Adult Critical Care Specialty (ACCS) Practice Exam

What criteria should be used to diagnose clinical brain death in a patient with prolonged asystole?

1. Pupils nonreactive at 4-mm diameter

2. PaCO2 of 70 torr during apnea test

3. Lack of ocular reflexes to ice water

4. Cerebral angiogram with prominent hemispheric perfusion

The correct answer is: Pupils nonreactive at 4-mm diameter

To diagnose clinical brain death, specific neurological criteria must be met, and one key aspect is the examination of pupillary responses. The correct answer indicates that pupils being nonreactive at a diameter of 4 mm is a criterion used in confirming brain death. This nonreactivity reflects a loss of brainstem function, which is essential, as brain death is defined by the irreversible absence of all cerebral and brainstem activity. In the context of brain death, pupil reaction is important; typically, pupils should react to light. If they are nonreactive, especially when dilated and measuring around 4 mm, it constitutes part of the neurological examination that supports a diagnosis of brain death. While other findings may contribute to the overall assessment, they are not as definitive for the diagnosis. For example, elevated PaCO2 levels can indicate hypercapnia during an apnea test, but the criterion for brain death involves demonstrating absence of respiratory effort rather than just high levels of carbon dioxide alone. The lack of ocular reflexes to ice water can also indicate brainstem function impairment, but this test may not always be a standard criterion in assessing brain death. A cerebral angiogram showing prominent hemispheric perfusion would not support a diagnosis of brain death, as it implies