title: Attenuation of pain in a randomized trial by suppression of peripheral nociceptive activity in the immediate postoperative period.
abstract: Peripheral neuronal barrage from tissue injury produces central nervous system changes that contribute to the maintenance of postoperative pain. The therapeutic approaches to blocking these central changes remain controversial, because previous studies have not differentiated presurgical interventions from those administered after tissue injury, yet before pain onset. In this study, we evaluated the relative contributions of blockade of nociceptive input during surgery or during the immediate postoperative period on pain suppression. Subjects were randomly allocated to one of four groups: preoperative 2% lidocaine, postoperative 0.5% bupivacaine, both, or placebo injections. General anesthesia was induced and third molars extracted. Pain was assessed over 4 h and at 24 and 48 h. The beta-endorphin in blood samples increased twofold during surgery, which is indicative of activation of the peripheral nociceptive barrage in response to painful stimuli. Pain was decreased in the immediate postoperative period in the bupivacaine groups, whereas it increased in the lidocaine group over time. Pain intensity was less 48 h after surgery in the groups whose postoperative pain was blocked by the administration of bupivacaine, but no effect was demonstrated for the preoperative administration of lidocaine alone. These results in the oral surgery pain model suggest that minimizing the peripheral nociceptive barrage during the immediate postoperative period decreases pain at later time periods. In contrast, blocking the intraoperative nociceptive barrage does not appear to contribute significantly to the subsequent reduction in pain.
  
  
  CONCLUSIONS
  Suppression of postoperative pain immediately after surgery attenuates the pain experienced 1 to 2 days after surgery. These findings suggest that pain after minor surgery can be prevented by blocking the development of pain processes that amplify pain for days after surgery.
authors.affiliation: National Institute of Dental and Craniofacial Research/NIH, 19 Center Drive, Room 1N-117, Bethesda, MD 20892, USA.
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Gordon
authors.forename: Jaime S
authors.initials: JS
authors.lastname: Brahim
authors.forename: Ronald
authors.initials: R
authors.lastname: Dubner
authors.forename: Linda M
authors.initials: LM
authors.lastname: McCullagh
authors.forename: Christine
authors.initials: C
authors.lastname: Sang
authors.forename: Raymond A
authors.initials: RA
authors.lastname: Dionne
mesh_terms: D000082:Acetaminophen / Q000008:administration & dosage / Q000627:therapeutic use; D000328:Adult; D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage / Q000627:therapeutic use; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000627:therapeutic use; D000768:Anesthesia, General; D000772:Anesthesia, Local; D003061:Codeine / Q000008:administration & dosage / Q000627:therapeutic use; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D009619:Nociceptors / Q000187:drug effects*; D010147:Pain Measurement; D010149:Postoperative Pain / Q000188:drug therapy*; D017933:Peripheral Nervous System / Q000187:drug effects*; D011795:Surveys and Questionnaires; D001615:beta-Endorphin / Q000097:blood
chemical_list: D018712:Analgesics, Non-Narcotic; D000701:Analgesics, Opioid; D000082:Acetaminophen; D001615:beta-Endorphin; D003061:Codeine