title: Intratesticular lidocaine reduces the response to surgical castration in dogs.
abstract: OBJECTIVE
  To investigate whether intratesticular injection of lidocaine pre-surgery would reduce the intraoperative responses to elective castration in dogs.
  
  
  METHODS
  Double-blinded, randomized, controlled, prospective clinical study.
  
  
  METHODS
  Forty-two client-owned dogs weighing 2.2-38.4 kg and aged between 4.5 and 56 months.
  
  
  METHODS
  Group L dogs received an intratesticular injection of 2% lidocaine (2 mg kg(-1)) and Group S an identical volume of saline prior to surgery. Premedication was with acepromazine and morphine intramuscularly. Anaesthesia was induced with propofol intravenously and maintained with isoflurane vaporized in oxygen. Heart rate (HR), mean arterial pressure (MAP), respiratory rate (f(R)), end-tidal isoflurane (Fe'ISO) and carbon dioxide concentrations, oxygen saturation and ECG were monitored during surgery. Fe'ISO was maintained at 1.0±0.1%. Supplemental propofol was given in response to gross movement.
  
  
  RESULTS
  Group L had significantly lower maximum values for both HR and MAP. Group L displayed significantly smaller increases in HR during exteriorization of the first testis than Group S. There was an overall significant difference in MAP between groups during all surgical events (p=0.041) and time points (p=0.002). In univariate analysis, Group L showed significantly less changes in MAP during skin incision, exteriorization of the first testis and clamping of both spermatic cords. Group S reached its highest f(R) significantly earlier. Group L (eight dogs) required additional propofol 33±18 minutes after the start of surgery and Group S (seven dogs) at 19±17 minutes; this difference was not statistically significant. Seven dogs in Group L and 12 dogs in Group S required rescue analgesia with morphine (GCMPS-SF score ≥6); this difference was not statistically significant. No adverse effects were reported postoperatively.
  
  
  CONCLUSIONS
  Based on this study, the authors recommend the use of intratesticular lidocaine for surgical castration in dogs.
authors.affiliation: UCD Veterinary Hospital, School of Veterinary Medicine, University College Dublin, Dublin, Ireland. vilhelmiina.huuskonen@ucd.ie
authors.forename: Vilhelmiina
authors.initials: V
authors.lastname: Huuskonen
authors.forename: J M Lynne
authors.initials: JM
authors.lastname: Hughes
authors.forename: Elisa
authors.initials: E
authors.lastname: Estaca Bañon
authors.forename: Eleanor
authors.initials: E
authors.lastname: West
mesh_terms: D000768:Anesthesia, General / Q000662:veterinary; D000779:Anesthetics, Local / Q000008:administration & dosage; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004285:Dogs; D006339:Heart Rate / Q000187:drug effects; D007267:Injections / Q000662:veterinary; D007432:Intraoperative Period; D008012:Lidocaine / Q000008:administration & dosage; D008297:Male; D009919:Orchiectomy / Q000379:methods / Q000662:veterinary*; D013737:Testis / Q000187:drug effects
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine