A negative apnea test means that the patient does not breathe spontaneously when disconnected from the ventilator and exposed to a high level of carbon dioxide, which normally stimulates breathing. A negative apnea test is one of the criteria for brain death, as it indicates the loss of brainstem function. A positive vestibulo-ocular reflex, also known as the oculocephalic or doll’s eye reflex, means that the eyes move in the opposite direction of the head when the head is turned. A positive cough reflex means that the patient coughs when the trachea is stimulated. A negative cold caloric test means that the eyes do not move when cold water is injected into the ear canal. All these tests assess the integrity of the brainstem, and a positive result would exclude brain death. Therefore, the correct answer is B.
References:
Diagnosis of brain death - UpToDate, under “Apnea testing”.
Brain Death | Critical Care Medicine | JAMA | JAMA Network, under “How Is Brain Death Diagnosed?”.
The 2023 AAN/AAP/CNS/SCCM Pediatric and Adult Brain Death/Death by …, under “Apnea Testing”.
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