Hospital Municipal São José, Unidade de Terapia Intensiva, Joinville, SC, Brasil.
Centro Hospitalar Unimed, Unidade de Terapia Intensiva, Joinville, SC, Brasil.
Rev Bras Ter Intensiva. 2020 Jun;32(2):319-325. doi: 10.5935/0103-507x.20200032. Epub 2020 Jun 24.
The apnea test, which involves disconnection from the mechanical ventilator, presents risks during the determination of brain death, especially in hypoxemic patients. We describe the performance of the apnea test without disconnection from the mechanical ventilator in two patients. The first case involved an 8-year-old boy admitted with severe hypoxemia due to pneumonia. He presented with cardiorespiratory arrest, followed by unresponsive coma due to hypoxic-ischemic encephalopathy. Two clinical exams revealed the absence of brainstem reflexes, and transcranial Doppler ultrasound revealed brain circulatory arrest. Three attempts were made to perform the apnea test, which were interrupted by hypoxemia; therefore, the apnea test was performed without disconnection from the mechanical ventilator, adjusting the continuous airway pressure to 10cmH2O and the inspired fraction of oxygen to 100%. The oxygen saturation was maintained at 100% for 10 minutes. Posttest blood gas analysis results were as follows: pH, 6.90; partial pressure of oxygen, 284.0mmHg; partial pressure of carbon dioxide, 94.0mmHg; and oxygen saturation, 100%. The second case involved a 43-year-old woman admitted with subarachnoid hemorrhage (Hunt-Hess V and Fisher IV). Two clinical exams revealed unresponsive coma and absence of all brainstem reflexes. Brain scintigraphy showed no radioisotope uptake into the brain parenchyma. The first attempt at the apnea test was stopped after 5 minutes due to hypothermia (34.9°C). After rewarming, the apnea test was repeated without disconnection from the mechanical ventilator, showing maintenance of the functional residual volume with electrical bioimpedance. Posttest blood gas analysis results were as follows: pH, 7.01; partial pressure of oxygen, 232.0mmHg; partial pressure of carbon dioxide, 66.9mmHg; and oxygen saturation, 99.0%. The apnea test without disconnection from the mechanical ventilator allowed the preservation of oxygenation in both cases. The use of continuous airway pressure during the apnea test seems to be a safe alternative in order to maintain alveolar recruitment and oxygenation during brain death determination.
在脑死亡判定过程中，脱机的呼吸暂停试验会带来风险，尤其是在低氧血症患者中。我们描述了在不脱机的情况下对两名患者进行呼吸暂停试验的情况。第一例患者为 8 岁男孩，因肺炎导致严重低氧血症入院。他发生了心肺骤停，随后因缺氧缺血性脑病出现无反应性昏迷。两次临床检查均发现脑干反射缺失，经颅多普勒超声显示脑循环停止。尝试了 3 次呼吸暂停试验，但均因低氧血症而中断；因此，在不脱机的情况下进行了呼吸暂停试验，将持续气道正压调整至 10cmH2O，吸入氧分数调至 100%。氧饱和度维持在 100%达 10 分钟。试验后血气分析结果如下：pH 值 6.90，氧分压 284.0mmHg，二氧化碳分压 94.0mmHg，氧饱和度 100%。第二例患者为 43 岁女性，因蛛网膜下腔出血（Hunt-Hess V 和 Fisher IV）入院。两次临床检查均发现无反应性昏迷，且所有脑干反射均缺失。脑闪烁扫描显示脑实质无放射性同位素摄取。第一次呼吸暂停试验在 5 分钟后因体温过低（34.9°C）而停止。复温后，在不脱机的情况下重复进行了呼吸暂停试验，结果显示用电生物阻抗保持了功能残气量。试验后血气分析结果如下：pH 值 7.01，氧分压 232.0mmHg，二氧化碳分压 66.9mmHg，氧饱和度 99.0%。在这两种情况下，不脱机的呼吸暂停试验都能保持氧合。在呼吸暂停试验中使用持续气道正压似乎是一种安全的替代方法，可以在脑死亡判定过程中保持肺泡复张和氧合。
