Brain death (death by neurological criteria) represents the irreversible cessation of ALL functions of the entire brain, including the brainstem. The NP must understand the pathophysiology that leads to brain death and the rigorous clinical assessment protocol required for determination. Pathophysiology of brain death: Catastrophic brain injury (massive intracerebral hemorrhage, severe traumatic brain injury, anoxic brain injury, large hemispheric ischemic stroke with herniation) causes progressive intracranial hypertension. As intracranial pressure (ICP) rises and approaches or exceeds mean arterial pressure (MAP), cerebral perfusion pressure (CPP = MAP - ICP) drops to zero. Without perfusion, global cerebral ischemia produces irreversible neuronal death throughout the cerebrum, cerebellum, and brainstem. The brainstem is the last structure to fail, and its death eliminates all cranial nerve reflexes, spontaneous respiratory drive (medullary respiratory center), and consciousness (reticular activating system). Prerequisites before brain death testing: (1) Established etiology of coma — neuroimaging must demonstrate a catastrophic structural brain lesion consistent with the clinical examination; if no structural cause is evident, brain death cannot be declared. (2) Exclusion of confounding conditions that may mimic brain death: hypothermia (core...