Pathophysiology of acute postoperative pain and scientific rationale of

Background: The dentoalveolar surgery, in particular the extraction of mandibular impacted third molars, is the most commonly performed one in Oro-Maxillo-Facial surgery. As demonstrated by clinical experience, this type of intervention can be affected by a series of post-operative sequelae, and Acute Postoperative Pain (APP) is the less tolerated one by the patient. In recent decades, the practical need to minimize the pain that follow an extraction, together with improved understanding of the pathophysiological mechanisms of pain, led to the research of new analgesic techniques. An improvement was the idea to "prevent the pain development rather than treating it post-operatively", this innovation led us to develop the technique known as "Pre-Emptive Analgesia" (preventive analgesia). Despite the promising results obtained with “Pre-Emptive Analgesia” experimental models, clinical results are not unambiguous. Objectives: The objective of this study is to describe the rational basis of “Pre-Emptive Analgesia” technique and its controversies presented in literature concerning this analgesic method. Methods: The method consisted in a careful analysis of the pathophysiological mechanisms underlying the acute post-operative pain in order to explain the scientific rationale of “Pre-Emptive Analgesia”. Results: Despite the “Pre-Emptive Analgesia” has been amply demonstrated in experimental models, its practical application is still very much debated. The conflict subjects are the proper name and the definition of “Pre-Emptive Analgesia”, as well as the drug choice that is used for the pre-emptive treatment and its treatment regimen (route of administration, timing, dose, dosage and duration of treatment). Another problem concerning the “Pre-Emptive Analgesia” is that the most of clinical studies concern major surgery in which painful stimuli differ widely in terms of intensity and duration to those obtained in ambulatory surgery with local anaesthetics. It is also demonstrated that “Pre-Emptive Analgesia” effectiveness is influenced by the type of surgery performed. Moreover, considering the fact that the acute post-operative pain, being a multidimensional experience, is linked to psychological factors that influence the results obtained with the “Pre-Emptive Analgesia”. Discussion and Conclusions: The concept of "Pre-Emptive Analgesia" evolved in the course of time until it was definitively given the correct rational basis on which it is based, but unfortunately it still remains a very controversial topic. Despite that, the clinicians’ confidence about the