Completing the Apnea Test: Decline in Complications

Introduction: The apnea test is a crucial component of the clinical diagnosis of brain death. Apprehension about hypoxemia, hypotension, and/or cardiac arrhythmias may sometimes lead clinicians to avoid performing or prematurely terminate the apnea test. The purpose of this study was to perform a contemporary re-evaluation of the safety of the apnea test.

Methods: We performed a detailed chart review of consecutive brain dead patients who underwent an apnea test from 2008 to 2012.

Results: Out of 63 patients, 33 were men (52.4 %). Mean age was 46.4 years. In all but four patients (93.7 %), the apnea test was performed by a neurointensivist. Infiltrates on chest radiographs were present in 34 (54 %). Seven patients (11.1 %) had chest tubes, six of which were associated with polytrauma. Echocardiograms were obtained in 47 patients (74.6 %), and 18 patients (38.3 %) had regional wall motion abnormalities (IQR 41-65 %). Fifty patients (79.4 %) were on vasopressors prior to apnea test. Median FiO2 was 0.5 (IQR 0.4-0.6), and PEEP was 5 cm H2O (IQR 5-10). After apnea test, median pO2 was 306 mmHg (IQR 121-389). Apnea test was aborted in only one patient; this patient had required FiO2 0.9-1.0 prior to the test and desaturated during the test. Mild hypoxemia occurred in three others without any consequences. Mild hypotension occurred in 11 patients (17.4 %) and was easily managed by an increase in the vasopressor infusion. There were no instances of major cardiac arrhythmias.

Conclusion: Apnea determined using the oxygenation diffusion method during brain death testing is very safe, provided appropriate prerequisites are met. We found a major decrease in the number of aborted or not attempted apnea tests compared to previous studies.