A 35-year-old male is brought to the emergency department in a state of deep coma following a severe head injury sustained in a motor vehicle acciden…

Brain death is a clinical diagnosis requiring the irreversible cessation of all functions of the entire brain, including the brainstem. Before brain death testing (including the apnea test) can be performed, prerequisites must be met: the etiology of coma must be known and sufficient to account for brain death, confounding factors must be excluded (such as severe electrolyte/acid-base disturbances, endocrine crisis, and drug intoxication or poisoning), and the core body temperature must be $\ge 35^\circ\text{C}$ (not 32). While EEG can be supportive, it is not mandatory for brain death determination in most jurisdictions.