Effects of nitrous oxide on minimum alveolar concentration of desflurane in dogs

Nishimori, Celina Tie; Nunes, Newton; Paula, Danielli Parrilha de; Rezende, Marlis L.; Souza, Almir Pereira de; Santos, Paulo Sérgio Patto dos

doi:10.1590/s0102-09352007000100017

Cited by 2 publications

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References 31 publications

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“…This finding is consistent with prior studies examining the MAC-sparing effect of N 2 O in other animal models and for different volatile anesthetic agents. In dogs, addition of 70% N 2 O decreased the MAC of isoflurane by 32% [ 10 ] and of desflurane by 16% [ 17 ]; and Steffey and co-workers [ 1 ] reported with 70% N 2 O an approximately 34, 31, and 37% MAC-reduction of halothane in dogs, cats, and stump-tail monkeys, respectively. The commonly reported 30–40% MAC-sparing effect of 60–75% N 2 O in animal species might be considered a modest reduction compared to the up to 75% decrease in MAC of volatile agents in human patients [ 8 , 9 , 18 ].…”

Section: Discussionmentioning

confidence: 99%

MAC-sparing effect of nitrous oxide in sevoflurane anesthetized sheep and its reversal with systemic atipamezole administration

et al. 2018

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IntroductionNitrous oxide (N2O) is an anesthetic gas with antinociceptive properties and reduces the minimum alveolar concentration (MAC) for volatile anesthetic agents, potentially through mechanisms involving central alpha2-adrenoceptors. We hypothesized that 70% N2O in the inspired gas will significantly reduce the MAC of sevoflurane (MACSEVO) in sheep, and that this effect can be reversed by systemic atipamezole.Materials and methodsAnimals were initially anesthetized with SEVO in oxygen (O2) and exposed to an electrical current as supramaximal noxious stimulus in order to determine MACSEVO (in duplicates). Thereafter, 70% N2O was added to the inspired gas and the MAC re-determined in the presence of N2O (MACSN). A subgroup of sheep were anesthetized a second time with SEVO/N2O for re-determination of MACSN, after which atipamezole (0.2 mg kg-1, IV) was administered for MACSNA determinations. Sheep were anesthetized a third time, initially with only SEVO/O2 to re-determine MACSEVO, after which atipamezole (0.2 mg kg-1, IV) was administered for determination of MACSA.ResultsMACSEVO was 2.7 (0.3)% [mean (standard deviation)]. Addition of N2O resulted in a 37% reduction of MACSEVO to MACSN of 1.7 (0.2)% (p <0.0001). Atipamezole reversed this effect, producing a MACSNA of 3.1 (0.7)%, which did not differ from MACSEVO (p = 0.12). MACSEVO did not differ from MACSA (p = 0.69). Cardiorespiratory variables were not different among experimental groups except a lower ETCO2 in animals exposed to SEVO/N2O.ConclusionsN2O produces significant MACSEVO-reduction in sheep; this effect is completely reversed by IV atipamezole confirming the involvement of alpha2-adrenoreceptors in the MAC-sparing action of N2O.

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