Uso da CPAP como alternativa para realização do teste de apneia durante determinação da morte encefálica em pacientes hipoxêmicos. Relato de dois casos / Use of CPAP as an alternative to the apnea test during the determination of brain death in hypoxemic patients. Report of two cases

RESUMO O teste de apneia com desconexão do ventilador mecânico representa riscos durante a determinação da morte encefálica, especialmente em pacientes hipoxêmicos. Descrevemos a realização do teste de apneia sem desconexão do ventilador mecânico em dois pacientes. O primeiro caso é o de um menino de 8 anos, admitido com hipoxemia grave por pneumonia. Apresentou parada cardiorrespiratória, seguida de coma não responsivo por encefalopatia hipóxico-isquêmica. Dois exames clínicos constataram ausência de reflexos de tronco, e o Doppler transcraniano revelou parada circulatória encefálica. Realizaram-se três tentativas de teste de apneia, que foram interrompidas por hipoxemia, sendo então realizado teste de apneia sem desconexão do ventilador mecânico, ajustando a pressão contínua nas vias aéreas em 10cmH2O e fração inspirada de oxigênio em 100%. A saturação de oxigênio manteve-se em 100% por 10 minutos. A gasometria pós-teste foi a seguinte: pH de 6,90, pressão parcial de oxigênio em 284,0mmHg, pressão parcial de dióxido de carbono em 94,0mmHg e saturação de oxigênio em 100%. O segundo caso é de uma mulher de 43 anos, admitida com hemorragia subaracnóidea (Hunt-Hess V e Fisher IV). Dois exames clínicos constataram coma não responsivo e ausência de todos os reflexos de tronco. A cintilografia cerebral evidenciou ausência de captação de radioisótopos no parênquima cerebral. A primeira tentativa do teste de apneia foi interrompida após 5 minutos por hipotermia (34,9oC). Após reaquecimento, o teste de apneia foi repetido sem desconexão do ventilador mecânico, evidenciando-se manutenção do volume residual funcional com tomografia de bioimpedância elétrica. Gasometria pós-teste de apneia apresentava pH em 7,01, pressão parcial de oxigênio em 232,0mmHg, pressão parcial de dióxido de carbono 66,9mmHg e saturação de oxigênio em 99,0%. O teste de apneia sem desconexão do ventilador mecânico permitiu a preservação da oxigenação em ambos os casos. O uso de pressão contínua nas vias aéreas durante o teste de apneia parece ser uma alternativa segura para manter o recrutamento alveolar e a oxigenação durante determinação da morte encefálica.

ABSTRACT 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.

An Investigation and Suggestions for the Improvement of Brain Death Determination in China / 中华医学杂志(英文版)

Background@#Brain death is the irreversible cessation of the function of the brain including the brainstem. In 2013, the Brain Injury Evaluation Quality Control Centre (BQCC) of the National Health and Family Planning Commission issued criteria and practical guidelines for the determination of brain death. This study aimed to evaluate whether the institutions have adopted these guidelines and to make suggestions for the improvement of the current criteria and practical guidelines for brain death determination in China.@*Methods@#Consecutive brain death cases from 44 hospitals were evaluated for summary statistics for the following data: the performance of BQCC criteria and practical guidelines, clinical examination, apnea testing, ancillary testing, and the number of examinations as well as the waiting periods between examinations and details of who determined brain death. Data analysis was conducted from January 2013 to December 2017.@*Results@#A total of 550 cases were obtained. All patients were determined to have deep coma and met the prerequisites for clinical testing. The performance rates of four brainstem reflex examinations (except cough reflex) ranged from 97.5% to 98.0%, and the completion rate as well as the coincidence rate were both 100.0%. The 238 cases (50.7%) completed apnea testing, and 231 cases (42.0%) had to stop apnea testing during the examination because of instability. The performance rates of the three ancillary tests, including electroencephalogram, short-latency somatosensory evoked potential, and transcranial Doppler, were 89.5%, 67.5%, and 79.5%, respectively; furthermore, the coincidence rates were 98.6%, 96.5%, and 99.5%, respectively. The combination of two ancillary tests was more accurate than one single ancillary test. A total of 401 (72.9%) cases successfully underwent two separate examinations to determine brain death with at least a 12-h waiting period. All brain death cases were determined by at least two qualified physicians.@*Conclusion@#This study might provide suggestions for brain death determination in China.