The journal of pain : official journal of the American Pain Society
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Effective relief of acute and long-term postoperative pain is of utmost importance to patients undergoing surgery. Here, we worked on a controlled procedure of abdominal surgery in the rat inducing persistent postoperative pain symptoms for up to 10 days and tested the efficacy of perioperative care with the local anesthetic ropivacaine. Laparotomy was likewise used to implant radiotelemetric probes by which electrocardiogram, body temperature, and locomotor activity were recorded in freely moving animals. We showed that postoperative pain symptoms (mechanical allodynia) measured in periphery of the scar were associated over time with persistent tachycardia, elevated heart rate variability, and loss of mobility. Furthermore, a single subcutaneous infiltration of the local anesthetic ropivacaine in the periphery of the abdominal incision was sufficient to prevent the appearance of allodynia and the associated cardiac and motor signs of pain, monitored by radiotelemetry. These beneficial effects were observed when the infiltration was performed in the perioperative period, but not later. This study on freely moving animals exhibiting long-lasting postoperative pain symptoms and altered autonomic/motor function illustrates well the importance of the timing of preemptive analgesia care with long-acting local anesthetics. Moreover, it emphasizes the utility of monitoring heart rate variability to quantify spontaneous expression of long-lasting postoperative pain. ⋯ Speeding the recovery time after surgery using perioperative ropivacaine care is of significant clinical relevance because it might limit the risk of chronic pain and postoperative complications. In humans, chronobiological analysis of heart rate variability could also help quantify spontaneous pain expression with minimal emotional bias.
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Although direct experience and verbal instruction are important sources in the development of pain-related beliefs and behaviors, accumulating evidence indicates that observation of others in pain may be equally as important. Taking a contemporary view on learning as a starting point, we discuss available evidence on observational learning in the context of pain, highlight its importance for both development and management of chronic pain problems, and discuss potential moderators of observational learning effects. We argue that the capacity to understand and appreciate the experience of another person is fundamental to observational learning, including use of this information to establish the association between pain and antecedent or consequent stimuli. A main objective of this paper is to stimulate research on the role of learning about pain from others. Several lines for further research, including clinical applications, are delineated. ⋯ Based upon a contemporary view on learning, this focus article delineates how pain-related beliefs and behaviors may be learnt by observing others. It is discussed how further research on the acquisition of pain-related beliefs/behaviors might further our understanding of pain and disability.
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Chronic pain is a debilitating clinical condition associated with a variety of disease entities including diabetic neuropathy, postherpetic neuralgia, low back pathology, fibromyalgia, and neurological disorders. For many general practitioners and specialists, managing chronic pain has become a daunting challenge. As a modality of multidisciplinary chronic pain management, medications are often prescribed in combinations, an approach referred to as combination drug therapy (CDT). However, many medications for pain therapy, including antidepressants and opioid analgesics, have significant side effects that can compound when used in combination and impact the effectiveness of CDT. To date, clinical practice of CDT for chronic pain has been based largely on clinical experiences. In this article, we will focus on (1) the scientific basis and rationales for CDT, (2) current clinical data on CDT, and (3) the need for more clinical studies to establish a framework for the use of CDT. ⋯ More preclinical, clinical, and translational studies are needed to improve the efficacy of combination drug therapy that is an integral part of a comprehensive approach to the management of chronic pain.
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Western studies document the prevalence of chronic pain in the general adult population to be between 2 and 55%. Knowing the prevalence of chronic pain among Chinese populations provides important comparative perspective: To determine the prevalence of chronic pain in the general population of Hong Kong; evaluate the relationship of chronic pain with sociodemographic and lifestyle factors; and describe the pain characteristics among chronic pain sufferers. A total of 5,001 adults aged ≥ 18 years (response rate 58%) drawn from the general population of Hong Kong completed the Chronic Pain Grade (CPG) questionnaire, providing information on chronic pain and sociodemographic status using telephone interviews. Overall 34.9% reported pain lasting more than 3 months (chronic pain), having an average of 1.5 pain sites; 35.2% experienced multiple pain sites, most commonly of the legs, back, and head with leg and back being rated as the most significant pain areas among those with multiple pain problems. The CPG criteria classified 21.5% of those with chronic pain symptoms as Grade III or above. Fully adjusted stepwise regression analyses identified being female, older age, divorced/separated, having part-time employment, existing long-term health problems, higher HADS Anxiety scores, poor QoL (mental health component), and low self-perceived health to be significantly associated with chronic pain. ⋯ Our data evidenced that chronic pain is common in the general population of Hong Kong, and the prevalence is highest among women and middle-aged adults.
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Randomized Controlled Trial
The endogenous opioid system is not involved in modulation of opioid-induced hyperalgesia.
Some recent studies suggested a role of the endogenous opioid system in modulating opioid-induced hyperalgesia (OIH). In order to test this hypothesis, we conducted a prospective randomized, placebo-controlled, 2-way crossover study in healthy human volunteers. We utilized a well-established model of inducing OIH after a brief exposure to the μ-opioid agonist remifentanil using intradermal electrical stimulation. Patients were exposed to a randomized 90-minute infusion of remifentanil or saline placebo during 2 separate occasions. Development of OIH was quantified using changes in the average radius of the area of secondary hyperalgesia generated by electrical pain stimulation. A 23.6% (20.2) increase in area of secondary hyperalgesia over baseline was observed in the postinfusion period of the remifentanil session, demonstrating development of OIH (P = .03). In order to test endogenous opioid system modulation of OIH, patients were given a 1-time bolus of naloxone, which had no effect on the size of the hyperalgesic lesion in either the remifentinal or placebo session. These results suggested that the endogenous opioid system did not appear to modulate OIH. ⋯ Experimental evidence suggested that the endogenous opioid system did not significantly affect opioid-induced hyperalgesia. Consequently, this study suggested that alternative mechanisms such as pronociceptive stimulation and neuroplastic changes might be responsible for expression of OIH.