Apnea test in the determination of brain death in patients treated with extracorporeal membrane oxygenation (ECMO)

Abstract

Extracorporeal Membrane Oxygenation (ECMO) is a well-established method of support in patients with severe respiratory and/or circulatory failure. Unfortunately, this invasive method of treatment is associated with a high risk of neurological complications including brain death. Proper diagnosis of brain death is crucial for the termination of futile medical care. Currently, the legal system in Poland does not provide an accepted protocol for apnea tests for patients on ECMO support. Veno-arterial ECMO is particularly problematic in this regard because it provides both gas exchange and circulatory support. CO₂ elimination by ECMO prevents hypercapnia, which is required to perform an apnea test. Several authors have described a safe apnea test procedure in patients on ECMO. Maximal reduction of the sweep gas flow to the oxygenator should maintain an acceptable haemoglobin oxygenation level and reduce elimination of carbon dioxide. Hypercapnia achieved via this method should allow an apnea test to be conducted in the typical manner. In the case of profound desaturation and an inadequate increase in the arterial CO₂ concentration, the sweep gas flow rate may be increased to obtain the desired oxygenation level, and exogenous carbon dioxide may be added to achieve a target carbon dioxide level. Incorporation of an apnea test for ECMO patients is planned in the next edition of the Polish guidelines on the determination of brain death.

Keywords: ECMO; apnea test; brain death; diagnostics; extracorporeal circulation; organ donor.