Opioid-induced hyperalgesia: New insights into the chronicization of pain

The existence of opioid-induced hyperalgesia (OIH), ie, nociceptive sensitization, caused by exposure to opioids remains difficult to appraise in perioperative setting because objective assessment is rare, evidence mostly relying on subjective measures like pain scores and postoperative analgesics use. Basic diagnostic criteria of OIH are still needed. Experimental studies have highlighted the pronociceptive effects of intraoperative high doses of opioids in term of latent hypersensitivity and long-term vulnerability to pain. The real question in daily clinical practice is then whether OIH prevention matters and which patients might be concerned. Until recently, OIH has been associated to intraoperative administration of high doses of opioids, mainly remifentanil, which increases acute postoperative pain and perhaps might cause the persistence of postsurgical pain. Recently, the existence of preoperative OIH has been demonstrated in chronic pain patients under chronic opioids intake and its exacerbation by the administration of intraoperative opioids has been suggested. Finally, the effect of long-term postoperative opioids intake on pain persistence after surgery or trauma certainly deserves to be questioned. Thereby, the prevention of perioperative OIH should extend up to several weeks after surgery and should include chronic postsurgical pain. The later point argues for the development of dedicated chronic postsurgical pain services.