European journal of pain : EJP
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Intramuscular injections of hypertonic saline are commonly used to induce experimental muscle pain, but reliability data on this technique are lacking. This study investigated the intra- and interindividual reliability of pain measures from a hypertonic saline injection into the vastus lateralis. ⋯ Many pain research studies have performed intramuscular injections of hypertonic saline to investigate responses to muscle pain. However, the reliability of this technique is not well established. We examined the pain response over three repeated sessions of a hypertonic saline injection. The pain induced by hypertonic saline has considerable interindividual variability but has largely acceptable intraindividual reliability. Therefore, the injections of hypertonic saline to induce muscle pain are a reliable model of experimental muscle pain.
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A critical aspect for most human pain research is the ability of participants to communicate their first-person, experiential perspective to a third-person observer. This communication is frequently accomplished via pain ratings. The scale type can influence the communication of pain experiences and can contribute to gender differences in pain. This study examined the role of gender on pain ratings using noxious and innocuous stimuli across two types of rating scales. ⋯ There are differences in the usage of rating scales in which ratings for auditory, visual and noxious somatosensory stimuli are higher with NRS compared to VAS. Choosing a rating scale for research or clinical use should take this different item functioning into account.
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Chronic pain of different aetiologies and localization has been associated with less grey matter volume (GMV) in several cortical and subcortical brain areas. Recent meta-analyses reported low reproducibility of GMV alterations between studies and pain syndromes. ⋯ Grey matter reorganization could serve as a diagnostic biomarker for chronic pain. In a large cohort, we here replicated findings of less grey matter volume across three pain conditions in the left anterior and posterior insula, anterior cingulate and left hippocampus. Less hippocampal grey matter was mediated by experienced stress.
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Infrared laser stimulation is a valuable tool in pain research, its primary application being the recording of laser-evoked brain potentials (LEPs). Different types of laser stimulators, varying in their skin penetrance, are likely to have a large influence on the LEPs, when stimulating different skin types. The aim of this study was to investigate how LEPs depend on laser type and skin location. ⋯ This study showed that the elicitation of laser-evoked potentials in healthy humans greatly depends on the combination of laser stimulator type and skin type. It was shown that high penetrance laser stimuli are capable of eliciting responses in both hairy and glabrous skin, whereas low penetrance stimuli barely elicited responses from the glabrous skin. Computational modelling was used to demonstrate that the results could be fully explained by the combination of laser type and skin thickness.
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Pain empathy is essential for high-quality of care. The cognitive ability to identify and understand the pain in others remains underexplored in the context of hospital shift work. This study aimed to observe the early subliminal ability to detect pain in other faces and to investigate pain intensity evaluations during day and night shifts. ⋯ Some professions need to know how to assess pain 24/7 and a lack of sleep can disrupt the cognitive processes necessary for this assessment. Night shifts provoke a bias in pain management, and sleep deprivation, a decrease in pain evaluation. By conducting a repeated measure study in the field that applied a different paradigm (subliminal recognition of facial cues) we add evidence to the understanding of pain recognition and the impact of sleep deprivation on the early processing of pain in others.