The aim of this study was to determine the minimum anesthetic concentration of isoflurane (MAC_ISO) and sevoflurane (MAC_SEVO) and evaluate the cardiorespiratory changes induced by varying fractions of inspired oxygen (FiO₂) in Magellanic penguins (Spheniscus magellanicus). Twenty adult penguins (3.53 ± 0.44 kg) of undetermined sex were used. Both MAC_ISO (n = 9) and MAC_SEVO (n = 13) were established using an up-and-down design. Next, twelve mechanically ventilated penguins were maintained at 1 MAC_ISO or 1 MAC_SEVO (n = 6 per group) with the FiO₂ initially set at 1.0. Three FiO₂ values (0.6, 0.4 and 0.2) were then held constant during anesthesia for 20 minutes each. Arterial blood samples were collected for gas analysis after the 20-minute period for each FiO₂. Mean ± SD MAC_ISO was 1.93 ± 0.10% and MAC_SEVO was 3.53 ± 0.13%. Other than heart rate at 0.6 FiO₂ (86 ± 11 beats/minute in MAC_ISO and 132 ± 37 beats/minute in MAC_SEVO; p = 0.041), no significant cardiorespiratory differences were detected between groups. In both groups, decreasing the FiO₂ produced increased pH values and reduced partial pressures of carbon dioxide and bicarbonate. Partial pressures of oxygen (PaO₂) gradually lowered from 1.0 FiO₂ through 0.2 FiO₂, though hypoxemia (PaO₂ < 80 mmHg) occurred only with the latter FiO₂. The MAC_ISO and the MAC_SEVO for the Magellanic penguin fell within the upper range of reported avian MAC estimates. To prevent hypoxemia in healthy, mechanically ventilated, either isoflurane- or sevoflurane-anesthetized Magellanic penguins, a minimum FiO₂ of 0.4 should be used.

本研究的目的是确定异氟烷 (MAC _ISO ) 和七氟烷 (MAC _SEVO ) 的最低麻醉浓度，并评估麦哲伦企鹅 ( Spheniscus magellanicus ) 不同吸入氧分数 (FiO ₂ )引起的心肺变化。使用二十只性别未定的成年企鹅（3.53 ± 0.44 kg）。MAC _ISO ( n  = 9) 和 MAC _SEVO ( n  = 13) 都是使用上下设计建立的。接下来，将 12 只机械通气企鹅维持在 1 MAC _ISO或 1 MAC _SEVO（每组n  = 6 只），FiO ₂初始设置为 1.0。然后三个FiO ₂值（0.6、0.4和0.2）在麻醉期间保持恒定，每个值20分钟。_{每个FiO 2} 20分钟后收集动脉血样用于气体分析。平均值±SD MAC _ISO为1.93±0.10%，MAC _SEVO为3.53±0.13%。_{除了 0.6 FiO 2}的心率（MAC _ISO中为 86 ± 11 次/分钟，MAC _SEVO中为 132 ± 37 次/分钟；p  = 0.041）外，组间未检测到显着的心肺差异。在两组中，降低 FiO ₂都会增加 pH 值并降低二氧化碳和碳酸氢盐的分压。氧分压(PaO _{2 )从1.0 FiO 2}逐渐降低到0.2 FiO ₂，​​尽管低氧血症(PaO ₂  < 80 mmHg)仅在后者的FiO ₂中发生。麦哲伦企鹅的MAC _ISO和 MAC _SEVO落在报告的鸟类 MAC 估计值的上限范围内。为了防止健康、机械通气、异氟烷或七氟烷麻醉的麦哲伦企鹅发生低氧血症，应使用最低 0.4 的 FiO _{2 。}