title: Cardiopulmonary effects and anaesthesia recovery quality in horses anaesthetized with isoflurane and low-dose S-ketamine or medetomidine infusions.
abstract: OBJECTIVE
  To evaluate cardiopulmonary effects and anaesthesia recovery quality in horses anaesthetized with isoflurane receiving medetomidine or S-ketamine infusions.
  
  
  METHODS
  Randomized, blinded, prospective clinical trial.
  
  
  METHODS
  Fifty horses undergoing elective surgery.
  
  
  METHODS
  After acepromazine and flunixin meglumine premedication, horses received medetomidine (7 μg kg-1) intravenously (IV). Anaesthesia was induced with midazolam and racemic ketamine (Med treatment group; 2.2 mg kg-1; n = 25) or S-ketamine (S-ket treatment group; 1.1 mg kg-1; n = 25) IV and maintained with isoflurane in oxygen/air and medetomidine (Med; 3.5 μg kg-1hour-1) or S-ketamine (S-ket; 0.5 mg kg-1hour-1). All horses were mechanically ventilated. Cardiopulmonary variables were evaluated. Isoflurane end-tidal concentrations (Fe'Iso), dobutamine requirements and thiopental boli were recorded. Plasma samples were collected in six horses to evaluate S-ketamine and S-norketamine concentrations. After surgery, medetomidine 2 μg kg-1was administered IV. Four independent observers scored recovery using a visual analogue scale and a numerical rating scale.
  
  
  RESULTS
  Both groups required similar mean Fe'Iso (1%). However, S-ket horses needed more thiopental boli. Median intraoperative cardiac index values were higher with S-ket (4.5 L minute-1m-2) than Med (3.9 L minute-1m-2). Overall, there were no differences in heart rate, blood pressure or dobutamine requirements; however, horses in S-ket showed higher heart rate values at 30 minutes after anaesthesia induction. Compared with Med horses, S-ket horses showed decreased PaO2and increased pulmonary venous admixture values estimated with the Fshunt calculation. Recoveries were shorter and of poorer quality with S-ket. During infusion, S-ketamine and S-norketamine plasma concentrations lay in the ranges of 0.209-0.917 μg mL-1and 0.250-0.723 μg mL-1, respectively.
  
  
  CONCLUSIONS
  Despite the higher intraoperative cardiac index with S-ket, both protocols were considered to provide acceptable cardiovascular function. However, recovery quality was significantly better in the Med group.
authors.affiliation: Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: M Paula Larenza
authors.initials: MP
authors.lastname: Menzies
authors.affiliation: Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: Simone K
authors.initials: SK
authors.lastname: Ringer
authors.affiliation: Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: Aude
authors.initials: A
authors.lastname: Conrot
authors.affiliation: Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Berne, Berne, Switzerland.
authors.forename: Regula
authors.initials: R
authors.lastname: Theurillat
authors.affiliation: Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: Katharina
authors.initials: K
authors.lastname: Kluge
authors.affiliation: Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: Annette Pn
authors.initials: AP
authors.lastname: Kutter
authors.affiliation: Clinic for Equine Surgery, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: Michelle
authors.initials: M
authors.lastname: Jackson
authors.affiliation: Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Berne, Berne, Switzerland.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Thormann
authors.affiliation: Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland. regula.bettschart-wolfensberger@uzh.ch.
authors.forename: Regula
authors.initials: R
authors.lastname: Bettschart-Wolfensberger
mesh_terms: D000762:Anesthesia Recovery Period; D000771:Anesthesia, Intravenous / Q000662:veterinary*; D019162:Anesthetics, Combined; D000818:Animals; D002319:Cardiovascular System / Q000187:drug effects; D005260:Female; D006736:Horses / Q000601:surgery*; D007530:Isoflurane / Q000008:administration & dosage; D007649:Ketamine / Q000008:administration & dosage; D008297:Male; D020926:Medetomidine / Q000008:administration & dosage; D011446:Prospective Studies; D012119:Respiration / Q000187:drug effects; D016037:Single-Blind Method
chemical_list: D019162:Anesthetics, Combined; D007649:Ketamine; D007530:Isoflurane; D020926:Medetomidine
keywords: S-ketamine; S-norketamine; anaesthesia; horse; isoflurane; medetomidine