Snapshot A previously healthy 46-year-old female presents to the emergency department after a motor vehicle accident. The patient is unresponsive to noxious stimuli. Pupils are dilated and unresponsive to light. Oculovestibular and gag reflexes are absent. The patient is intubated due to loss of spontaneous respirations. After further workup, an apnea test is performed, which shows no respiratory response with a PaCO2 > 60 mm Hg. Introduction Irreversible brain function brain death = death to determine brain death, one must do the following: neurologic exam login to view 5 more bullets exclude metabolic, poisons, intoxication causes establish normothermia (> 97°F (> 36°C)) login to view 3 more bullets establish normotension login to view 2 more bullets should know the cause of brain death Etiologies Cardiopulmonary arrest inadequate or delayed resuscitation Traumatic brain injury Subarachnoid hemorrhage Ischemic or hemorrhagic process can be a focal or global process Evaluation Clinical diagnosis see above presence of spinal cord reflexes is still compatible with brain death Apnea testing performed after brain death criteria is met e.g., eucapnia, normothermia, normotension, absence of hypoxia to display absence of respiratory drive no respiratory response with a PaCO2 > 60 mmHg login to view 1 more bullet invalid in CO2 retainers e.g, chronic obstructive pulmonary disease (COPD) Ancillary testing performed when unable to do apnea testing, or neurological exam is unreliable tests include: login to view 4 more bullets Differential Locked-in syndrome Hypothermia Drug intoxication Guillain-Barré syndrome