Brazilian Journal of Anesthesiology
https://bjan-sba.org/article/doi/10.1590/S0034-70942004000200009
Brazilian Journal of Anesthesiology
Scientific Article

Análise macroscópica infra-vermelha da difusão do óxido nitroso via inalatória para a cavidade abdominal, em ratos submetidos a pneumoperitônio

Macroscopic infrared analysis of inhaled nitrous oxide diffusion to abdominal cavity in rats submitted to pneumoperitoneum

Daniel Colman; Marcos Leal Brioschi; Mário Cimbalista Júnior; Elizabeth Mila Tambara; Maria Célia Barbosa Fabrício de Melo; Leonardo Pimpão Blume

http://dx.doi.org/10.1590/S0034-70942004000200009 Braz J Anesthesiol, vol.54, n2, p.218-228, 2004
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Resumo

JUSTIFICATIVA E OBJETIVOS: O óxido nitroso (N2O), por ser uma estrutura tri-atômica assimétrica, assume características de alta emissão e absorção de energia no espectro infra-vermelho, com um pico característico de absorção em 4,5 µm, o que o torna visível ao infra-vermelho curto, quando contrastado com uma fonte emissora de calor (anteparo quente). Diversos autores têm descrito a difusão do N2O para cavidades fechadas por métodos como cromatografia gasosa e analisador de gases, que não permitem um estudo macroscópico detalhado do gás. O presente estudo teve como objetivo a filmagem macroscópica no espectro infra-vermelho da difusão de N2O, utilizado em anestesia inalatória, para a cavidade peritoneal de ratos submetidos a pneumoperitônio de 20 mmHg com ar ambiente. MÉTODO: Dividiu-se os animais em três grupos, de acordo com o anestésico utilizado: I - controle venoso: tiopental intra-peritoneal; II - controle inalatório: isoflurano a 1,2% em O2 100%; III - óxido nitroso: N2O 66% em oxigênio e isoflurano a 0,6%. Os termogramas provenientes da descompressão abdominal foram obtidos, por meio de um radiômetro AGEMA 550 filmados a 7 quadros por segundo. RESULTADOS: O N2O demonstrou-se visível ao infra-vermelho. No momento da descompressão abdominal, não houve nos grupos I e II termogramas com rastros de gases visíveis ao infra-vermelho. Houve, porém, rastros de gases visíveis ao infra-vermelho no grupo III. CONCLUSÕES: Conclui-se que o óxido nitroso inalatório a 66% difundiu-se para a cavidade peritoneal de ratos submetidos a pneumoperitônio de 20 mmHg com ar ambiente, sem aumento de pressão intra-abdominal.

Palavras-chave

ANESTÉSICOS, ANESTÉSICOS, ANIMAL, TÉCNICAS DE MEDIÇÃO

Abstract

BACKGROUND AND OBJECTIVES: Nitrous oxide (N2O), for its tri-atomic asymmetric structure, has high energy emission and absorption characteristics within the infrared spectrum, with maximum absorption at 4.5 µm, what makes it visible at short infrared, when contrasted with a heat emission source (hot support). Many authors have described N2O diffusion to closed cavities by chromatography methods and gas analyzers, which do not allow a detailed macroscopic study of the gas. This study aimed at macroscopically filming in the infrared spectrum inhaled N2O diffusion to the peritoneal cavity of rats submitted to 20 mmHg room air pneumoperitoneum. METHODS: Animals where divided in three groups according to the anesthetic drug: I - Intravenous control: intraperitoneal thiopental; II - inhaled control: 1.2% isoflurane in 100% O2; III - nitrous oxide: 66% N2O in oxygen and 0.6% isoflurane. Thermal images of abdominal decompression where captured by an AGEMA 550 radiometer filmed at 7 frames per second. RESULTS: N2O was visible to infrared. At abdominal decompression, groups I and II have not shown visible gas traces at infrared thermographs, while group III had visible infrared traces. CONCLUSIONS: Our conclusion was that 66% inhaled nitrous oxide has diffused to peritoneal cavity of rats submitted to 20 mmHg room air pneumoperitoneum, with no intra-abdominal pressure increase.

Keywords

ANESTHETICS, ANESTHETICS, ANIMAL, MEASUREMENT TECHNIQUES

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