Carbogen: A Safe and Effective Method for Apnea Testing to Declare Brain Death

Abstract Objective In addition to a clinical exam, apnea testing is critical for confirmation of cessation of neurologic function [brain death]. However, traditional apnea exams place clinicians in a difficult position where maintaining oxygenation and hemodynamic stability in patients who are typically unstable have been associated with adverse events such as hypoxia, hypotension, pneumothorax, arrhythmias, derecruitment, and even cardiac death. The purpose of this retrospective case series was to assess whether apnea testing using carbogen was a safe, reliable alternative. Methods A retrospective chart review was conducted of brain death exams and apnea tests performed for brain death determination in a university hospital and trauma center. Apnea tests were completed either using the “Traditional Method” (TM) by removing the patient from the ventilator and assessed for presence of spontaneous breathing by movement of the chest wall or the “Carbogen Method” (CM) where patients remain on the ventilator with two machine breaths per minute to deliver carbogen gas mixture and waveform graphics in addition to the patient’s chest wall were assessed for presence of spontaneous breathing. An arterial blood gas was used with both methods to determine if the necessary rise in PaCO 2 occurred. However, with the CM, a formula is used to determine the necessary target PaCO 2 level to be reached for completion of the apnea test rather than the clinician deciding when to draw the blood gas. Results Apnea tests were performed on 205 patients, n = 159 using CM and n = 46 using TM. Adverse events during and immediately after the exam were significantly less (p = .000) using CM than with TM. Although there was no statistically significant difference in the duration of the apnea test comparing the CM and TM, the test duration was significantly less in the Airway Pressure Release Ventilation (APRV) group versus other modes when using the CM. Patients in the CM group had a significantly higher vasopressor dependency index than the TM group (p = .004). Conclusion These data suggest the Carbogen Method is safe, efficient, and an alternative solution to the traditional method of apnea testing to confirm cessation of neurologic function [brain death] resulting in fewer adverse events.