Right-to-left shunt determination in dog lungs under inhalation anesthesia with rebreathing and non-rebreathing system1 Determinação de shunt venoso–arterial em pulmões de cães sob anestesia geral inalatória por sistemas com e sem reinalação

Purpose: To investigatge right-to-left shunt determination in dog lungs under inhalantion anesthesia with non-rebreathing and rebreathing systems and fraction of inspired oxygen (FIO2) of 0.9 and 0.4, respectively. Methods: Two groups of 10 dogs each under inhalation anesthesia with sevoflurane: GI in which it was utilized non-rebreathing semiclosed system and FIO2 = 0.9, and GII in which it was utilized rebreathing semiclosed system and FIO2 = 0.4. The study parameters were: heart rate, medium arterial pressure, right-to-left intrapulmonary shunt, hematocrit, hemoglobin, arterial partial pressure of oxygen, mixed venous partial pressure of oxygen, mixed venous oxygen saturation, arterial partial pressure of carbon dioxide, partial pressure of water in the alveoli. Results: Shunt results were significantly different between the two groups – GI data were higher than GII in all the evaluated moments. Hence, the group with nonrebreathing (GI) developed a superior grade of intrapulmonary shunt when compared with the rebreathing group (GII). The partial pressure of water in the alveoli was significantly higher in GII. Conclusion: The inhalation anesthesia with non-rebreathing system and FIO2 = 0.9 developed a higher grade of intrapulmonary right-to-left shunt when compared with the rebreathing system and FIO2 = 0.4. The higher humidity in GII contributed to the result.