The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Effects of focusing and distraction on cold pressor-induced pain in chronic back pain patients and control subjects.
Previous studies showed equivocal findings regarding the efficacy of focused attention and distraction to experimental pain. This study examined the relative efficacy of these strategies on perception of cold pressor pain in 41 chronic back pain patients and 41 healthy control participants. Participants were randomized to the 2 strategies and then completed a 7-minute cold pressor test. Pain intensity and discomfort ratings were obtained during the task. Participants who completed the first task were asked to complete a second cold pressor task without instructions. Pain and discomfort ratings differed by condition across time. In the distraction condition, pain levels started low but continued to rise throughout the cold pressor immersion, whereas in the focused attention condition, pain levels started higher, rose less quickly, and then decreased from the middle of the task. Focused attention was associated with higher pain and lower completion rates in chronic pain patients compared with healthy control subjects. Focused attention might therefore not be an effective intervention strategy for individuals with chronic back pain. Finally, in the second cold pressor test, patients' pain reports rose more rapidly than those of healthy control subjects. The results of this study can be explained in terms of differences in cognitive appraisal between pain patients and healthy control participants. ⋯ Marked differences were found between chronic back pain patients and control participants regarding focused attention as compared with distraction as a means of coping with cold pressor-induced pain. These differences underline the importance of taking into account previous experience with pain when recommending strategies to cope with painful procedures.
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Clinical practice guidelines recommend that numeric rating scales be used to document the severity of perceived pain, yet patients and clinicians often opt to use simpler classification systems such as mild, moderate, or severe. To assess how well the numeric scales correlate with the tri-level classification system for describing pain severity, we conducted a subanalysis of a larger population-based study of pain management preferences. Our primary objective was to identify the numeric boundaries used by 287 adults to describe pain as mild, moderate, or severe. We examined differences in the means of the upper and lower limits for mild, moderate, and severe pain according to demographic characteristics and type of pain. Ranges reported for each pain level were 1.3 to 3.6 (mild), 4.3 to 6.5 (moderate), and 7.5 to 9.8 (severe). The primary finding was that "healthy" community adults rated the pain severity cutpoints much as patients with clinical pain did, 1 to 4 for mild, 5 to 6 for moderate, and 7 to 10 for severe. These results suggest that numeric rating scales can be used in clinical practice with both patients and community-dwelling adults. Our findings also support encouraging the general public to use a 0 to 10 scale to rate their pain intensity. ⋯ Methods used to describe numeric cutpoints for mild, moderate, and severe pain were applied to community adults. Having standard categories to describe pain severity might increase clinicians' confidence in using a numeric scale to make treatment decisions. Further studies of cutpoint methodology and its clinical importance are warranted.
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Pain draws on attentional resources, thereby disturbing the pursuit of ongoing activities. Several studies have made use of the primary task paradigm to study the disruptive function of pain on attention. In this paradigm, participants perform an attentionally demanding task, while they are occasionally distracted by mild electrical stimulation. Deterioration in task performance (in terms of speed and accuracy) is then taken as an index of attentional interference. One major finding with this paradigm was that pain catastrophizing enhances attentional interference. The current study aimed to replicate this finding and to explore the possible influence of anxiety sensitivity and injury/illness sensitivity on attentional interference. Healthy volunteers (n = 48) performed an auditory discrimination task and were thereby occasionally distracted by low electrocutaneous stimulations. The performance on the discrimination task was subsequently related to participants' scores on the Pain Catastrophizing Scale, the Anxiety Sensitivity Index, and the Injury/illness Sensitivity Index. We were unable to demonstrate an association of either injury/illness sensitivity or anxiety sensitivity with attentional interference. Results did, however, confirm the finding that pain catastrophizing enhances attentional interference. ⋯ The present study showed that pain disrupts ongoing activities. This effect is enlarged in those with high levels of pain catastrophizing and is related to the threatening nature of pain stimuli. The role of anxiety sensitivity and injury/illness sensitivity seems to differ from the role of catastrophizing and needs further research.
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The effect of pain processing on attention capacity during visual search was examined in 2 experiments. In the first experiment, we investigated whether pain draws on the same limited resources as attentional task performance. It was hypothesized that pain would negatively affect task performance under different load manipulations. Low and high load conditions of a visual search task were presented in a mixed design combined with a painfully cold or neutral cold pressor test. Performance was not affected by pain. In experiment 2, low and high load conditions were separated in different blocks to study whether pain perception was affected when task load could be anticipated. Again, pain did not significantly affect task performance. In contrast, subjective pain intensity scores were significantly lower after performing the high load compared with the low load condition. Simultaneous recordings of event-related potentials indicated an increased negativity during the pain compared with the control condition. Also, in the early (350 to 450 msec) interval of event-related potentials, an increase in negativity was found for the high load compared with the low load condition. Topographic distributions suggested that pain and task load are mediated by qualitatively different resources. ⋯ Our findings indicate that highly demanding attentional task performance and pain processing interfere as a result of difficulties in allocating attention. The clinical relevance of this finding is that performing a highly demanding task might distract attention from pain.
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Devices designed for mechanical pain threshold studies are often difficult to implement. The purpose of this study was to investigate a simple tool based on calibrated forceps to induce quantifiable mechanical stimulation in the rat on a linear scale. The most suitable protocol was tested by determining the effects of 3 repetitive measurements on both hind paws, respectively, during long-term (9 days), mid-term (1 day), and short-term (2 hours). Only threshold increase related to weight gain over long-term was observed, suggesting that moderate rat training can be used. The capacity of the device to reveal hyperalgesia was tested in a model of carrageenan-induced inflammation in the hind paw. The hyperalgesia was maximal 6 hours after carrageenan injection and progressively decreased. Similar, although more variable, responses were observed with von Frey filaments. Morphine-induced analgesia resulted in a dose-dependent increase of paw threshold. Tolerance to morphine administrated on a once daily schedule (10 mg/kg) during 5 days was revealed by a significant decrease in analgesia by day 3. Taken together, these results demonstrated accuracy of this device for easy, fast, and reproducible measure of mechanical pain threshold on rat limbs. Moreover, it allows the performance of rat testing with minimal constraint, which reduces data variability. ⋯ The calibrated forceps is an easy to use device well-suited to rapidly test mechanical pain threshold with accuracy. It is well-designed for preclinical behavioral screening of noxious or analgesic properties of molecules.