Pain
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Psychophysical methods were used to investigate pain in human subjects elicited by controlled freezing of the skin using a novel vortex thermode. When cooling stimuli delivered with a small thermode (7 mm diameter) exceeded the normal cold pain threshold into the sub-zero temperature range (-5 to -11 degrees C), all subjects reported an intense, sharp stinging pain sensation which occurred suddenly and was readily differentiated from normal cold pain. The onset of this stinging 'freezing' pain was closely correlated with a sudden increase in skin temperature beneath the thermode of 4.77+/-0.86 degrees C (+/-SD) associated with the phase transition of supercooled water to ice. ⋯ The changes in thermal sensitivity were not accompanied by consistent changes in mechanical sensitivity. These results indicate that a characteristic sharp, stinging pain is reliably evoked abruptly at the phase transition of supercooled skin water to ice The ensuing brief decrease in cold pain threshold with burning quality, coupled with decreased sensitivity to cold, are speculated to reflect a central disinhibition of C-fiber nociceptor input due to reduced cold fiber activity. These effects may be relevant to frostbite, and distinguish themselves from the more pronounced thermal and mechanical hyperalgesia seen following intense freeze lesion of the skin.
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Fillingim and Maixner (Fillingim, R. B. and Maixner, W., Pain Forum, 4(4) (1995) 209-221) recently reviewed the body of literature examining possible sex differences in responses to experimentally induced noxious stimulation. Using a 'box score' methodology, they concluded the literature supports sex differences in response to noxious stimuli, with females displaying greater sensitivity. ⋯ Given the estimated effect size of 0.55 threshold or 0.57 for tolerance, 41 subjects per group are necessary to provide adequate power (0.70) to test for this difference. Of the 34 studies reviewed by Fillingim and Maixner, only seven were conducted with groups of this magnitude. The results of this study compels to caution authors to obtain adequate sample sizes and hope that this meta-analytic review can aid in the determination of sample size for future studies.
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Randomized Controlled Trial Clinical Trial
Examiner expectancy effects in the measurement of pressure pain thresholds.
The ascending Method of Limits, used for the determination of pressure pain thresholds (PPT), is not a psychophysically robust method. The present study sought to determine if the examiner's expectancy, based on whether the measurement site was clinically 'painful' or 'non-painful', would bias the obtained PPT values. Twenty-eight patients with facial or temporal area pain served as subjects, and in each subject, a pain site and a control site were identified and marked. ⋯ Manipulating the examiner's prior knowledge of the measurement site's characteristics significantly lowered the obtained PPT values for control sites but did not significantly alter the PPT at the clinically painful sites. Nevertheless, the pain sites still had significantly lower PPTs than did control sites. We conclude that: (i) PPTs at pain sites are robust to a major source of measurement bias associated with the ascending Method of Limits; (ii) measurement order and knowledge of measurement site characteristics can influence obtained PPT; and (iii) the common protocol in which the examiner monitors the amount of pressure during PPT measurement in order to control the force application rate may serve as a mechanism that can bias the obtained values.
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Randomized Controlled Trial Clinical Trial
Double-blind evaluation of short-term analgesic efficacy of orally administered diclofenac, diclofenac plus codeine, and diclofenac plus imipramine in chronic cancer pain.
A prospective double-blind randomized trial was conducted on 184 cancer patients with moderate to severe chronic pain to evaluate the analgesic efficacy and tolerability of diclofenac alone (50 mg q.i.d.) or in combination with a weak opioid (codeine 40 mg q.i.d.), or with an anti-depressant (imipramine, 10 or 25 mg t.i.d.). All demographic and clinical characteristics including cancer type, presence of bone metastases, baseline pain severity, neuropathic and nociceptive pain, and depressive state, were well balanced between the three treatment groups. ⋯ Patients on imipramine plus diclofenac and on placebo plus diclofenac were withdrawn mainly for inadequate efficacy, while patients on codeine plus diclofenac discontinued equally for inadequate efficacy or adverse events. In conclusion, in a short-term evaluation the addition of a tricyclic anti-depressant or a weak opioid to diclofenac did not provide further analgesia with respect to diclofenac administration alone.
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Randomized Controlled Trial Clinical Trial
Randomized controlled trial of a community-based psychoeducation program for the self-management of chronic pain.
Although chronic pain is a frequent cause of suffering and disability and is costly to society, there continues to be limited access to specialty pain clinic services. Hence, there is a need for cost-effective, accessible interventions that will help people find ways to better manage this difficult problem. This randomized controlled trial examined the effect of a low-cost, community-based, nurse-delivered, group psychoeducation program entitled the Chronic Pain Self-Management Program (CPSMP). ⋯ Results of intention-to-treat analysis indicated that the treatment group made significant short-term improvements in pain, dependency, vitality, aspects of role functioning, life satisfaction and in self-efficacy and resourcefulness as compared to the wait-list control group. Because it has a standard protocol, this intervention has the potential to be reliably delivered at low cost in varied urban and rural community settings and hence be more widely accessible to a greater number of people suffering from chronic pain than is currently the case with more specialized pain clinic services. Based on the results of this study, further research evaluating the long-term impact and potential cost savings to the individual and to the health care system is warranted.