title: Behavioral responses following eight anesthetic induction protocols in horses.
abstract: OBJECTIVE
  To compare behavioral characteristics of induction and recovery in horses anesthetized with eight anesthetic drug protocols.
  
  
  METHODS
  Randomized prospective experimental study.
  
  
  METHODS
  Eight horses, 5.5 ± 2.4 years (mean ± SD) of age, and weighing 505 ± 31 kg.
  
  
  METHODS
  After xylazine pre-medication, each of eight horses was anesthetized on four occasions using one of eight different anesthetic induction protocols which incorporated various combinations of ketamine (KET), propofol (PRO), and thiopental (THIO): THIO 8 mg kg-1; THIO 6 mg kg-1+ PRO 0.5 mg kg-1; THIO 4 mg kg-1+ PRO 1 mg kg-1; THIO 2 mg kg-1+ PRO 1.5 mg kg-1; KET 2 mg kg-1; KET 1.5 mg kg-1+ PRO 0.5 mg kg-1; KET 1 mg kg-1+ PRO 1 mg kg-1; KET 0.5 mg kg-1+ PRO 1.5 mg kg-1. Quality of induction and recovery were scored from 1 (poor) to 5 (excellent), and time taken to achieve lateral recumbency, first movement, sternal recumbency, and standing were evaluated.
  
  
  RESULTS
  Time taken to achieve lateral recumbency after drug administration differed significantly (p < 0.0001) among the various combinations, being shortest in horses receiving THIO-8 (mean ± SD, 0.5 ± 0.3 minutes) and longest in horses receiving KET-2 (1.4 ± 0.2 minutes). The best scores for induction quality were associated with KET-1.5 + PRO-0.5, and the worst scores for induction quality were associated with KET-2, although the difference was not significant. Time to first movement varied significantly among drug protocols (p = 0.0133), being shortest in horses receiving KET-2 (12.7 ± 3.6 minutes) and longest in horses receiving THIO-8 (29.9 ± 1.5 minutes). Horses receiving THIO-8 made the greatest number of attempts to attain sternal posture (6.5 ± 4.7) and to stand (1.6 ± 0.8). Horses in the THIO-8 treatment also received the poorest recovery scores (3.3 ± 1.0 and 3.0 ± 0.7 for sternal and standing postures, respectively). The best recovery scores were associated with combinations comprised mainly of propofol.
  
  
  CONCLUSIONS
  Combining propofol with either ketamine or thiopental modifies behaviors associated with use of the individual drugs.
  
  
  CONCLUSIONS
  Quality of early anesthesia recovery in horses may be improved by some combinations of propofol with either thiopental or ketamine.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA. Electronic address: aewagner@lamar.colostate.edu.
authors.forename: Ann E
authors.initials: AE
authors.lastname: Wagner
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.
authors.forename: Khursheed R
authors.initials: KR
authors.lastname: Mama
authors.affiliation: Department of Surgical and Radiological Sciences (Steffey), School of Veterinary Medicine, University of California, Davis, CA, USA.
authors.forename: Eugene P
authors.initials: EP
authors.lastname: Steffey
authors.affiliation: Veterinary Teaching Hospital, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.
authors.forename: Lucien F
authors.initials: LF
authors.lastname: Brevard
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.
authors.forename: Peter W
authors.initials: PW
authors.lastname: Hellyer
keywords: anesthesia; equine; ketamine; propofol; recovery from anesthesia; thiopental