Abstract
BackgroundThe incidence of post-surgical chronic pain ranges between 20% and 40% in Europe. Osteoarthritis pain after prosthesis implantation is one of the most severe secondary syndromes, depending not only on surgery but also on organic changes before and after joints replacement. No data are available about risk factors. An excessive inflammatory response plays a central role but a best therapy is not defined yet. It is not clear whether opioid administration could influence post-surgical pain and lead to tolerance or addiction. Interestingly, the immune system, together with the nervous and peptidergic ones, is involved in hypersensibility. The connection across the three biological systems lies in the presence of opioid receptors on immune cells surface. Here, we show a method to analyze whether opioids could modulate lymphocytes, by proposing opioid receptors as biological markers to prevent chronic pain and opioid tolerance or addiction after hip surgery.Methods/designAfter institutional independent ethics committee approval, 60 patients, in pain and undergoing hip surgery, will be enrolled in a single-blind, randomized, phase IV, pilot study. Pain treatment will be selected inside a class of non-steroidal anti-inflammatory drugs (NAISDs) or paracetamol or a class of opioids, into three medication arms: 25 mg tapentadol twice daily; 75 mg tapentadol twice daily; NSAIDs or paracetamol in accordance with surgeon’s custom. For each group, we will collect blood samples before, during and after surgery, to apply molecular analysis. We will perform lymphocyte opioid receptors genes and proteins expression and functional analysis. Data will be statistically analyzed.DiscussionThis project has the potential to obtain a personalized diagnostic kit, by considering lymphocyte opioid receptors as biological markers. Starting from a simple blood sample, it will be possible to decide the best therapy for a single patient. Using a noninvasive approach, we expect to fix a daily standard dose and timing, before and after surgery, to bypass hip chronic pain and the insurgence of tolerance or addiction. The analysis of opioid receptors sensitivity will help to identify the best drug administration in each specific case (tailored therapy).Trial registrationISRCTN, ISRCTN12559751. Retrospectively registered on 23 May 2017.
Highlights
The incidence of post-surgical chronic pain ranges between 20% and 40% in Europe
Opioids are used in chronic pain therapy but the healing is overtaken by side effects, as well as respiratory and cognitive dysfunctions and immune impairment [20,21,22]
Opioid therapy is at the centre of a long debate because of its contrasting role in releasing pain and inducing, at the same time, tolerance and addiction [23]
Summary
The incidence of post-surgical chronic pain ranges between 20% and 40% in Europe. Osteoarthritis pain after prosthesis implantation is one of the most severe secondary syndromes, depending on surgery and on organic changes before and after joints replacement. An excessive inflammatory response plays a central role but a best therapy is not defined yet It is not clear whether opioid administration could influence post-surgical pain and lead to tolerance or addiction. Postoperative morbidity and persistent post-surgical pain is a complex unsolved problem, influencing patients’ outcomes and lives [1, 2] It has been called a silent epidemic of great social impact, by involving patients for more than 4 months after surgery [3]. The immune system is strictly linked to the nervous and peptidergic systems because of the presence of opioid receptors on the surfaces of blood cells [9], data are not available in relation to the insurgence of chronic pain. We show a study protocol to set up the best pre-surgery opioid dosage for an individual patient, through biological analysis of opioid receptors
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