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Updated: Nov 16 2021

Brain Death Diagnosis

  • 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
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