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Revista Brasileira de Anestesiologia
On-line version ISSN 1806-907X
BONETTI, Eliana; FANTONI, Denise Tabacchi and AULER JUNIOR, José Otávio Costa. Evaluation of low flow anesthesia, comparing pressure-controlled ventilation to time-cycled pressure-limited continuous flow ventilation: experimental model in rabbits. Rev. Bras. Anestesiol. [online]. 2003, vol.53, n.1, pp. 25-38. ISSN 1806-907X. http://dx.doi.org/10.1590/S0034-70942003000100004.
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 [rabbit]; EQUIPMENTS [Anesthesia machine]; EQUIPMENTS [respiratory systems]; EQUIPMENTS [low-flow]; VENTILATION [mechanical controlled].