Validation of the numerical rating scale for pain intensity and unpleasantness in pediatric acute postoperative pain: sensitivity to change over time.

UNLABELLED: This study evaluates the construct validity (including sensitivity to change) of the numerical rating scale (NRS) for pain intensity (I) and unpleasantness (U) and participant pain scale preferences in children/adolescents with acute postoperative pain. Eighty-three children aged 8 to 18 years (mean = 13.8, SD = 2.4) completed 3 pain scales including NRS, Verbal Rating Scale (VRS), and faces scales (Faces Pain Scale-Revised [FPS-R] and Facial Affective Scale [FAS], respectively) for pain intensity (I) and unpleasantness (U) 48 to 72 hours after major surgery, and the NRS, VRS and Functional Disability Index (FDI) 2 weeks after surgery. As predicted, the NRSI correlated highly with the VRSI and FPS-R and the NRSU correlated highly with the VRSU and FAS 48 to 72 hours after surgery. The FDI correlated moderately with the NRS at both time points. Scores on the NRSI and NRSU at 48 to 72 hours were significantly higher than at 2 weeks after surgery. Children found the faces scales the easiest to use while the VRS was liked the least and was the hardest to use. The NRS has adequate evidence of construct validity including sensitivity for both pain intensity and unpleasantness. This study further supports the validity of the NRS as a tool to measure both intensity and unpleasantness of acute pain in children. PERSPECTIVE: This article evaluates the construct validity including sensitivity of the Numerical Rating Scale for pain intensity and pain unpleasantness over time in children after major surgery. The NRS could be used by clinicians to assess these 2 different dimensions of children's pain experience in acute pain settings.

Implicit versus explicit associative learning and experimentally induced placebo hypoalgesia.

The present study examined whether 1) placebo hypoalgesia can be generated through implicit associative learning (ie, conditioning in the absence of conscious awareness) and 2) the magnitude of placebo hypoalgesia changes when expectations about pain are made explicit. The temperature of heat pain stimuli was surreptitiously lowered during conditioning trials for the placebo cream and the magnitude of the placebo effect was assessed during a subsequent set of trials when the temperature was the same for both placebo and control conditions. To assess whether placebo hypoalgesia could be generated from an implicit tactile stimulus, a 2 × 2 design was used with direction of cream application as one factor and verbal information about which cream was being applied as the second factor. A significant placebo effect was observed when participants received verbal information about which cream was being applied but not following implicit conditioning alone. However, 87.5% of those who showed a placebo response as the result of implicit conditioning were able to accurately guess the order of cream application during the final trial, despite a lack of awareness about the sensory manipulation and low confidence in their ratings, suggesting implicit learning in some participants. In summary, implicit associative learning was evident in some participants but it was not sufficient to produce a placebo effect suggesting some level of explicit expectation or cognitive mediation may be necessary. Notably, the placebo response was abolished when expectations were made explicit, suggesting a delicate interplay between attention and expectation.

Reliability and validity of the Child Pain Anxiety Symptoms Scale (CPASS) in a clinical sample of children and adolescents with acute postsurgical pain.

Pain anxiety refers to the cognitive, emotional, physiological, and behavioural reactions to the experience or anticipation of pain. The Child Pain Anxiety Symptoms Scale (CPASS) has recently been developed and validated in a pediatric community sample. The goal of the present study was to examine the psychometric properties of the CPASS in a sample of children and adolescents with acute postsurgical pain. Eightythree children aged 8­18 years (mean 13.8 years, SD 2.4) completed measures of pain anxiety, anxiety sensitivity, pain catastrophizing, anxiety, depression, and pain intensity and unpleasantness 48­72 hours after major surgery; and pain intensity and unpleasantness, pain anxiety, and functional disability approximately 2 weeks after discharge from the hospital. The CPASS showed excellent internal consistency (a = 0.915). Stronger partial correlations of pain anxiety with anxiety sensitivity (r = 0.70) and pain catastrophizing (r = 0.73) compared to pain anxiety with anxiety (r = 0.53) and depression (r = 0.59) suggest excellent construct validity. Pain anxiety was significantly associated with pain intensity (r = 0.44) and unpleasantness (r = 0.32) 48­72 hours after surgery (concurrent validity) and with pain unpleasantness (r = 0.29) and functional disability (r = 0.50; but not pain intensity, r = 0.20) 2 weeks later (predictive validity). The CPASS showed adequate sensitivity to change over time (mean change = 9.52; effect size = 0.49) and good sensitivity and specificity. The results of the present study provide initial validity and reliability of the CPASS in a clinical sample of children and adolescents after major surgery.