European journal of pain : EJP
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Randomized Controlled Trial
Rewarded placebo analgesia: A new mechanism of placebo effects based on operant conditioning.
Placebo analgesia is explained by two learning processes: classical conditioning and observational learning. A third learning process, operant conditioning, has not previously been investigated as a mechanism of placebo effects. We aimed to induce placebo analgesia by operant conditioning. ⋯ According to the current placebo literature, placebo analgesia can be explained by two learning processes: classical conditioning and observational learning. A third learning process, operant conditioning, has not previously been investigated as a mechanism of placebo effects. Our study reveals that patients can learn placebo analgesia as a result of operant conditioning, suggesting that randomized controlled trials could be improved by controlling the reinforcement that might occur spontaneously when patients interact with, for example, medical personnel.
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Pain models are commonly used in drug development to demonstrate analgesic activity in healthy subjects and should therefore not cause long-term adverse effects. The ultraviolet B (UVB) model is a model for inflammatory pain in which three times the minimal erythema dose (3MED) is typically applied to induce sensitization. Based on reports of long-lasting postinflammatory hyperpigmentation (PIH) associated with 3MED, it was decided to investigate the prevalence of PIH among subjects who were previously exposed to 3MED at our research centre. In addition, re-evaluation of the UVB inflammation model using a reduced exposure paradigm (2MED) was performed in healthy subjects. ⋯ Postinflammatory hyperpigmentation is an unwanted long-term side effect associated with the UVB inflammation model using the 3× minimal erythema dose (3MED) paradigm. In contrast, using a 2MED paradigm results in hyperalgesia that is stable for 36 hr and has a lower risk of inducing postinflammatory hyperpigmentation.
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It would be desirable to identify patients with acute low back pain (ALBP) who are at high risk for transition to chronic pain early in the course of their disease. This would enable early preventive or therapeutic interventions. Patients with chronic low back pain (CLBP) display signs of central hypersensitivity. This may contribute to the transition to CLBP. We tested the hypothesis that central hypersensitivity as assessed by quantitative sensory tests predicts transition to CLBP. ⋯ We found no evidence to support a clinically relevant ability of current quantitative sensory tests to predict the transition from acute to CLBP.
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Long-term opioid prescribing for musculoskeletal pain is controversial due to uncertainty regarding effectiveness and safety. This study examined the risks of a range of adverse events in a large cohort of patients prescribed long-term opioids using the UK Clinical Practice Research Datalink. ⋯ Long-term opioid use is associated with serious adverse events such as major trauma, addiction and overdose. The risk increases with higher opioid doses. Opioid prescribing should be reviewed before long-term use becomes established, and periodically thereafter to assess ongoing effectiveness.
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Estimation of a patient's pain may have a considerable impact on the level of care that patient receives. Many studies have shown that contextual factors may influence an observer's pain estimation. Here, we investigate the effect of an observer's impression of a person in pain and justification of his/her pain on the observer's pain estimation, tendency to help and perceived empathy. ⋯ Observers' estimation of pain, perceived empathy and tendency to help biases by their understanding of the characteristics of the person in pain. In clinical settings, these biases may influence the quality of care and well-being of patients. Understanding the underlying mechanisms of these biases can help us improve the quality of care and control the effect of prejudices on pain assessment.