The use of intraoperative epidural or spinal analgesia modulates postoperative hyperalgesia and reduces residual pain after major abdominal surgery

Introduction : The use of intraoperative multimodal analgesia has clearly improved postoperative pain control, mortality and morbidity after major surgical procedures. However, very few clinical trials have studied the longterm impact of intraoperative epidural or spinal analgesia on chronic postsurgical pain (CPSP) development. Even less studies have evaluated the modulatory effect of intraoperative neuraxial analgesia on objective changes (i.e. mechanical hyperalgesia) reflecting central sensitization. Methods : The present work compares general anesthesia alone (GA group) versus general anesthesia combined to either intraoperative epidural analgesia (EPID group : combination of bupicavaine, sufentanil and clonidine 1 mu g/kg) or spinal analgesia (IT group : either bupivacaine or clonidine 300 mu g) on the development of secondary mechanical hyperalgesia and the incidence of CPSP after major abdominal surgery. Data analyzed in the present work involve adult patients undergoing surgical resection of rectal adenocarcinoma who participated in three previously published randomized trials. Results : Intraoperative epidural and particularly spinal analgesia reduced both incidence (p < 0.05 between GA alone and spinal analgesia) and extent (area) of secondary mechanical hyperalgesia surrounding the wound at 48h and 72 h after surgery. The use of intraoperative epidural and spinal analgesia also reduced CPSP incidence. Postoperative area of mechanical hyperalgesia seems positively correlated with the incidence CPSP. Conclusion : An effective intraoperative neuraxial block of nociceptive inputs from the wound using multimodal analgesia - specifically when involving spinal analgesics and antihyperalgesic drugs - contributes to prevent central sensitization and hence reduces CPSP after major abdominal procedures.