title: Circulatory, respiratory and behavioral responses in isoflurane anesthetized llamas.
abstract: OBJECTIVE
  To evaluate the circulatory, respiratory and behavioral effects of isoflurane (ISO) anesthesia in llamas during mechanical ventilation and spontaneous breathing.
  
  
  METHODS
  Prospective randomised study.
  
  
  METHODS
  Six adult, neutered male llamas (10 ± 1 years [mean ± SD], 179 ± 32 kg).
  
  
  METHODS
  Animals in which the minimum alveolar concentration (MAC) had been previously determined were anesthetized with ISO in oxygen. Inspired and end-tidal (ET) ISO were sampled continuously. Arterial blood pH, respiratory and circulatory variables, and clinical signs of anesthesia were recorded at three doses (1.0, 1.5 and 2.0 times the individual animal's MAC; mean MAC value 1.13%) of ISO during spontaneous and controlled ventilation. A series of Latin squares was used to determine order of dose. Controlled ventilation (CV) (target PaCO238 ± 5 mm Hg [5.0 ± 0.6 kPa]) preceded spontaneous ventilation (SV) at each dose. Animals breathed spontaneously for approximately 10 minutes prior to data collection. Body temperature was maintained at 37 ± 0.6 °C. Circulatory and respiratory data were analysed with a mixed model, least squares analysis of variance, for repeated measures taken at equally spaced intervals. p < 0.05.
  
  
  RESULTS
  Dose and mode of ventilation had significant influences on measured variables. For example, heart rate increased as dose increased; 67 ± 14 beats minute-1at 1.0 MAC-CV versus 77 ± 6 beats minute-1at 2 MAC-CV. Conversely, mean arterial pressure decreased with increasing dose; 82 ± 13 mm Hg at MAC-CV versus 52 ± 15 mm Hg at 2 MAC-CV. Arterial CO2increased with increasing dose during SV; 45 ± 5 mm Hg [6 ± 0.6 kPa] at MAC versus 53 ± 4 mmHg [7 ± 0.5 kPa] at 2 MAC. Reflex activity (e.g. palpebral reflex) and muscle tone (e.g. jaw tone) decreased while eyelid aperture increased with increasing anesthetic dose.
  
  
  CONCLUSIONS
  The influence of ISO dose and mode of ventilation on circulatory and respiratory variables in llamas is qualitatively similar to that reported in other species. Changes in reflex activity and muscle tone may be used to guide appropriate anesthetic delivery in ISO-induced llamas.
authors.affiliation: Department of Clinical Sciences, Colorado State University, Fort Collins, CO, USA.
authors.forename: Khursheed R
authors.initials: KR
authors.lastname: Mama
authors.affiliation: Department of Clinical Sciences, Colorado State University, Fort Collins, CO, USA.
authors.forename: Ann E
authors.initials: AE
authors.lastname: Wagner
authors.affiliation: Department of Surgical and Radiological Sciences, University of California-Davis, Davis, CA, USA.
authors.forename: Eugene P
authors.initials: EP
authors.lastname: Steffey
keywords: Anesthesia; circulatory; isoflurane; llama; respiratory