title: Anaesthetic potency of isoflurane in cattle: determination of the minimum alveolar concentration.
abstract: OBJECTIVE
  To determine the minimum alveolar concentration (MAC) of isoflurane in cattle.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  Sixteen healthy adult female Holstein-Friesian cattle weighing 612 ± 17 kg (× ± SEM) and aged 5.7 ± 0.9 years old.
  
  
  METHODS
  The unsedated cattle were restrained in right lateral recumbency using a rope harness technique. Anaesthesia was induced with isoflurane (ISO) in oxygen via a face mask connected to a large-animal, semiclosed anaesthetic circle system. Each cow was intubated with a cuffed orotracheal tube (25 mm ID). Inspired and end-tidal ISO were monitored using a calibrated infra red analyser with a methane filter. The MAC of ISO that prevented gross purposeful movement in response to a tail and dewclaw clamp was determined. The time from the start of ISO administration to intubation, the time interval between discontinuance of ISO and the time the animal regained sternal recumbency, were recorded. Time to standing and quality of recovery were also recorded.
  
  
  RESULTS
  The time from the start of ISO administration to tracheal intubation was 18.68 ± 2.77 minutes. The MAC of ISO in these cattle was 1.27 ± 0.03% (1.14 ± 0.01% corrected to sea level). Time to sternal recumbency after 90 ± 16 minutes of anaesthesia from intubation was 4.60 ± 0.58 minutes and time to standing was 6.70 ± 1.02 minutes. All cattle were extubated when they regained sternal recumbency.
  
  
  CONCLUSIONS
  The MAC of isoflurane in these cattle was 1.27 ± 0.03% (1.14 ± 0.01% corrected to sea level). ISO provided a smooth induction to, and rapid recovery from, anaesthesia.
  
  
  CONCLUSIONS
  Knowledge of the MAC of ISO in cattle will facilitate its appropriate clinical use.
authors.affiliation: Hospital Clínico Veterinario Rof Codina, Facultad de Veterinaria de Lugo, Universidad de Santiago de Compostela, Spain.
authors.forename: A G
authors.initials: AG
authors.lastname: Cantalapiedra
authors.affiliation: Hospital Clínico Veterinario Rof Codina, Facultad de Veterinaria de Lugo, Universidad de Santiago de Compostela, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Villanueva
authors.affiliation: Hospital Clínico Veterinario Rof Codina, Facultad de Veterinaria de Lugo, Universidad de Santiago de Compostela, Spain.
authors.forename: J L
authors.initials: JL
authors.lastname: Pereira
keywords: Cattle; hypercapnia; inhalant anaesthesia; isoflurane; minimum alveolar concentration (MAC)