scale [BPS]) and videopupillometry were compared for measuring pain in intubated, noncommunicating, critically ill, brain-injured patients. Pain assessment was performed before, during, just after, and 5 minutes after 3 procedures: the reference non-nociceptive procedure (assessment of the Richmond Agitation Sedation Scale) and 2 nociceptive procedures (turning and tracheal suctioning). The primary endpoint was construct validity (discriminant and criterion validation), determined by comparing pain measurements between different times/procedures. Secondary endpoints were internal consistency, inter-rater reliability, and feasibility. Fifty patients (54% women, median age 63 years [56-68]) were included 13 [7-24] days after brain injury (76% hemorrhagic or ischemic strokes). All tools increased significantly more (P < 0.001) during the nociceptive procedures vs the non-nociceptive procedure. The BPS was the only pain tool that did not increase significantly during the non-nociceptive procedure (P = 0.41), suggesting that it was the most discriminant tool. The BPS, NCS-I, and NCS-R-I were good predictors of nociception with areas under the curves ≥0.96, contrary to videopupillometry (area under the curve = 0.67). The BPS, NCS-I, and NCS-I-R had high inter-rater reliabilities (weighted kappa = 0.86, 0.82 and 0.84, respectively). Internal consistency was moderate (>0.60) for all pain scales. Factor analysis represented a majority of information on a first dimension, with motor domains represented on a second dimension. Scale feasibility was better for the NCS-I and NCS-R-I than for the BPS. In conclusion, the BPS, NCS-I, and NCS-R-I are valid, reliable, and acceptable pain scales for use in intubated critically ill, brain-injured patients, unlike videopupillometry. Future research requires tool design centered on domains of observation adapted to this very specific population.
Trial registration: ClinicalTrials.gov NCT02830256.