Pain
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Neuropathic pain (NP) in cancer patients lacks standards for diagnosis. This study is aimed at reaching consensus on the application of the International Association for the Study of Pain (IASP) special interest group for neuropathic pain (NeuPSIG) criteria to the diagnosis of NP in cancer patients and on the relevance of patient-reported outcome (PRO) descriptors for the screening of NP in this population. An international group of 42 experts was invited to participate in a consensus process through a modified 2-round Internet-based Delphi survey. ⋯ Agreement was also reached on clinical examination by soft brush or pin stimulation (MEDs⩾7 and IQRs⩽3) and on the use of PRO descriptors for NP screening (MED=8, IQR=3). Based on the study results, a clinical algorithm for NP diagnostic criteria in cancer patients with pain was proposed. Clinical research on PRO in the screening phase and on the application of the algorithm will be needed to examine their effectiveness in classifying NP in cancer patients.
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Research on placebo analgesia and nocebo hyperalgesia has primarily included healthy subjects or acute pain patients, and it is unknown whether these effects can be obtained in ongoing pain in patients with chronic pain caused by an identifiable nerve injury. Eighteen patients with postthoracotomy neuropathic pain were exposed to placebo and nocebo manipulations, in which they received open and hidden administrations of pain-relieving (lidocaine) or pain-inducing (capsaicin) treatment controlled for the natural history of pain. Immediately after the open administration, patients rated their expected pain levels on a mechanical visual analogue scale (M-VAS). ⋯ Pain increases during nocebo were nonsignificant (P=.394 to 1.000). To our knowledge, this is the first study to demonstrate placebo effects in ongoing neuropathic pain. It provides further evidence for placebo-induced reduction in hyperalgesia and suggests that patients' expectations coexist with emotional feelings about treatments.
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Activity pacing is a widely used self-management strategy, but we lack a clear understanding of its nature and usefulness. One source of confusion is a lack of clarity about the use of pacing in everyday life (ie, naturalistic pacing) in people not trained on how to pace activities. It is unknown whether people engage in more pacing when pain is high (pain-contingent) or when fatigue is high (fatigue-contingent). ⋯ Contrary to our hypothesis, increased pacing was associated with higher subsequent levels of pain and fatigue. Naturalistic pacing seems symptom-contingent and not reinforced by symptom reduction. Naturalistic pacing may be distinct from trained or programmatic pacing in terms of outcomes, and further research into naturalistic pacing may provide an important foundation for how best to deliver activity pacing interventions.
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Placebo effects can act as powerful pain relievers. Although the ethics of therapeutic placebo use are highly controversial, recent evidence suggests that medical providers frequently utilize placebo treatments and patients may be open to these interventions in certain contexts. This investigation used a patient-centered approach to answer essential questions about placebo treatment acceptability. ⋯ Also, an analgesic placebo response mitigated the negative consequences of deception by improving provider trust and decreasing negative mood. These findings suggest that, contrary to popular belief, patients may be rather pragmatic in their appraisals of placebo treatment acceptability, and may consider a variety of treatments/contexts as ethically permissible for managing their pain. This is the first study of its kind to quantify perceptions of placebo analgesia knowledge and efficacy among individuals with chronic pain, and to assess the role of different medical contexts in treatment acceptability.
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Detection of external irritants by head nociceptor neurons has deep evolutionary roots. Irritant-induced aversive behavior is a popular pain model in laboratory animals. It is used widely in the formalin model, where formaldehyde is injected into the rodent paw, eliciting quantifiable nocifensive behavior that has a direct, tissue-injury-evoked phase, and a subsequent tonic phase caused by neural maladaptation. ⋯ Using TRPA1-blocker and Trpa1(-/-) mice, we found that both TRP channels co-contribute to the formalin trigeminal pain response. These results imply TRPV4 as an important signaling molecule in irritation-evoked trigeminal pain. TRPV4-antagonistic therapies can therefore be envisioned as novel analgesics, possibly for specific targeting of trigeminal pain disorders, such as migraine, headaches, temporomandibular joint, facial, and dental pain, and irritation of trigeminally innervated surface epithelia.