Prolonged duration of apnea test during brain death examination in a case of intraparenchymal hemorrhage.

OBJECTIVE: Apnea test is required as part of the brain death examination. The duration of the apnea test is variable but typically requires 8-10 min. Prolonged apnea tests have been reported in the setting of hypothermia. Here, we describe a case of prolonged duration of apnea test secondary to a phenomenon called cardiac ventilation.

METHODS: The patient presented in coma with brainstem areflexia after having an intracerebral hemorrhage resulting in subfalcine, central, uncal, and tonsillar herniations. Confounding variables were excluded. Brain death testing was performed, and she was found to have brainstem areflexia. Pre-requisites for apnea test were then met.

RESULTS: Apnea testing, however, was prolonged at 110 min. When reconnected to ventilator, it was noted that she had small (30-35 cc) tidal volumes at a rate of her heart rate without respiratory effort. Ancillary testing with four-vessel cerebral angiogram confirmed cerebral circulatory arrest.

CONCLUSIONS: To our knowledge, this is the longest reported case of apnea testing during brain death testing. Variables known to cause a delay in the rise of carbon dioxide (PaCO2) levels were excluded. We suspect the hyperdynamic cardiac state caused cardiac ventilations resulting in slow increase in carbon dioxide levels.