The journal of pain : official journal of the American Pain Society
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The purpose of the study was to examine the effect of 3 different application strategies for transcutaneous electrical nerve stimulation (TENS) on neuropathy-induced allodynia and dorsal horn neurotransmitter content. Rats were treated with high-frequency, low-frequency, or a combination of high and low-frequency stimulation. TENS was delivered through self-adhesive electrodes daily for 1 hour to rats with a right-sided chronic constriction injury (CCI). Stimulation was delivered to skin or acupuncture points on the left and mechanical and thermal pain thresholds were assessed in the right hind paw. Neurotransmitter content was assessed bilaterally in the dorsal horn of the spinal cord. Daily, high-frequency or a combination of high- and low-frequency TENS reduced mechanical (P < .001), but not thermal allodynia in the right hind paw when compared with untreated CCI rats. Daily high frequency TENS elevated the dorsal horn synaptosomal content of GABA bilaterally (P < .014) and a combination of high- and low-frequency TENS elevated the dorsal horn content of aspartate (P < .001), glutamate (P < .001) and glycine (P < .001) bilaterally over that seen in untreated CCI rats. The present findings support a contralateral approach to the application of TENS and suggest that distinct strategies for TENS application may differentially alter neurotransmission in the central nervous system. ⋯ Because CCI rats are reminiscent of humans with neuropathy, daily high or a combination of high- and low-frequency TENS may reduce mechanical allodynia in humans with neuropathic pain. Because the 2 intervention strategies produce distinctive alterations in spinal cord neurotransmitter content, each may represent a distinctive option for treatment.
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Clinical Trial
Associations between catastrophizing and endogenous pain-inhibitory processes: sex differences.
Pain catastrophizing is among the most robust predictors of pain outcomes, and a disruption in endogenous pain-inhibitory systems is 1 potential mechanism that may account for increased pain among individuals who report higher pain catastrophizing. Pain catastrophizing may negatively influence diffuse noxious inhibitory controls (DNIC), a measure of endogenous pain inhibition, through complex anatomical circuitry linking cortical responses to pain with processes that modulate pain. The current study examined whether DNIC mediated the relationship between catastrophizing and pain among 35 healthy young adults and examined the moderating effects of sex to determine whether the magnitude or direction of associations differed among men and women. DNIC was assessed using pressure pain thresholds on the forearm before and during a cold pressor task. Using bias-corrected bootstrapped confidence intervals, results showed that diminished DNIC was a significant partial mediator of the relation between greater pain-related catastrophizing and more severe pain ratings. Participant sex moderated these associations; higher catastrophizing predicted lower DNIC for men and women, however, the effect of catastrophizing on pain ratings was partially mediated by DNIC for women only. These findings further support the primary role of pain catastrophizing in modulation of pain outcomes. ⋯ These findings support the hypothesis that the heightened pain reported by individuals higher in pain catastrophizing may be related to a disruption in the endogenous modulation of pain, operationalized by assessing DNIC. Whether interventions that reduce pain catastrophizing affect pain outcomes via effects on DNIC is in need of investigation.
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Chronic noncancer pain is common and use of opioids is increasing. Previously published guidelines on use of opioids for chronic noncancer pain have been based primarily on expert consensus due to lack of strong evidence. We conducted searches on Ovid MEDLINE and the Cochrane databases through July 2008 to identify studies that addressed one or more of 37 Key Questions that a multidisciplinary expert panel identified as important to be answered to generate evidence-based recommendations on the use of opioids for chronic noncancer pain. A total of 14 systematic reviews, 38 randomized trials not included in a previously published systematic review, and 13 other studies met inclusion criteria. Almost all of the randomized trials of opioids for chronic noncancer pain were short-term efficacy studies. Critical research gaps on use of opioids for chronic noncancer pain include: lack of effectiveness studies on long-term benefits and harms of opioids (including drug abuse, addiction, and diversion); insufficient evidence to draw strong conclusions about optimal approaches to risk stratification, monitoring, or initiation and titration of opioid therapy; and lack of evidence on the utility of informed consent and opioid management plans, the utility of opioid rotation, the benefits and harms specific to methadone or higher doses of opioids, and treatment of patients with chronic noncancer pain at higher risk for drug abuse or misuse. ⋯ Currently, clinical decisions regarding the use of opioids for chronic noncancer pain need to be made based on weak evidence. Research funding priorities need to be set to address these critical research needs if the care of patients with chronic noncancer pain is to improve.
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Multicenter Study Comparative Study
Does the Neonatal Facial Coding System differentiate between infants experiencing pain-related and non-pain-related distress?
The Neonatal Facial Coding System (NFCS) is widely accepted as a measure of infant pain-related distress in known pain-specific contexts. It has clearly shown the ability to distinguish between facial reactivity in no-pain and pain-related situations. The primary purpose of this study was to explore whether NFCS differentiates between pain-related and non-pain-related distress. Two groups of 35 infants (1 group was distressed before injection whereas the other group was not distressed before injection) were coded using NFCS before and after an immunization procedure. Within-group analyses of infants who were distressed before immunization suggested that NFCS was not able to discriminate between pain-related and non-pain-related distress. However, between-group analyses showed NFCS discriminated between potential gradations of distress in infants after immunization. Results suggest that NFCS has the ability to discriminate between intensities of distress but not between pain-related and non-pain-related distress. ⋯ Adding to the NFCS validity literature, this study suggests that while able to distinguish between no-distress and pain-related distress, facial actions of NFCS may not distinguish between pain-related and non-pain-related distress expressions. However, NFCS was able to discern infants presumed to have higher pain-related distress due to experiencing pre-needle distress.
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This investigation determined the psychometric properties and acceptability of an animated face scale presented on a hand-held computer as a means to measure pediatric pain and mood. In study 1, 79 hospitalized, pediatric patients indicated their levels of pain by adjusting the expression of an animated cartoon face. The first objective was to determine feasibility, concurrent validity, and acceptability of the method. All patients were tested both with the Computer Face Scale and the poster format of the Wong-Baker Faces Scale. A second objective was to evaluate test-retest reliability of the method. In study 2, 50 hospitalized, pediatric patients were tested on 2 occasions, but in this case the patients used the Computer Face Scale to indicate both their pain (how much they hurt) and their mood (how they felt). Children in study 1 were able to use the Computer Face Scale to express relative amounts of pain/hurt; the method showed concurrent validity with the Wong-Baker Face Scale; and most children expressed a preference for the Computer Face Scale. The method also showed adequate test-retest reliability. In study 2, adequate test-retest reliability was demonstrated for ratings of both pain and mood. ⋯ The Computer Face Scale allows the health provider to obtain reliable and valid measures of pediatric pain and mood. The method can be understood and used by children as young as 3 years and is appropriate for use with adults.