Brazilian Journal of Anesthesiology
https://bjan-sba.org/article/doi/10.1590/S0034-70942003000600009
Brazilian Journal of Anesthesiology
Scientific Article

Efeitos cardiovasculares de duas doses de dexmedetomidina: estudo experimental em cães

Cardiovascular effects of two dexmedetomidine doses: experimental study in dogs

Nivaldo Ribeiro Villela; Paulo do Nascimento Júnior; Lídia Raquel de Carvalho

http://dx.doi.org/10.1590/S0034-70942003000600009 Braz J Anesthesiol, vol.53, n6, p.784-796, 2003
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Resumo

JUSTIFICATIVA E OBJETIVOS: A dexmedetomidina é um novo agonista alfa2-adrenérgico, havendo, atualmente, crescente interesse no seu uso em Anestesiologia, por reduzir o consumo de anestésicos e promover estabilidade hemodinâmica. O objetivo desta pesquisa foi estudar os efeitos cardiovasculares da dexmedetomidina no cão anestesiado, empregando-se duas doses distintas e semelhantes àquelas utilizadas em Anestesiologia. MÉTODO: 36 cães adultos anestesiados com propofol, fentanil e isoflurano foram divididos em três grupos: G1, injeção de 20 ml de solução de cloreto de sódio a 0,9%, em 10 minutos, seguida de injeção de 20 ml da mesma solução, em 1 hora; G2, injeção de 20 ml de solução de cloreto de sódio a 0,9% contendo dexmedetomidina (1 µg.kg-1), em 10 minutos, seguida de injeção de 20 ml da mesma solução, em 1 hora e G3, injeção de 20 ml de solução de cloreto de sódio a 0,9% contendo dexmedetomidina (2 µg.kg-1) em 10 minutos, seguida de injeção de 20 ml da mesma solução, em 1 hora. Estudaram-se os atributos cardiovasculares em quatro momentos: M1, controle; M2, após a injeção inicial de 20 ml da solução em estudo, em 10 minutos, coincidindo com o início da injeção da mesma solução, em 1 hora; M3, 60 minutos após M2 e M4, 60 minutos após M3. RESULTADOS: A freqüência cardíaca (FC) diminuiu no G2, no M2, retornando aos valores basais no M3, enquanto no G3 diminuiu no M2, mantendo-se baixa durante todo o experimento. No G1 houve aumento progressivo da FC. Em nenhum grupo houve alteração da pressão arterial. A resistência vascular sistêmica (RVS) manteve-se estável no G2 e G3, enquanto no G1 apresentou redução em M2, mantendo-se baixa ao longo do experimento. O índice cardíaco (IC) não apresentou alterações significativas no G2 e G3, mas aumentou progressivamente no G1. CONCLUSÕES: Conclui-se que no cão, nas condições experimentais empregadas, a dexmedetomidina diminui a FC de forma dose-dependente, inibe a redução da RVS produzida pelo isoflurano e impede a ocorrência de resposta hiperdinâmica durante o experimento.

Palavras-chave

ANIMAL, DROGAS, DROGAS

Abstract

BACKGROUND AND OBJECTIVES: There has been a growing interest in the anesthetic use of dexmedetomidine, a new alpha2-adrenergic agonist, due to decreased anesthetics consumption and better cardiovascular stability that it promoter. This study aimed at investigating cardiovascular effects of two different dexmedetomidine doses in anesthetized dogs. METHODS: The study involved 36 adult dogs anesthetized with propofol, fentanyl and isoflurane distributed in three groups which received: G1, 20 ml saline injection in 10 minutes, followed by 20 ml of the same solution infused in one hour; G2, 20 ml dexmedetomidine-containing saline (1 µg.kg-1) in 10 minutes, followed by 20 ml of the same solution infused one hour; and G3, of dexmedetomidine-containing saline (2 µg.kg-1) in 10 minutes, followed by 20 ml of the same solution infused in one hour. Cardiovascular attributes were evaluated in four moments: M1, control, M2, after initial 20 ml injection of the studied solution, coincident with the beginning of the same solution injection in one hour; M3, 60 minutes after M2 and M4, 60 minutes after M3. RESULTS: G2 heart hate (HR) was decreased at M2, returning to baseline values at M3, while in G3 it was decreased at M2 but was kept so throughout the experiment. There has been progressive HR increase in G1. There were no significant changes in mean blood pressure in all group. Systemic vascular resistance (SVR) was maintained stable in G2 and G3, but was decreased in G1 at M3. Cardiac index (CI) was not significantly changed in G2 and G3, but has progressively increased in G1. CONCLUSIONS: In dogs under these experimental conditions, dexmedetomidine has induced a dose-dependent HR decrease, has inhibited isoflurane-induced SVR decrease and has prevented hyperdynamic responses throughout the experiment.

Keywords

ANIMAL, DRUGS, DRUGS

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