Articles: hyperalgesia.
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Central sensitisation is associated with chronic pain in whiplash patients. Predicting which patients will develop central sensitisation is difficult but patient expectations of recovery predict a variety of outcomes in whiplash patients. ⋯ Whiplash patients who expect 'never to get better' or 'don't know' have a much higher likelihood of developing at least one sign of central sensitisation 3 months after their collision.
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Burn injury induces severe pain that can be refractory to existing pharmacotherapies. The underlying mechanism of burn pain remains unclear. We previously established an animal model and reported that unilateral burn injury induces chronic and bilateral mechanical allodynia, which is associated with central sensitization and microglial activation in the spinal cord dorsal horn. Modulation of the activity of microglia and p38 mitogen-activated protein kinase (MAPK) has been shown to ameliorate neuropathic pain in several nerve-injury pain models. In the present study, we show in this rat model that daily treatment with the microglial inhibitor minocycline (10 mg/kg), administered at the time of burn injury and for 7 days thereafter, significantly attenuates ipsilateral and contralateral allodynia as assessed up to 1 month following burn injury. These sensory changes are paralleled by significant suppression of evoked hyperexcitability of dorsal-horn neurons and of the expression of phosphorylated p38 (phospho-p38) in OX42+ microglial cells within the dorsal horn. Our results suggest that modulation of inflammation at early times after burn injury may have long-lasting effects, attenuating central neuropathic mechanisms which contribute to pain after burn injury. ⋯ We demonstrate, in a rodent model of burn-associated pain, that the microglial inhibitor minocycline, delivered at the time of burn injury and for 1 week thereafter, has long-lasting effects, attenuating microglial activation and neuronal hyperresponsiveness in the dorsal horns, and ameliorating allodynia for at least 1 month.
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Celecoxib is a non-steroidal anti-inflammatory drug (NSAID) that selectively inhibits cyclooxygenase-2 (COX-2). Like most NSAIDs, celecoxib exhibits analgesic effects in models of inflammatory pain but these appear to be dependent on endogenous opioid release. Therefore, this study has assessed the ability of celecoxib to induce tolerance in rats, comparable to that induced by morphine. ⋯ Naltrexone prevented induction of tolerance to morphine or celecoxib. The present results strengthen the possibility that celecoxib has also mechanisms of analgesia unrelated to COX inhibition but dependent on endogenous opioid release. Our results also imply the existence of a new class of analgesics without the deleterious effects of COX inhibitors.
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Treatment with opioid medications has grown over the past decades, but has been surrounded by some ongoing controversy and debate to whether it is causing more harm than good for patients. To this end, the field of pain management has suffered from a lack of clarity about some basic definitions on concepts such as tolerance and hyperalgesia. Some characterize these issues as inevitable parts of opioid therapy while other schools of thought look at these issues as relatively rare occurrences. ⋯ Looking at the pattern of medication usage change over time, 34.5 percent experienced dose stabilization after the initial titration, 13.2 percent had early dose stabilization within one dose change, and an additional 14.7 percent actually had dose decreases after surgeries or other interventional procedures. Only 6.6 percent of the sample had to be discharged or weaned from controlled substances over time in the clinic. Thus, it appears that tolerance and hyperalgesia are not foregone conclusions when considering placing a patient on long-term opioid therapy.
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Randomized Controlled Trial Comparative Study
Maintenance anaesthetics during remifentanil-based anaesthesia might affect postoperative pain control after breast cancer surgery.
Although remifentanil provides profound analgesia during operation, postoperative occurrence of hyperalgesia and tolerance after remifentanil administration could be a challenge to the postoperative pain control. In this investigation, we sought to determine the effect of maintenance with propofol or sevoflurane on postoperative analgesia after remifentanil-based anaesthesia. ⋯ Remifentanil hyperalgesia was induced by high dose of remifentanil-based anaesthesia during sevoflurane anaesthesia, whereas that was not apparent during propofol anaesthesia. Also, remifentanil hyperalgesia did not occur during low dose of remifentanil-based anaesthesia. Maintenance of propofol during high-dose remifentanil-based anaesthesia provided better postoperative analgesia.