Apnea test for brain death determination in a patient on extracorporeal membrane oxygenation

Apnea test is a key component to confirm brain death. For patients receiving extracorporeal membrane oxygenation (ECMO), apnea test remains challenging. Brain death (BD) diagnosis is often made without apnea test.

We report the case of a 29-year-old man presenting clinical signs of BD while treated with ECMO therapy for refractory cardiogenic shock. Decreasing the ECMO sweep gas flow from 3 to 1 L/min and increasing oxygen delivery to 100% on ECMO during the apnea test have allowed increasing the PaCO2 of more than 20 mmHg without decreasing PaO2.

In order to diagnose BD, neurological examination should be complete, including apnea testing, which can be not possible in patients receiving ECMO due to CO2 removal from the membrane. Decreasing sweep gas rate allows reduction in CO2 diffusion through the membrane. However, decreasing the ECMO gas flow to zero could be insufficient to maintain normoxemia. Decreasing (but not stopping) the sweep gas flow to 1 L/min and increasing the oxygen delivery through the ECMO have allowed performing the apnea test safely.

To assess brain death in patients on ECMO, apnea test can be performed without compromising oxygenation by decreasing (but not stopping) the sweep gas flow and increasing oxygen delivery through the membrane.