The journal of pain : official journal of the American Pain Society
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Self-reported pain intensity assessments are central to chronic pain research. Ecological momentary assessment (EMA) methodologies are uniquely positioned to collect these data, and are indeed being used in the field. However, EMA protocols are complex, and many decisions are necessary in the design of EMA research studies. A systematic literature review identified 105 articles drawing from 62 quantitative EMA research projects examining pain intensity in adult chronic pain patients. Study characteristics were tabulated to summarize and describe the use of EMA, with an emphasis placed on various dimensions of decision-making involved in executing EMA methodologies. Most identified studies considered within-person relationships between pain and other variables, and a few examined interventions on chronic pain. There was a trend toward the use of smartphones as EMA data collection devices more recently, and completion rates were not reported in nearly one third of studies. Pain intensity items varied widely with respect to number of scale points, anchor labels, and length of reporting period; most used numeric rating scales. Recommendations are provided for reporting to improve reproducibility, comparability, and interpretation of results, and for opportunities to clarify the importance of design decisions. ⋯ Studies that use EMA methodologies to assess pain intensity are heterogeneous. Aspects of protocol design, including data input modality and pain item construction, have the potential to influence the data collected. Thorough reporting on design features and completion rates therefore facilitates reproducibility, comparability, and interpretation of study results.
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The polytrauma clinical triad refers to the co-occurrence of chronic pain, traumatic brain injury (TBI), and posttraumatic stress disorder (PTSD). Despite research implicating dyadic relationships between these conditions and adverse outcomes, scant research has examined the polytrauma clinical triad's relation to suicide or violence. The present cross-sectional study was designed to examine whether this complex clinical presentation increases risk of suicidal ideation and violent impulses after accounting for other established risk factors. Veterans who served in the military since September 11, 2001 (N = 667) who reported chronic pain completed an interview and self-report battery. Bivariate analyses showed that suicidal ideation and violent impulses both correlated with PTSD, TBI+PTSD, pain intensity and interference, drug abuse, and major depressive disorder (MDD). Multiple regression analyses showed that: 1) race, chronic pain with PTSD, alcohol abuse, and MDD significantly predicted suicidal ideation, 2) pain interference, chronic pain with TBI, chronic pain with PTSD, chronic pain with TBI+PTSD, drug abuse, and MDD significantly predicted violent impulses, and 3) pain interference was a more critical predictor of suicidal and violent ideation than pain intensity. Implications for risk assessment and treatment are discussed. ⋯ This article presents results from a study examining predictors of suicide and violence risk among a sample of post-9/11 U.S. Veterans with chronic pain. Health care professionals should assess for pain interference, TBI, PTSD, depression, and alcohol/drug abuse when conducting risk assessments with this population.
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Clinical Trial
Transcranial Alternating Current Stimulation at Alpha Frequency Reduces Pain When the Intensity of Pain is Uncertain.
Alpha activity directly before pain onset has been implicated in pain experience with higher prestimulus alpha associated with lower reported pain. However, expectations about pain intensity also seem to affect prestimulus alpha activity. To date, evidence for a relationship between alpha activity and pain experience has been largely correlational. ⋯ Visual cues preceding the pain stimulus were used to manipulate uncertainty. A significant tACS × Uncertainty × Stimulus intensity interaction was found for reported pain intensity (F2,44 = 4.50, P = .017, partial η2 = .17) and unpleasantness (F1,22 = 4.78, P = .040, partial η2 = .18). Pain experience during the application of somatosensory alpha tACS was significantly lowered compared with sham stimulation, but only when the intensity of an upcoming stimulus was uncertain.
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Although the clinical application of opioids for pain management is often hindered by undesired behavioral impairment, preclinical assays of antinociception typically do not provide information regarding the behaviorally disruptive effects of opioids that may accompany their antinociceptive effects. To address this, we modified a warm water tail withdrawal procedure to determine concurrently the effects of opioids on tail withdrawal latency (antinociception) and indices of food-maintained operant behavior (rates of responding and reinforcement density) in squirrel monkeys. Six opioid agonists were tested, and all produced dose-dependent antinociception and impairment of operant behavior. ⋯ Oxycodone, heroin, buprenorphine, and methadone all produced similar ED50 ratios (.82-1.14), whereas butorphanol yielded a significantly lower ED50 ratio (.17) reflecting behavioral disruption at doses producing only minimal antinociception. The antinociceptive and behaviorally disruptive effects of oxycodone and buprenorphine were further characterized using Schild analysis to calculate apparent pA2 values for antagonism of the 2 drugs by naltrexone. These analyses suggest that µ-receptor mechanisms likely mediate the antinociceptive as well as behaviorally disruptive effects of oxycodone (pA2 values: 8.13 and 8.57) and buprenorphine (pA2 values: 8.6 and 7.9).
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Experimental pain research frequently relies on the recruitment of volunteers. However, because experimental pain research often involves unpleasant and painful sensations, it may be especially susceptible to sampling bias. That is, volunteers in experimental pain research might differ from nonvolunteers on several relevant variables that could affect the generalizability and external validity of the research. ⋯ Study 1 showed that lower levels of fear of pain, higher levels of sensation-seeking, and older age predicted the perceived likelihood of participating in pain research. Study 2 showed significantly higher levels of sensation-seeking in participants who signed up for the pain study compared with those who signed up for the no-pain study. The implications of these findings for future research, as well as the clinical conclusions on the basis of experimental pain research, are discussed.