The journal of pain : official journal of the American Pain Society
-
Case Reports
The contribution of sympathetic mechanisms to postamputation phantom and residual limb pain: a pilot study.
Postamputation pain (PAP) affects over 60% of major limb amputees. One of the main challenges in treating PAP is the difficulty involved in identifying pain mechanism(s), which pertains to both residual limb pain (RLP) and phantom limb pain (PLP). In this study, sympathetic blocks were performed on 17 major limb amputees refractory to treatment, including 2 placebo-controlled blocks done for bilateral amputations. One hour postinjection, mean RLP scores at rest declined from 5.2 (SD 2.8) to 2.8 (SD 2.6) (P = .0002), and PLP decreased from 5.3 (SD 3.1) to 2.3 (SD 2.1) (P = .0009). By 1 week, mean pain scores for RLP and PLP were 4.3 (SD 2.9) and 4.2 (SD 3.0), respectively. Overall, 8 of 16 (50%) patients experienced ≥50% reduction in RLP 1-hour postinjection, with the beneficial effects being maintained at 1 and 8 weeks in 4 and 1 patient(s), respectively. For PLP, 8 of 15 (53%) patients obtained ≥50% decrease in pain 1-hour postblock, with these numbers decreasing to 2 patients at both 1 and 8 weeks. In the 2 bilateral amputees who received controlled injections, mean PLP and RLP at rest scores went from 4.0 and 3.3 to 4.0 and 2.5 1-hour postblock, respectively, on the placebo side. On the treatment side, mean PLP and RLP scores decreased from 7.5 and 6.5, respectively, to 0. ⋯ The results of this study suggest that sympathetic mechanisms play a role in PLP and to a lesser extent, RLP, but that blocks confer long-term benefits in only a small percentage of patients.
-
Genetic studies have become indispensable in understanding pain mechanisms, shedding light on the role of monoamine pathways in pain modulation. The present study was aimed to explore the relationship between functional polymorphisms in serotonin and dopamine-related genes and pain modulation. Two paradigms of pain modulation were administered to 191 healthy participants in a random order: Conditioned Pain Modulation in response to painful stimuli (CPM(painful)) tested by the coadministration of repeated short painful heat stimuli and a conditioning tonic cold pain stimulation; and Conditioned Pain Modulation in response to nonpainful stimuli (CPM(nonpainful)) tested similarly, except for using a painless conditioning stimulation. Using the Transmission Disequilibrium Test (TDT), functional variable number of tandem repeat (VNTR) polymorphisms of the following candidate genes were studied: 1) serotonin transporter (5-HTTLPR); 2) dopamine transporter (DAT1); 3) dopamine receptor 4 (DRD4); and 4) monoamine oxidase A (MAOA). DNA samples from both participants and their parents were analyzed. A significant association was found between CPM(nonpainful) and the 5-HTTLPR polymorphism (P = .001). More specifically, carriers of the long allele exhibited a significantly higher magnitude of CPM(nonpainful) than carriers of the short allele. No associations were found between the dopamine-related genes and both types of pain modulation. These results highlight the importance of serotonin in endogenous analgesia. ⋯ This article presents an association between the serotonin transporter gene polymorphism (5-HTTLPR) and pain modulation derived by nonpainful conditioned pain modulation (CPM(nonpainful)), rather than painful conditioned pain modulation (CPM(painful)). These findings emphasize the complex role of serotonin in pain modulation, and highlight the importance of genetic studies in the understanding of interindividual differences in sensitivity to pain.
-
It is assumed that pain-related fear, a present response to an immediate danger or threat such as pain, plays a significant role in the experience of pediatric pain. However, there are no measures to adequately measure this construct in children and adolescents. The purpose of this study was to develop and test the psychometric properties of a scale to assess pain-related fear to be used with Catalan-speaking children and adolescents between 7- and 16-years-old. We initially developed a list of items that reflected the physiological, cognitive, and behavioral components of pain-related fear components. We also queried an international group of experts, and interviewed children and adolescents. After pilot testing the initial version with a sample of 10 children, we administered the questionnaire to a sample of schoolchildren (n = 273) and children from medical clinics (n = 164) through individual interviews. Additional information was also collected during the interview to study the psychometric properties of the scale. Ten days after the initial interview, participating schoolchildren were requested to answer the questionnaire again. Item analysis and exploratory factor analysis with data from the school sample produced 2 meaningful factors (namely, Fearful thoughts and Fearful physical feelings and behaviors). Findings also showed that the Pediatric Pain Fear Scale (total scale and the 2 subscales) was both reliable and valid. This scale could help researchers to gain a better understanding about the role of pain-related fear in children and adolescents and support clinical decision-making. ⋯ This article presents a new measure of fear associated with pain in children and adolescents. This measure could potentially help researchers to gain a better understanding about the role of pain-related fear in children and adolescents and support clinical decision-making.
-
A burgeoning body of evidence supports the efficacy and elucidates the mechanisms of placebo analgesia. Debate persists, however, concerning their ethical use, with many of the present arguments being philosophically based. The present web-based study empirically investigated the acceptability of an analgesic placebo treatment. Participants (103) responded to vignettes depicting patients receiving a placebo analgesic. We experimentally manipulated: 1) placebo treatment instructions (level of deception); 2) treatment outcome; and 3) patients' pain severity. Participants rated vignettes on outcome measures of deception, physician-patient relationship, and patient mood. Participants then characterized a range of placebo acceptability through ratings of deceptiveness, effectiveness, and negative consequences. Results showed that placebos described as "medication shown to be a powerful analgesic in some people" were equally deceptive as those described as "standard drug treatment." Ratings of patient mood and physician approval were determined as much by treatment instruction as by treatment outcome and an analgesic response mitigated the negative consequences of deceptive administration. Participants tolerated moderate effectiveness and considerable negative consequences in an acceptable placebo, although results suggest lay individuals may not have a sophisticated conceptualization of placebo effectiveness. Studies altering individuals' understanding of placebo effectiveness and mechanisms are needed to identify additional factors determining placebo acceptability. ⋯ This study represents an empirical examination of analgesic placebo acceptability among lay individuals. This article is the first to systematically manipulate deception, treatment outcome, and disease severity to determine how these factors interact to differentially determine placebo acceptability-a highly relevant finding that informs the clinical use of placebo.