The use of apnea test and brain death determination in patients on extracorporeal membrane oxygenation: A systematic review

Objective: To review practices of brain death (BD) determination in patients on extracorporeal membrane oxygenation (ECMO). Methods: A systematic search was applied to PubMed and 6 electronic databases from inception to May 22, 2019. Studies reporting methods of BD assessment in adult patients (>18 years old) while on ECMO were included, after which data regarding BD assessment were extracted. Results: Twenty-two studies (n = 177 patients) met the inclusion criteria. Eighty-eight patients (50%) in 19 studies underwent the apnea test (AT); most commonly through decreasing the ECMO sweep flow in 14 studies (n = 42, 48%), followed by providing CO₂ through the ventilator in 2 studies (n = 6, 7%), and providing CO² through the ECMO oxygenator in 1 study (n = 1, 1%). The details of the AT were not reported in 2 studies (n = 39, 44%). In 19 patients (22%), the AT was nonconfirmatory due to hemodynamic instability, hypoxia, insufficient CO₂ rise, or unreliability of the AT. A total of 157 ancillary tests were performed, including electroencephalogram (62%), computed tomography angiography (22%), transcranial Doppler ultrasound (6%), cerebral blood flow nuclear study (5%), cerebral angiography (4%), and other (1%). Forty-seven patients (53% of patients with AT) with confirmatory AT still underwent additional ancillary for BD confirmation. Only 21 patients (12% of all patients) were declared brain-dead using confirmatory ATs alone without ancillary testing. Conclusions: Performing AT for patients with ECMO was associated with high failure rate and hemodynamic complications. Our study highlights the variability in practice in regard to the AT and supports the use of ancillary tests to determine BD in patients on ECMO.