Relationship of bispectral index to minimum alveolar concentration multiples of sevoflurane in cats.
OBJECTIVE
To determine the relationship between bispectral index (BIS) and minimum alveolar concentration (MAC) multiples of sevoflurane in cats.


METHODS
8 domestic cats.


METHODS
Each cat was anesthetized twice with sevoflurane. First, the MAC of sevoflurane for each cat was determined by use of the tail clamp method. Second, cats were anesthetized with sevoflurane at each of 5 MAC multiples administered in random order. Ventilation was controlled, and after a 15-minute equilibration period at each MAC multiple of sevoflurane, BIS data were collected for 5 minutes and the median value of BIS calculated.


RESULTS
The mean (+/- SD) MAC of sevoflurane was 3.3 +/- 0.2%. The BIS values at 0.5 MAC could not be recorded as a result of spontaneous movement in all 8 cats. The BIS values at 2.0 MAC were confounded by burst suppression in all 8 cats. Over the range of 0.8 to 1.5 MAC, BIS values decreased significantly with increasing end-tidal sevoflurane concentrations. Mean (+/- SD) BIS measurements were 30 +/- 3, 21 +/- 3, and 5 +/- 2 at 0.8, 1.0, and 1.5 MAC, respectively.


CONCLUSIONS
Values of BIS are inversely and linearly related to end-tidal sevoflurane concentrations in anesthetized cats, and BIS may be a useful predictor of CNS depression in this species. The consistently low BIS values recorded in this study suggest that clinical BIS end points used to titrate anesthetic agents in humans may not be applicable to cats.
Lamont
Leigh A
LA
Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61802, USA.
Greene
Stephen A
SA
Grimm
Kurt A
KA
Tranquilli
William J
WJ
D000769:Anesthesia, Inhalation / Q000662:veterinary*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure; D002415:Cats / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004569:Electroencephalography / Q000187:drug effects* / Q000662:veterinary*; D006339:Heart Rate; D008738:Methyl Ethers / Q000008:administration & dosage / Q000494:pharmacology*; D000077149:Sevoflurane
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane