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 permanent irreversible coma loss of response to painful stimuli from brain-originating motor area loss of brainstem reflex e.g., corneal, pupillary, jaw-jerk, oculovestibular, gag reflex exclude metabolic, poisons, intoxication causes establish normothermia (> 97°F (> 36°C)) hypothermia may confound apnea test may require warming blanket establish normotension > 100 mmHg systolic may need vasopressors 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 or PaCO2 > 20 mmHg above baseline 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: EEG cerebral angiography "gold standard" nuclear scan transcranial Dopppler ultrasonography Differential Locked-in syndrome Hypothermia Drug intoxication Guillain-Barré syndrome