Brain death: physiology and determination

At a glance

• In every Australian state and territory, death is irreversible cessation of all function of the brain or irreversible cessation of circulation. Australia and New Zealand use a whole-brain standard.
• Brain death usually follows raised intracranial pressure: when ICP exceeds mean arterial pressure, cerebral perfusion stops and the brain dies from the top down, ending in brainstem herniation.
• Determination needs: a cause sufficient to explain it, preconditions met, an observation period, and then either clinical testing of brainstem function including an apnoea test, or imaging showing no brain blood flow.