title: Minimum alveolar concentration of I-653 and isoflurane in pigs: definition of a supramaximal stimulus.
abstract: We determined the anesthetic potencies of a new fluorinated anesthetic, I-653, and isoflurane in pigs as a preliminary to a study of the relative cardiovascular and electroencephalographic effects of these agents. Clamps were sequentially applied to the dew claw and/or tail of each animal to determine the minimum alveolar concentration (MAC) that suppressed movement in response to each of these stimuli. MAC obtained by clamping the tail (8.28 +/- 1.34% [mean +/- standard deviation] for I-653 and 1.65 +/- 0.36% for isoflurane) was more variable and lower than MAC obtained by clamping the dew claw (10.00 +/- 0.94% for I-653 and 2.04 +/- 0.19% for isoflurane). We conclude that the type of stimulus applied affects the MAC value obtained for I-653 and isoflurane. Clamping the tail is not a supramaximal stimulus in pigs; a greater stimulus is provided by clamping the dew claw.
authors.affiliation: Department of Anesthesia, University of California, San Francisco 94143-0464.
authors.forename: E I
authors.initials: EI
authors.lastname: Eger
authors.forename: B H
authors.initials: BH
authors.lastname: Johnson
authors.forename: R B
authors.initials: RB
authors.lastname: Weiskopf
authors.forename: M A
authors.initials: MA
authors.lastname: Holmes
authors.forename: N
authors.initials: N
authors.lastname: Yasuda
authors.forename: A
authors.initials: A
authors.lastname: Targ
authors.forename: I J
authors.initials: IJ
authors.lastname: Rampil
mesh_terms: D000777:Anesthetics / Q000378:metabolism*; D000818:Animals; D000077335:Desflurane; D007530:Isoflurane / Q000031:analogs & derivatives* / Q000378:metabolism; D008026:Ligation; D010147:Pain Measurement; D011650:Pulmonary Alveoli / Q000378:metabolism*; D013552:Swine
chemical_list: D000777:Anesthetics; D000077335:Desflurane; D007530:Isoflurane