title: Effects of high and low inspired fractions of oxygen on horse erythrocyte membrane properties, blood viscosity and muscle oxygenation during anaesthesia.
abstract: OBJECTIVE
  To evaluate whether a period of hyperoxia or after a period of hypoxia produced changes attributable to reactive oxygen species in anaesthetized horses.
  
  
  METHODS
  Prospective randomized experimental study.
  
  
  METHODS
  Six healthy (ASA I) geldings, aged 4.5-9.5 years and weighing 510-640 kg(-1).
  
  
  METHODS
  After 30 minutes breathing air as carrier gas for isoflurane, horses were assigned randomly to breathe air as carrier gas (CG0.21) or oxygen as carrier gas (CG1.00) for a further 90 minutes. After an interval of 1 month each horse was re-anaesthetized with the other carrier gas for the 90 minute test period. Ventilation was controlled throughout anaesthesia. Arterial blood was sampled to measure gas tensions, lactate, cholesterol, vitamin E, 4-hydroxy-alkenals, 8-epi-PGF(2 alpha), half haemolysis time, half erythrolysis time, and erythrocyte membrane fluidity. Muscle blood flow and oxygenation were evaluated by near infrared spectroscopy and coloured Doppler.
  
  
  RESULTS
  After the first 30 minutes horses were hypoxemic. Subsequently the CG1.00 group became hyperoxaemic (PaO(2) approximately 240 mmHg) whereas the CG0.21 group remained hypoxaemic (PaO(2) approximately 60 mmHg) and had increased lactate concentration. No significant changes in vitamin E, 4-hydroxy-alkenals, or 8-epi-PGF(2 alpha) concentrations were detected. During the 90 minute test period the CG0.21 group had increased resistance to free-radical-mediated lysis in erythrocytes, whereas the CG1.00 group had slightly decreased resistance of whole blood to haemolysis. CG0.21 induced a progressive muscle deoxygenation whereas CG1.00 induced an increase in muscle oxygen saturation followed by progressive deoxygenation towards baseline.
  
  
  CONCLUSIONS
  and clinical relevance During isoflurane anaesthesia in horses, the hyperoxia induced by changing from air to oxygen induced minimal damage from reactive oxygen species. Using air as the carrier gas decreased skeletal muscle oxygenation compared with using oxygen.
authors.affiliation: Ecole Nationale Vétérinaire de Lyon, Equine Department, Université de Lyon, Lyon, France. k.portier@vet-lyon.fr
authors.forename: Karine
authors.initials: K
authors.lastname: Portier
authors.forename: David
authors.initials: D
authors.lastname: Crouzier
authors.forename: Michel
authors.initials: M
authors.lastname: Guichardant
authors.forename: Michel
authors.initials: M
authors.lastname: Prost
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Debouzy
authors.forename: Nathalie
authors.initials: N
authors.lastname: Kirschvink
authors.forename: Nicole
authors.initials: N
authors.lastname: Fellmann
authors.forename: Pierre
authors.initials: P
authors.lastname: Lekeux
authors.forename: Jean
authors.initials: J
authors.lastname: Coudert
mesh_terms: D000768:Anesthesia, General / Q000662:veterinary; D000818:Animals; D001809:Blood Viscosity / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects; D004912:Erythrocytes / Q000502:physiology*; D006736:Horses / Q000097:blood / Q000502:physiology*; D015227:Lipid Peroxidation; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000502:physiology*; D017382:Reactive Oxygen Species; D014810:Vitamin E / Q000097:blood
chemical_list: D017382:Reactive Oxygen Species; D014810:Vitamin E; D010100:Oxygen