title: Effect of perioperative perineural injection of dexamethasone and bupivacaine on a rat spared nerve injury model.
abstract: BACKGROUND
  Neuropathic pain resulting from diverse causes is a chronic condition for which effective treatment is lacking. The goal of this study was to test whether dexamethasone exerts a preemptive analgesic effect with bupivacaine when injected perineurally in the spared nerve injury model.
  
  
  METHODS
  Fifty rats were randomly divided into five groups. Group 1 (control) was ligated but received no drugs. Group 2 was perineurally infiltrated (tibial and common peroneal nerves) with 0.4% bupivacaine (0.2 ml) and dexamethasone (0.8 mg) 10 minutes before surgery. Group 3 was infiltrated with 0.4% bupivacaine (0.2 ml) and dexamethasone (0.8 mg) after surgery. Group 4 was infiltrated with normal saline (0.2 ml) and dexamethasone (0.8 mg) 10 minutes before surgery. Group 5 was infiltrated with only 0.4% bupivacaine (0.2 ml) before surgery. Rat paw withdrawal thresholds were measured using the von Frey hair test before surgery as a baseline measurement and on postoperative days 3, 6, 9, 12, 15, 18 and 21.
  
  
  RESULTS
  In the group injected preoperatively with dexamethasone and bupivacaine, mechanical allodynia did not develop and mechanical threshold forces were significantly different compared with other groups, especially between postoperative days 3 and 9 (P < 0.05).
  
  
  CONCLUSIONS
  In conclusion, preoperative infiltration of both dexamethasone and bupivacaine showed a significantly better analgesic effect than did infiltration of bupivacaine or dexamethasone alone in the spared nerve injury model, especially early on after surgery.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jeong Beom
authors.initials: JB
authors.lastname: Lee
authors.forename: Seong Soo
authors.initials: SS
authors.lastname: Choi
authors.forename: Eun Hye
authors.initials: EH
authors.lastname: Ahn
authors.forename: Kyung Don
authors.initials: KD
authors.lastname: Hahm
authors.forename: Jeong Hun
authors.initials: JH
authors.lastname: Suh
authors.forename: Jung Gil
authors.initials: JG
authors.lastname: Leem
authors.forename: Jin Woo
authors.initials: JW
authors.lastname: Shin