The journal of pain : official journal of the American Pain Society
-
A number of negative affect-related constructs are important in pain. Some are general, such as anxiety, depression and negative affectivity, whereas others are more specifically pain-related (eg, fear of pain, pain anxiety, and pain catastrophizing). In addition, some more specific fear-related constructs, such as anxiety sensitivity, illness/injury sensitivity, and fear of negative evaluation have emerged as important to pain. Although these various constructs are considered conceptually separate, there is likely to be overlap between them. Since the extent of this overlap is unknown, the aim of the current study was to investigate these constructs in 1 sample in order to identify their common and unique features. Frequently used psychological measures were completed by 508 pain-free participants. Principal components analysis resulted in the extraction of three components: 1) General distress; 2) Fear of pain from injury/insult; and 3) Cognitive intrusion of pain. The results presented here suggest that there is indeed commonality between constructs, which may be due to either an overlap between items within measures or to close conceptual relatedness. The implications of these core dimensions are discussed with reference to future research and theory. ⋯ This article explores the relationships between various negative-affect pain-related measures and discusses the results from a principal components analysis. The findings show that some questionnaires may measure the same latent construct. A measure could be developed to measure these 3 core components more concisely for both clinical and research purposes.
-
Ambiguous or blunted responses to sensory and painful stimuli among individuals with severe intellectual disabilities and comorbid communicative impairments put them at risk for having their experience of pain discounted and their expression of pain misinterpreted. Valid measurement procedures of behavioral expression are critical for this vulnerable group of individuals. We investigated a sham-controlled sensory-testing protocol as an approach to guard against observer bias during nonverbal behavioral recording for individuals with intellectual disabilities. Participants were 44 (52% male) adults (mean age = 46, sd = 10) with moderate (14%) and severe to profound (86%) intellectual impairment. The facial behavior of the participants before, during, and after 5 sensory-stimulation modalities (pin prick, light touch, deep pressure, cool, warm) was coded by 3 raters using the Facial Action Coding System (FACS). For each participant, the 5 active sensory trials were randomized with sham trials during which no stimulation was applied. Observers were blinded to active vs sham stimulation status. FACS scores increased significantly during active sensory trials (P < .05) compared with sham trials. There were significant effects for gender, with females more expressive than males (P < .05). There were also significant effects for the presence of self-injurious behavior (SIB), with individuals with SIB more expressive than individuals without SIB (P < .05). The results suggest that the procedure was valid (ie, distinguished between active vs sham sensory stimulation) and provides additional evidence that individuals with significant intellectual impairments are sensitive to tactile stimulation consistent with quantitative sensory-testing protocols. ⋯ This article presents a novel application of a modified approach to quantitative sensory testing for nonverbal adults with intellectual and developmental disabilities. This approach could be important in helping determine sensory issues related to tactile and nociceptive processes among a highly vulnerable group of individuals.
-
Comparative Study
Comparison of the cold pressor test and contact thermode-delivered cold stimuli for the assessment of cold pain sensitivity.
Sensitivity to suprathreshold cold pain stimuli constitutes an important part of comprehensive pain sensitivity testing and can be assessed by the cold pressor test or by using a contact thermode-based testing device. One major difference between the 2 methods is the size of the surface area stimulated, which is thought to affect both recruitment of endogenous pain control mechanisms and vasomotor reactions. It is therefore not clear if the 2 methods can be used interchangeably for the assessment of cold pain. Here we applied 60-second-long stimuli at approximately 3 degrees C to the hands of 47 subjects by both methods. Pain intensity ratings (on a scale from 0 to 10) were significantly higher in the cold pressor test than in the thermode cold test (6.3 +/- 1.8 vs 3.9 +/- 2), associated with a higher rate of dropouts within the 60 seconds (64 vs 11%). Nonetheless, pain intensity ratings obtained with both methods were highly correlated (r = .70). However, the thermode cold test shared a larger amount of variance with 1 or more of the other pain intensity rating tests (phasic and tonic heat, pinprick) than the cold pressor test (53% vs 30%) while the cold pressor test contained a larger proportion of unique variance (39 vs 26%). ⋯ This article compares 2 methods of cold pain assessment in humans and analyzes their relationship to heat and pinprick pain. It could help researchers select the appropriate cold pain test for their study. It may also promote our understanding of commonalities and differences between different pain modalities.
-
Intramuscular injection of hypertonic saline produces a dull ache that is felt in the muscle belly but also often refers into distal structures. We have previously observed in 2 subjects that the pattern of pain referral alters during painful stimuli separated by a week. In this investigation, we tested the hypothesis that the intensity and area of pain in the local and referred regions exhibits plasticity when an identical noxious stimulus is delivered to the same site over sequential trials. Bolus 1 mL intramuscular injections of 5% hypertonic saline were made into the same site of the tibialis anterior (TA) muscle on the same day each week for 4 consecutive weeks. Twenty-one subjects mapped the areas of local and referred pain and rated the intensities on a visual analog scale every 30 seconds until the cessation of pain. Over 4 weeks there was a progressive reduction in the area and intensity of local pain and a reciprocal increase in the expression of referred pain. We conclude that the decrease in perceived local pain and increase in perceived referred pain reflects plastic processes occurring centrally. ⋯ What happens to the intensity of pain induced by repeated noxious stimuli over time? Does it stay the same, increase or decrease? Here we show that weekly injections of hypertonic saline into the tibialis anterior cause decreases in local but increases in referred pain, suggesting central changes in processing noxious inputs.