**4.2 Postoperative pain control and acute pain service reality**

Postoperative pain is usually a multifactorial acute-on-chronic pain caused by the surgical procedure and the preexisting disease. It is triggered by the response to the trauma of the tissues caused by the surgical act. The control of the postoperative pain is a cornerstone in the postoperative setting and the access to palliative care and pain therapy should be granted. Failure to control postoperative pain has repercussions on the entire system from the patient, by worsening his experience and memories of the already traumatic event, to the hospital structure, by prolonging length of stay, and to the healthcare system, by increasing costs [95]. The postoperative pain therapy should include a preventive approach starting from aiming to a surgical procedure as less invasive as possible such as in case of hip replacement, anterior surgical approach, or robotic surgery [96]. In addition, the so-called preemptive analgesia aims to reduce the initial acute response to pain preventing, or at least limiting, the neuronal modifications associated with windup that consist in a progressively increasing electrical response in the corresponding spinal cord (posterior horn) neurons by repeated stimulation of group C peripheral nerve fibers. Multimodal approach is another preventive technique, with the choice of drugs belonging to different analgesic classes and using techniques of locoregional anesthesia, optimizing analgesia, and minimizing side effects. Similarly, to the anesthesia approach, the pain management after hip replacement should be multimodal, and it must be monitored and managed by an acute pain service (APS). There are different possibilities for postoperative pain control in hip replacement: totally intravenous analgesic infusion, continuous and/or patient-controlled peridural analgesia, and continuous or patient-controlled perineural analgesia; since the first experience of treatment units for acute pain management [97], the benefits of a dedicated and multidisciplinary organization have been reported and accepted, also in terms of cost-effectiveness [98, 99]. Unfortunately, the correct management of postoperative pain is still a challenge in most realities, and APSs are not yet enough diffused. It is possible to differentiate two main APS models: the first is the US model, which consists of anesthesiologist-based comprehensive pain management teams; the second is a nurse-based supervised APS, more diffused

#### *Anesthesia for Hip Replacement DOI: http://dx.doi.org/10.5772/intechopen.104666*

in the European countries. A recent Italian study suggests that the creation of the APS model, managed by residents in anesthesia, may represent an alternative between the US model (expensive and difficult to apply in several healthcare systems) and a nurse-based model more frequent in European countries [95].
