Apnea test during brain death assessment in mechanically ventilated and ECMO patients

Purpose: To evaluate the feasibility and efficacy of an apnea test (AT) technique that combines the application of positive end expiratory pressure (PEEP) with subsequent pulmonary recruitment in a large cohort of brain-dead patients.

Methods: This study was a retrospective analysis of prospectively collected data on brain-dead patients admitted to our institution (Hospital San Gerardo, Monza, Italy) between January 2010 and December 2014. The rate of aborted apnea tests (ATs), occurrence of complications (i.e., pneumothorax, cardiac arrhythmias, cardiac arrest, and severe hypoxia, defined as PaO2 < 40 mmHg), ventilator settings, hemodynamics, and blood gas analyses were evaluated. Subgroup analysis was performed, with patients classified into veno-arterial extracorporeal membrane oxygenation (ECMO) or non-ECMO groups, and into hypoxic (i.e., baseline PaO2/FiO2 < 200 mmHg) and non-hypoxic (i.e., baseline PaO2/FiO2 > 200 mmHg) groups.

Results: In total, 169 consecutive patients including 25 on ECMO were included in the study. No AT abortion nor severe complications were detected. The AT was completed in all patients. Fluid boluses and increases or initiation of vasoactive drugs were required in less than 10 and 3% of the AT procedures, respectively. No clinically meaningful alteration in hemodynamics was recorded. Severe hypoxia occurred during 7 (2.4%) and 4 (8%) of the ATs performed in non-ECMO and ECMO patients, respectively (p = 0.063), and it occurred more frequently in hypoxic patients than in non-hypoxic patients (11.1 vs. 4.8%, respectively; p = 0.002).

Conclusions: In a large cohort of consecutive patients, including the largest patient population on ECMO reported to date, our AT technique that combines the application of PEEP with subsequent pulmonary recruitment proved to be feasible and safe.