Is opioid-induced hyperalgesia a genuine issue for palliative care patients and clinicans?

Abstract

197 Background: Opioid-Induced Hyperalgesia (OIH) has been described as a paradoxical response whereby opioid administration induces an increase in pain sensitivity rather than an analgesic effect. It is proposed this results from increased pro-nociceptive sensitivity following changes in central and peripheral neural pathways. While there is basic science and pre-clinical evidence supporting OIH, debate remains about its clinical relevance or even existence. The existence or otherwise of OIH has relevance for palliative care as many patients are prescribed opioids and the standard management of unstable pain in palliative care may worsen symptoms in OIH. Therefore recognition of the concept would seem important for palliative care clinicians. Methods: An electronic survey of Australian and New Zealand palliative care clinicians was undertaken addressing awareness of OIH as well as approaches to recognising and managing it. The survey which contained single response, multiple-choice and open-ended questions was distributed through the Australian New Zealand Society of Palliative Medicine. Mixed-methods analysis was performed. Results: One hundred and twenty-three surveys were returned (response rate = 31%). The majority of respondents identified as palliative care specialists. More than 75% of respondents reported observing OIH in their clinical practice, often with malignant disease and with morphine, oxycodone and fentanyl identified as the commonest causal agents. The three features felt to be most suggestive of OIH were; escalating pain despite increasing opioids, demonstrable hyperalgesia or allodynia and a more diffuse pain distribution away from pre-existing pain sites. Most clinicians utilized more than one approach when OIH was encountered. The commonest of these were opioid reduction, opioid rotation and optimization of adjuvant analgesia. Conclusions: Our survey found a higher rate of reported observation of OIH amongst clinicians than might have been anticipated given debate about the existence of OIH in humans outside of a research environment. These results suggest that many palliative care clinicians perceive OIH to be a genuine issue for their patients.