Opioid-induced hyperalgesia : a pathological or physiological phenomenon ? Study development of an animal model of acute hyperalgesia to sufentanil under general anesthesia

Opioids are the most frequently used drugs to relieve moderate to severe pain. In addition to their analgesic effects, opioids induce dependence and tolerance. These phenomena are well-known in the setting of chronic pain therapy. Nevertheless, opioids can unexpectedly enhance pain and extend pain states even after a single administration. This condition, termed hyperalgesia, is defined as an increased sensitivity to noxious stimuli.Because, in daily clinical practice, opioids are frequently used for balanced anesthesia and postoperative pain management, the experimentally proved hyperalgesic effect of opioids leads clinicians and researchers to question how drugs recognized to alleviate pain, may have the opposite effect. In other words, in anesthetic setting, do the opioids enhance pain or promote postsurgical pain? The present work will focus on the intriguing concept of opioid-induced hyperalgesia (OIH). Its originality is the development of a new animal model where the paradoxical effect of opioids is expressed under general anesthesia, mimicking clinical practice. From the investigations, it appears that OIH may occur after the administration of a very low dose of sufentanil under volatile anesthesia. The mechanisms underlying this paradoxical effect in anesthetized animals are similar to those implicated in OIH after high doses of opioids in awake animals. Moreover, this pro-nociceptive effect disappears in co-existing chronic pain presuming common underlying mechanisms with injury-induced hyperalgesia. This work might be considered as a supplemental investigation of the paradoxical phenomenon of OIH in the perioperative context. Anesthesia is more than simply a loss of consciousness. Anesthetic management may have an impact on postoperative pain and perioperative management should be individualized to each patient.(SBIM 3) -- UCL, 201