Non-opioid Analgesic Combination With Morphine for Postoperative Analgesia.

Since the description of the concept of balanced analgesia in the early 90's, the combination of different analgesic drugs and/or analgesia techniques is part of the standard management of postoperative analgesia. A recent survey conducted in France by Fletcher et al. showed that patients often received one or more NOA associated with an opioid. The benefit and risk of the use of opioids associated with NOA were recently reassessed as part of a formal recommendation of experts and detailed in a recent review. The analysis of the literature reveals a lack of comparison of the combinations of NOA with morphine for postoperative analgesia. For example, paracetamol and morphine in combination does not always allow a significant morphine-sparing effect compared with morphine alone and does not reduce the incidence of morphine side effects. A number of definitive answers has therefore yet to be found: Does NOA -morphine association allow an effective morphine-sparing effect? Is there an interest in prescribing several NOAs in association? If yes, what are the most interesting combinations in terms of morphine-sparing effect and safety? Another question concerns the effects of NOA on postoperative hyperalgesia. This hyperalgesia, which results from surgery-related inflammation, is increased by consumption of morphine and not only contributes to the overall experience of postoperative pain but also to the chronicisation of postoperative pain. Since in clinical practice, hyperalgesia can be measured using specific tools (Von Frey filament type), our study will evaluate the anti-hyperalgesic effects of NOA on a subgroup of patients enrolled in the centers used to evaluate nociceptive thresholds. The objectives of this study are : * comparing the morphine sparing effect of different combination of 3 NOA (paracetamol, nefopam, ketoprofen) for postoperative analgesia. * determining whether the morphine-sparing effect is associated with or without a reduction in the incidence of morphine side effects. * evaluating the effects of NOA on postoperative hyperalgesia.