Articles: hyperalgesia.
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Curr Opin Anaesthesiol · Oct 2013
ReviewMechanisms of regional anaesthesia protection against hyperalgesia and pain chronicization.
The aim of the present review is to describe how regional anaesthesia might oppose neuronal changes that surgery and opioids cause in the central nervous system to block both pain sensitization and chronicization following surgery. This might help anaesthesiologists to better understand the impact of their practice on the development of postoperative chronic pain. ⋯ Regional anaesthesia is able to reduce postoperative acute hyperalgesia and long-term chronic pain by decreasing pain sensitization induced by the surgery itself, and intraoperative use and opioid-induced hyperalgesia. Nevertheless, clinical studies on neuraxial anaesthesia and nerve blocks did not bring so far a strong conclusion to this question, and further better designed studies are necessary.
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Nature reviews. Neurology · Oct 2013
ReviewReappraising neuropathic pain in humans--how symptoms help disclose mechanisms.
Neuropathic pain--that is, pain arising directly from a lesion or disease that affects the somatosensory system--is a common clinical problem, and typically causes patients intense distress. Patients with neuropathic pain have sensory abnormalities on clinical examination and experience pain of diverse types, some spontaneous and others provoked. Spontaneous pain typically manifests as ongoing burning pain or paroxysmal electric shock-like sensations. ⋯ Paroxysmal sensations can be caused by several mechanisms; for example, electric shock-like sensations probably arise from high-frequency bursts generated in demyelinated non-nociceptive Aβ fibres. Most human and animal findings suggest that brush-evoked allodynia originates from Aβ fibres projecting onto previously sensitized nociceptive neurons in the dorsal horn, with additional contributions from plastic changes in the brainstem and thalamus. Here, we propose that the emerging mechanism-based approach to the study of neuropathic pain might aid the tailoring of therapy to the individual patient, and could be useful for drug development.
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There is a curious and paradoxic phenomenon, reliably demonstrated in animal models, that consists of an increased sensitivity to pain that is apparently induced by the very opioid drugs used to ameliorate the pain. This phenomenon is termed "opioid-induced hyperalgesia." Whether opioid-induced hyperalgesia occurs in humans, and, if so, to what extent and consequence, is far less established. This is a critical question for attempting to treat pain. ⋯ It would be to decrease, rather than increase, the dose of opioid. We review the evidence, particularly the clinical evidence, about opioid-induced hyperalgesia and the postulated mechanisms. We conclude that given the clinical ramifications, opioid-induced hyperalgesia is one of the most understudied important aspects of opioid research.
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Paediatric anaesthesia · Aug 2013
ReviewLow-dose ketamine as a potential adjuvant therapy for painful vaso-occlusive crises in sickle cell disease.
The hallmark of sickle cell disease (SCD) is the acute painful vaso-occlusive crisis (VOC). Among SCD patients, vaso-occlusive pain episodes vary in frequency and severity. Some patients rarely have painful crises, while others are admitted to the hospital multiple times in a year for parenteral analgesics. ⋯ Low-dose ketamine, by virtue of its NMDA receptor agonist activity, could be a useful adjuvant to opioid therapy in patients with refractory SCD-related pain. Based on limited studies of adjuvant ketamine use for pain management, low-dose ketamine continuous infusion appears safe. Further clinical investigations are warranted to fully support the use of low-dose ketamine infusion in patients with SCD-related pain.
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The phenomena of habituation and sensitization are considered most useful for studying the neuronal substrates of information processing in the CNS. Both were studied in primary headaches, that are functional disorders of the brain characterized by an abnormal responsivity to any kind of incoming innocuous or painful stimuli and it's cycling pattern over time (interictal, pre-ictal, ictal). The present review summarizes available data on stimulus responsivity in primary headaches obtained with clinical neurophysiology. ⋯ Generalized increased sensitivity to pain (lower thresholds and increased pain rating) and a dysfunction in supraspinal descending pain control systems may contribute to the development and/or maintenance of central sensitization in chronic TTH. Cluster headache patients are characterized during the bout and on the headache side by a pronounced lack of habituation of the brainstem blink reflex and a general sensitization of pain processing. A better insight into the nature of these ictal/interictal electrophysiological dysfunctions in primary headaches paves the way for novel therapeutic targets and may allow a better understanding of the mode of action of available therapies.