Brazilian Journal of Anesthesiology
https://bjan-sba.org/article/doi/10.1590/S0034-70942003000100004
Brazilian Journal of Anesthesiology
Scientific Article

Avaliação da anestesia com baixo fluxo de gases, comparando ventilação com pressão controlada à ventilação com tempo controlado - pressão limitada e fluxo constante de gases: modelo experimental em coelhos

Evaluation of low flow anesthesia, comparing pressure-controlled ventilation to time-cycled pressure-limited continuous flow ventilation: experimental model in rabbits

Eliana Bonetti; Denise Tabacchi Fantoni; José Otávio Costa Auler Júnior

http://dx.doi.org/10.1590/S0034-70942003000100004 Braz J Anesthesiol, vol.53, n1, p.25-38, 2003
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Resumo

JUSTIFICATIVA E OBJETIVOS: Embora sejam amplamente conhecidas as vantagens que envolvem sistemas de anestesia com reinalação e baixo fluxo, estes ainda são pouco empregados em animais de pequeno porte e em pediatria. O modelo experimental deste estudo foi delineado, procurando-se avaliar a viabilidade do sistema com reinalação e fluxo de gases entre 500 e 1.000 ml.min-1 em animais de pequeno porte, bem como comparar a ventilação nos modos tempo controlado - pressão limitada e fluxo constante de gases, com a pressão controlada (PCV), em um novo equipamento desenvolvido para anestesia. MÉTODO: Dezesseis coelhos (fêmeas) foram distribuídos aleatoriamente em dois grupos (GI e GII), anestesiados com halotano, e submetidos à ventilação controlada mecânica. Em GI, permitiam-se ajustes nos parâmetros ventilatórios do ventilador (pressão de pico inspiratório, freqüência respiratória e tempo inspiratório), de forma a manter normocapnia, volume corrente entre 6 e 8 ml.kg-1, e pH sangüíneo arterial entre 7,35 e 7,45. Em GII, os ajustes eram realizados somente no momento controle. RESULTADOS: Verificou-se reinalação de dióxido de carbono em ambos os grupos ao se avaliar o sistema com reinalação, independente do modo de ventilação. O pH sangüíneo arterial manteve-se dentro dos parâmetros fisiológicos no grupo GI, e no GII verificou-se acidose respiratória ao se avaliar o sistema com reinalação durante a ventilação com pressão controlada. CONCLUSÕES: Com os resultados obtidos conclui-se que este sistema circular, em fluxos entre 500 e 1.000 ml.min-1, é uma alternativa em anestesia em pacientes de baixo peso, desde que a monitorização necessária seja feita. A eficiência da ventilação dependeu primariamente dos parâmetros ventilatórios ajustados, da complacência e resistência das vias aéreas, e nem tanto do modo de ventilação escolhido.

Palavras-chave

ANIMAL, EQUIPAMENTOS, EQUIPAMENTOS, EQUIPAMENTOS, VENTILAÇÃO

Abstract

BACKGROUND AND OBJECTIVES: Despite the well-known advantages of rebreathing systems and low flow anesthesia, they are seldom used in small animals and pediatric anesthesia. The experimental model of this study was designed to evaluate a rebreathing system with flows between 500 to 1,000 ml.min-1 in small animals, in addition to comparing time-controlled pressure-limited and constant gas flow ventilation to pressure-controlled ventilation in a new anesthesia machine. METHODS: Sixteen female rabbits were randomly allocated in two groups (GI and GII), anesthetized with halothane and submitted to mechanically-controlled ventilation. Adjustments in ventilatory parameters were allowed in GI (peak inspiratory pressure, respiratory rate and inspiratory time) to maintain normocapnia, tidal volume between 6 and 8 ml.kg-1 and arterial pH between 7.35 and 7.45. Adjustments in GII were only allowed at control moment. RESULTS: Carbon dioxide rebreathing was observed in both groups when rebreathing systems were evaluated, regardless of the ventilation mode. Arterial pH was maintained within physiologic parameters in GI, and respiratory acidosis was observed in GII when the rebreathing system was evaluated during pressure-controlled ventilation. CONCLUSIONS: According to our results, a circle system with flows between 500 and 1,000 ml.min-1 may be an alternative for low weight patients anesthesia, provided necessary monitoring is performed. Ventilation efficiency was primarily a function of adjusted ventilatory parameters, of airways compliance and resistance and not so much of the ventilation mode.

Keywords

ANIMAL, EQUIPMENTS, EQUIPMENTS, EQUIPMENTS, VENTILATION

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