title: Alfaxalone compared with ketamine for induction of anaesthesia in horses following xylazine and guaifenesin.
abstract: OBJECTIVE
  To compare anaesthesia induced with either alfaxalone or ketamine in horses following premedication with xylazine and guaifenesin.
  
  
  METHODS
  Randomized blinded cross-over experimental study.
  
  
  METHODS
  Six adult horses, five Standardbreds and one Thoroughbred; two mares and four geldings.
  
  
  METHODS
  Each horse received, on separate occasions, induction of anaesthesia with either ketamine 2.2 mg kg(-1) or alfaxalone 1 mg kg(-1) . Premedication was with xylazine 0.5 mg kg(-1) and guaifenesin 35 mg kg(-1) . Incidence of tremors/shaking after induction, recovery and ataxia on recovery were scored. Time to recovery was recorded. Partial pressure of arterial blood oxygen (PaO(2) ) and carbon dioxide (PaO(2) ), arterial blood pressures, heart rate (HR) and respiratory rates were recorded before premedication and at intervals during anaesthesia. Data were analyzed using Wilcoxon matched pairs signed rank test and are expressed as median (range).
  
  
  RESULTS
  There was no difference in the quality of recovery or in ataxia scores. Horses receiving alfaxalone exhibited a higher incidence of tremors/shaking on induction compared with those receiving ketamine (five and one of six horses respectively). Horses recovered to standing similarly [28 (24-47) minutes for alfaxalone; 22 (18-35) for ketamine] but took longer to recover adequately to return to the paddock after alfaxalone [44 (38-67) minutes] compared with ketamine [35 (30-47)]. There was no statistical difference between treatments in effect on HR, PaO(2) or PaCO(2) although for both regimens, PaO(2) decreased with respect to before premedication values. There was no difference between treatments in effect on blood pressure.
  
  
  CONCLUSIONS
  Both alfaxalone and ketamine were effective at inducing anaesthesia, although at induction there were more muscle tremors after alfaxalone. As there were no differences between treatments in relation to cardiopulmonary responses or quality of recovery, and only minor differences in recovery times, both agents appear suitable for this purpose following the premedication regimen used in this study.
authors: School of Veterinary Science, The University of Queensland, Gatton Campus, Qld, Australia. h.keates@uq.edu.au
authors: Helen L
authors: HL
authors: Keates
authors: Andrew W
authors: AW
authors: van Eps
authors: Martin R B
authors: MR
authors: Pearson
mesh_terms: D000762:Anesthesia Recovery Period; D000771:Anesthesia, Intravenous / Q000662:veterinary; D000778:Anesthetics, Dissociative / Q000494:pharmacology; D018686:Anesthetics, Intravenous / Q000494:pharmacology; D000818:Animals; D018592:Cross-Over Studies; D005260:Female; D006140:Guaifenesin / Q000008:administration & dosage / Q000494:pharmacology*; D006736:Horses; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000494:pharmacology; D007649:Ketamine / Q000494:pharmacology*; D008297:Male; D011277:Pregnanediones / Q000494:pharmacology*; D013997:Time Factors; D014991:Xylazine / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000778:Anesthetics, Dissociative; D018686:Anesthetics, Intravenous; D006993:Hypnotics and Sedatives; D011277:Pregnanediones; D014991:Xylazine; D006140:Guaifenesin; D007649:Ketamine; C006477:alphaxalone