Transitional pain and the risk factors for CPSP: novel targets for CPSP preventive strategies?Pain, specifically chronic pain, is highly complex, combining sensory and emotional dimensions as well as psychosocial aspects. The presence of a neuropathic component is frequently incriminated in severe CPSP. 18 The negative impact of these neuropathic symptoms on recovery makes accurate diagnosis and treatment mandatory. Various therapeutic strategies both patient and symptoms specific are available. Some treatments e.g. capsaicin application seem to show better results with earlier application (within 6 months of diagnosis). It is here worth noting that neuropathic component in postoperative pain may develop as early as 48h after surgery with a high predictive value of persistence at 2 months and later. 19 In other cases, neuropathic component may develop later after a free interval as demonstrated after various surgical procedures including thoracic surgery. The later finding underlines the importance of patient's followup. Neuropathic symptoms and pain have a negative impact on function. 18 In orthopedic surgery mainly hip and knee arthroplasties, several publications have defined a critical phase in the recovery process i.e. the first 2 to 3 months at the end of which patients with poor outcome should be identified and require more intensive clinical care. 8,20 Pain catastrophizing and number of painful body regions have been associated with poor pain and functional outcome trajectories after knee arthroplasty. 20 Both pharmacologic and non-pharmacologic treatments might be appropriate to help those patients. The control of opioid analgesics intake as aforementioned is also mandatory. 21 Finally, after hospital discharge, the psychosocial dimension of pain may increase in relation to the influence of familial and environmental factors. 15 The management of family behaviors and cognitions may be sometimes necessary to improve the efficacy of patient's treatment. In example, parental pain catastrophizing significantly affects child recovery trajectory after major surgical procedure whereas the child catastrophizing does not. 15 Conclusion Chronic postsurgical pain is now recognized as an important individual and socio-economic factor which may be difficult to relieve. A remained unchanged incidence over the past decades points out the failures of perioperative preventive strategies. Because pain is a dynamic process, current researches now focuse on the progression from acute to chronic pain to better understand associative and causal risk factors. Consequently, the subacute pain period also called transitional pain is now a novel target to apply preventive treatments and to try to reduce the development of CPSP. For that reason, the concept of 'transitional pain services' stands a corner stone of perioperative medicine. 22 Abstracts A42