title: Clinical comparison of xylazine and medetomidine for premedication of horses.
abstract: OBJECTIVE
  To compare the analgesic and cardiopulmonary effects of medetomidine and xylazine when used for premedication of horses undergoing general anesthesia.
  
  
  METHODS
  Randomized clinical trial.
  
  
  METHODS
  40 horses.
  
  
  METHODS
  Twenty horses were premedicated with medetomidine (10 microg/kg [4.5 microg/lb], i.m.) and the other 20 were premedicated with xylazine (2 mg/kg [0.9 mg/kg], i.m.). Horses were then anesthetized with a combination of guaifenesin and ketamine; anesthesia was maintained with halothane. Additional doses of medetomidine or xylazine were given if horses were not sufficiently sedated at the time of anesthetic induction. After induction of anesthesia, sodium pentothal was administered as necessary to prevent limb movements. Hypotension was treated with dobutamine; hypoventilation and hypoxemia were treated with intermittent positive-pressure ventilation. The quality of anesthetic induction, maintenance, and recovery and the quality of the transition to inhalation anesthesia were scored.
  
  
  RESULTS
  Scores for the quality of the transition to inhalation anesthesia were significantly higher for horses premedicated with medetomidine than for horses premedicated with xylazine. However, other scores, recovery times, and numbers of attempts needed to achieve sternal recumbency and to stand were not significantly different between groups.
  
  
  CONCLUSIONS
  Results suggest that medetomidine is suitable for premedication of horses undergoing general anesthesia. Analgesic and cardiopulmonary effects of medetomidine were similar to those of xylazine, except that the transition to inhalation anesthesia was smoother when horses were premedicated with medetomidine, rather than xylazine.
authors.affiliation: Department of Veterinary Surgery 1, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido, Japan.
authors.forename: Kazuto
authors.initials: K
authors.lastname: Yamashita
authors.forename: William W
authors.initials: WW
authors.lastname: Muir
authors.forename: Sae
authors.initials: S
authors.lastname: Tsubakishita
authors.forename: Eric
authors.initials: E
authors.lastname: Abrahamsen
authors.forename: Phillip
authors.initials: P
authors.lastname: Lerch
authors.forename: John A E
authors.initials: JA
authors.lastname: Hubbell
authors.forename: Richard M
authors.initials: RM
authors.lastname: Bednarski
authors.forename: Roman T
authors.initials: RT
authors.lastname: Skarda
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Izumisawa
authors.forename: Tadao
authors.initials: T
authors.lastname: Kotani
mesh_terms: D000316:Adrenergic alpha-Agonists; D000768:Anesthesia, General / Q000662:veterinary; D000769:Anesthesia, Inhalation / Q000662:veterinary; D000771:Anesthesia, Intravenous / Q000662:veterinary; D000777:Anesthetics; D000818:Animals; D005260:Female; D006736:Horses / Q000502:physiology*; D006993:Hypnotics and Sedatives; D008297:Male; D020926:Medetomidine; D011229:Preanesthetic Medication / Q000662:veterinary*; D014991:Xylazine
chemical_list: D000316:Adrenergic alpha-Agonists; D000777:Anesthetics; D006993:Hypnotics and Sedatives; D014991:Xylazine; D020926:Medetomidine