British journal of anaesthesia
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Chronic pain is a state of physical suffering strongly associated with feelings of anxiety, depression and despair. Disease pathophysiology, psychological state, and social milieu can influence chronic pain, but can be difficult to diagnose based solely on clinical presentation. Here, we review brain neuroimaging research that is shaping our understanding of pain mechanisms, and consider how such knowledge might lead to useful diagnostic tools for the management of persistent pain in individual patients.
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Chronic pain is a public health concern affecting 20-30% of the population of Western countries. Although there have been many scientific advances in the understanding of the neurophysiology of pain, precisely assessing and diagnosing a patient's chronic pain problem is not straightforward or well-defined. How chronic pain is conceptualized influences how pain is evaluated and the factors considered when making a chronic pain diagnosis. ⋯ This evaluation should include a thorough patient history and medical evaluation and a brief screening interview where the patient's behaviour can be observed. Further assessment to address questions identified during the initial evaluation will guide decisions as to what additional assessments, if any, may be appropriate. Standardized self-reported instruments to evaluate the patient's pain intensity, functional abilities, beliefs and expectations, and emotional distress are available, and can be administered by the physician, or a referral for in depth evaluation can be made to assist in treatment planning.
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Research efforts over the past two decades have helped us better understand the biological mechanisms that lead to chronic pain. Despite this, there has been limited progress in developing novel analgesics to treat sufferers of persistent pain conditions, who may account for as many as one-fifth of the population. ⋯ We review the significant clinical evidence that neuronal activity from the periphery is a major contributor to painful symptom production and that peripheral mediators play a substantial role in this aberrant nociceptor activity. We discuss the clinical benefits of blocking individual known mediators and describe our own approach to identify novel mediators.
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The process of systematic review has shone a light on the methodology of randomized controlled trials. Notably, a range of potential biases hinders the interpretation of chronic pain trials. These include a consistent bias favouring active over placebo in trials that are small and of short duration. ⋯ They have been small and short, and used inappropriate imputation and outcomes unconnected to the experiences of most patients. While these designs are useful for answering some questions, they may be insensitive for many interventions. Newer designs, like enriched enrolment randomized withdrawal (EERW) trials or clinical effectiveness trials, are potentially more interesting and informative.