title: Effect of inhalation of isoflurane at end-tidal concentrations greater than, equal to, and less than the minimum anesthetic concentration on bispectral index in chickens.
abstract: OBJECTIVE
  To determine the effect of inhalation of isoflurane at end-tidal concentrations greater than, equal to, and less than the minimum anesthetic concentration (MAC) on bispectral index (BIS) in chickens. Animals-10 chickens.
  
  
  METHODS
  For each chicken, the individual MAC of isoflurane was determined by use of the toe-pinch method. After a 1-week interval, chickens were anesthetized with isoflurane at concentrations 1.75, 1.50, 1.25, 1.00, and 0.75 times their individual MAC (administered from higher to lower concentrations). At each MAC multiple, a toe pinch was performed and BIS was assessed and correlated with heart rate, blood pressure, and an awareness score (derived by use of a visual analogue scale).
  
  
  RESULTS
  Among the chickens, mean +/- SD MAC of isoflurane was 1.15 +/- 0.20%. Burst suppression was detected at every MAC multiple. The BIS and awareness score were correlated directly with each other and changed inversely with increasing isoflurane concentration. Median (range) BIS values during anesthesia at 1.75, 1.50, 1.25, 1.00, and 0.75 MAC of isoflurane were 25 (15 to 35), 35 (25 to 45), 35 (20 to 50), 40 (25 to 55), and 50 (35 to 65), respectively. Median BIS value at extubation was 70 +/- 9. Values of BIS correlated with blood pressure, but not with heart rate. Blood pressure changed with end-tidal isoflurane concentrations, whereas heart rate did not.
  
  
  CONCLUSIONS
  Assessment of BIS can be used to monitor the electrical activity of the brain and the degree of unconsciousness in chickens during isoflurane anesthesia.
authors.affiliation: Clinic of Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Winterthurerstr 260, 8057 Switzerland.
authors.forename: Olga
authors.initials: O
authors.lastname: Martin-Jurado
authors.forename: Rainer
authors.initials: R
authors.lastname: Vogt
authors.forename: Annette P N
authors.initials: AP
authors.lastname: Kutter
authors.forename: Regula
authors.initials: R
authors.lastname: Bettschart-Wolfensberger
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Hatt
mesh_terms: D000280:Administration, Inhalation; D000758:Anesthesia / Q000379:methods; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D002645:Chickens / Q000502:physiology*; D005260:Female; D007530:Isoflurane / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008991:Monitoring, Physiologic; D010100:Oxygen / Q000097:blood
chemical_list: D018685:Anesthetics, Inhalation; D002245:Carbon Dioxide; D007530:Isoflurane; D010100:Oxygen