title: Influence of ketamine or xylazine supplementation on isoflurane anaesthetized horses--a controlled clinical trial.
abstract: OBJECTIVE
  To determine the influence of ketamine or xylazine constant rate infusions on isoflurane requirements, cardiovascular parameters and quality of anaesthesia in horses undergoing elective surgery.
  
  
  METHODS
  Prospective, matched paired clinical trial.
  
  
  METHODS
  Fifty four adult Warmblood horses.
  
  
  METHODS
  After premedication with acepromazine, xylazine and butorphanol, anaesthesia was induced with ketamine-midazolam and maintained with isoflurane alone (I), isoflurane with either 1 mg kg(-1)  hour(-1) ketamine (IK) or same dose of xylazine (IX). End tidal concentration of isoflurane (Fe'Iso) was adjusted by the same anaesthetist in all horses according to a scoring system. Dobutamine was infused to maintain mean arterial pressure (MAP) ≥70 mmHg. Arterial blood gases, heart rate (HR), respiratory rate, MAP and cardiac output (lithium dilution) were measured. Groups I and IK received xylazine before recovery. Recovery quality was scored.
  
  
  RESULTS
  Mean ± SD averaged Fe'Iso (volume%) was significantly lower in IX (0.95 ± 0.07) and IK (0.97 ± 0.08) than in I (1.16 ± 0.13). In group IX, HR was significantly lower and averaged MAP (90 ± 13 mmHg) significantly higher than in groups I (71 ± 7 mmHg) and IK (76 ± 7 mm Hg). Differences in other cardiopulmonary variables did not reach statistical significance. All horses recovered well with best score in group IX.
  
  
  CONCLUSIONS
  Both CRIs of xylazine and of ketamine resulted in pronounced reduction of isoflurane requirements and blood pressure support based on routinely monitored parameters. Cardiac output appeared well maintained in all three protocols, but lithium dilution induced errors mean the results are untrustworthy. The work requires repetition with another mode of measurement of cardiac output.
  
  
  CONCLUSIONS
  All three protocols provided good clinical anaesthesia with clinically acceptable cardiovascular effects.
authors.affiliation: Equine Clinic, University of Veterinary Medicine Hanover, Foundation, Hanover, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Pöppel
authors.forename: Klaus
authors.initials: K
authors.lastname: Hopster
authors.forename: Florian
authors.initials: F
authors.lastname: Geburek
authors.forename: Sabine
authors.initials: S
authors.lastname: Kästner
mesh_terms: D000700:Analgesics / Q000008:administration & dosage / Q000494:pharmacology*; D000762:Anesthesia Recovery Period; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000502:physiology*; D007530:Isoflurane / Q000008:administration & dosage / Q000494:pharmacology*; D007649:Ketamine / Q000008:administration & dosage / Q000494:pharmacology*; D014991:Xylazine / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000700:Analgesics; D018685:Anesthetics, Inhalation; D014991:Xylazine; D007649:Ketamine; D007530:Isoflurane
keywords: balanced anaesthesia; constant rate infusion; equine; ketamine; xylazine