Brazilian Journal of Anesthesiology
https://bjan-sba.org/article/doi/10.1590/S0034-70942013000200002
Brazilian Journal of Anesthesiology
Scientific Article

Efeitos do óxido nitroso em hipotensão controlada durante anestesia com baixo fluxo

The effects of nitrous oxide on controlled hypotension during low flow anesthesia

Semiha Barçı; n; Leyla Sahan; Dilsen Ornek; Fazilet Sahin; Oya Kilci; Serpil Deren; Gulay Erdogan; Canan Un; Mehmet Gamli; Bayazit Dikmen

http://dx.doi.org/10.1590/S0034-70942013000200002 Braz J Anesthesiol, vol.63, n2, p.170-177, 2013
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Resumo

JUSTIFICATIVA E OBJETIVOS: Investigamos o efeito do óxido nitroso (N2O) em hipotensão controlada durante anestesia com baixo fluxo (isoflurano-dexmedetomidina) em termos de hemodinâmica, consumo de anestésico e custos. MÉTODOS: Quarenta pacientes foram randomicamente alocados em dois grupos. Infusão de dexmedetomidina (0,1 µg.kg-1.min-1) foi mantida por 10 minutos. Subsequentemente, essa infusão foi mantida até os últimos 30 minutos de operação a uma dose de 0,7 µg.kg-1.hora-1. Tiopental (4-6 mg.kg-1) e brometo de vecurônio (0,08 0,12 mg.kg-1) foram administrados na indução de ambos os grupos. Isoflurano (2%) foi administrado para manutenção da anestesia. O Grupo N recebeu uma mistura de 50% de O2-N2O e o Grupo A recebeu uma mistura de 50% de O2-ar como gás de transporte. Anestesia com baixo fluxo (1 L.min-1) foi iniciada após um período de 10 minutos de alto fluxo inicial (4,4 L.min-1). Os valores de pressão arterial, frequência cardíaca, saturação periférica de O2, isoflurano inspiratório e expiratório, O2 inspiratório e expiratório, N2O inspiratório e expiratório, CO2 inspiratório, concentração de CO2 após expiração e concentração alveolar mínima foram registrados. Além disso, as taxas de consumo total de fentanil, dexmedetomidina e isoflurano, bem como de hemorragia, foram determinadas. RESULTADOS: A frequência cardíaca diminuiu em ambos os grupos após a carga de dexmedetomidina. Após a intubação, os valores do Grupo A foram maiores nos minutos um, três, cinco, 10 e 15. Após a intubação, os valores de hipotensão desejados foram alcançados em 5 minutos no Grupo N e em 20 minutos no grupo A. Os valores da CAM foram mais altos no Grupo N nos minutos um, três, cinco, 10 e 15 (p < 0,05). Os valores da FiO2 foram mais altos entre 5 e 60 minutos no Grupo A, enquanto foram mais altos no Grupo N aos 90 minutos (p < 0,05). Os valores de Fi Iso (isoflurano inspiratório) foram menores no Grupo N nos minutos 15 e 30 (p < 0,05). CONCLUSÃO: O uso de dexmedetomidina em vez de óxido nitroso em anestesia com isoflurano pela técnica de baixo fluxo atingiu os níveis desejados de pressão arterial média (PAM), profundidade suficiente da anestesia, estabilidade hemodinâmica e parâmetros de inspiração seguros. A infusão de dexmedetomidina com oxigênio-ar medicinal como gás de transporte é uma técnica anestésica opcional.

Palavras-chave

ANALGÉSICOS, Dexmedetomidina, ANESTÉSICOS, Gasoso, óxido nitroso, HIPOTENSÃO CONTROLADA, TÉCNICAS ANESTÉSICAS, Geral, inalatória, baixo fluxo

Abstract

BACKGROUND AND OBJECTIVES: We investigated the effect of Nitrous Oxide (N2O) on controlled hypotension in low-flow isoflurane-dexmedetomidine anesthesia in terms of hemodynamics, anesthetic consumption, and costs. METHODS: We allocated forty patients randomly into two equal groups. We then maintained dexmedetomidine infusion (0.1 µg.kg-1.min-1) for 10 minutes. Next, we continued it until the last 30 minutes of the operation at a dose of 0.7 µg.kg-1.hour-1. We administered thiopental (4-6 mg. kg-1) and 0.08-0.12 mg.kg-1 vecuronium bromide at induction for both groups. We used isoflurane (2%) for anesthesia maintenance. Group N received a 50% O2-N2O mixture and Group A received 50% O2-air mixture as carrier gas. We started low-flow anesthesia (1 L.min-1) after a 10-minute period of initial high flow (4.4 L.min-1). We recorded values for blood pressure, heart rate, peripheral O2 saturation, inspiratory isoflurane, expiratory isoflurane, inspiratory O2, expiratory O2, inspiratory N2O, expiratory N2O, inspiratory CO2, CO2 concentration after expiration, Minimum Alveolar Concentration. In addition, we determined the total consumption rate of fentanyl, dexmedetomidine and isoflurane as well as bleeding. RESULTS: In each group the heart rate decreased after dexmedetomidine loading. After intubation, values were higher for Group A at one, three, five, 10, and 15 minutes. After intubation, the patients reached desired hypotension values at minute five for Group N and at minute 20 for group A. MAC values were higher for Group N at minute one, three, five, 10, and 15 (p < 0.05). FiO2 values were high between minute five and 60 for Group A, while at minute 90 Group N values were higher (p < 0.05). Fi Iso (inspiratuvar isofluran) values were lower in Group N at minute 15 and 30 (p < 0.05). CONCLUSION: By using dexmedetomidine instead of nitrous oxide in low flow isoflurane anesthesia, we attained desired MAP levels, sufficient anesthesia depth, hemodynamic stability and safe inspiration parameters. Dexmedetomidine infusion with medical air-oxygen as a carrier gas represents an alternative anesthetic technique.

Keywords

Hypotension, Controlled, Anesthesia, Closed-Circuit, Nitrous Oxide, Dexmedetomidine

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