• Reza Seddighi, Christine M Egger, Barton W Rohrbach, Meredith Hobbs, and Thomas J Doherty.
• Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA. mrsed@utk.edu
• Am. J. Vet. Res. 2012 Mar 1;73(3):341-5.

ObjectiveTo investigate the effects of the concurrent administration of 70% N(2)O on the minimum alveolar concentration (MAC) for sevoflurane in dogs, the MAC derivative that blocks motor movement (MAC(NM)), and the MAC derivative that blocks autonomic responses (MAC(BAR)).Animals7 adult sexually intact male mixed-breed dogs.ProceduresFor each dog, anesthesia was induced with sevoflurane delivered via a face mask. Initially, the baseline MAC, MAC(NM), and MAC(BAR) for sevoflurane were determined by use of a noxious stimulus (50 V, 50 Hz, and 10 milliseconds) applied subcutaneously over a midulnar region. Nitrous oxide (70%) was added to the breathing circuit, and MAC, MAC(NM), and MAC(BAR) were determined again. Percentage changes from the respective baseline concentrations for MAC, MAC(NM)' and MAC(BAR) were calculated after the administration of N(2)O.ResultsBaseline median values for the MAC, MAC(NM), and MAC(BAR) for sevoflurane were 1.75%, 2.00%, and 2.50%, respectively. Addition of 70% N(2)O significantly decreased MAC, MAC(NM), and MAC(BAR) by 24.4%, 25.0%, and 35.2%, respectively, and these values did not differ significantly from each other.Conclusions And Clinical RelevanceSupplementation with 70% N(2)O caused a clinically important and significant decrease in the MAC, MAC(NM)' and MAC(BAR) for sevoflurane in dogs.

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