Definition

Brain death is characterized by irreversible brain injury, often stemming from causes such as subarachnoid hemorrhages, hypoxic-ischemic injury, and others.

Prerequisites

• check the level of sedation

• correct metabolic derangements eg. ammonia, blood urea nitrogen, ionized calcium, glucose, magnesium, potassium, sodium, pH, and T4 levels

• if cause of injury unknown, get imaging and wait till properly investigated

• ensure normal body temperature and blood pressure requirements

• exclusion of pharmacologic paralysis: this can include using a Train of Four muscle stimulator to ensure paralysis has worn off before brain death evaluation

• exclusion of confounding conditions such as Guillain-Barre syndrome, high cervical spine lesions, and botulism poisoning

• wait at least 5 half-lives for sedating medications to wear off. If concern for overdose, give it sufficient time

• alcohol blood level less than 80 mg/dL

• toxicology screen, blood and urine, should be negative

• wait at least 72 hours from time of injury

• be aware of variablity in local and institutional requirements

• obtain informed consent, communicate with family throughout

Clinical Exam

• absent corneal and pupillary reflexes

• absent cough and gag reflexes

• no motor responses to noxious stimuli. Spinal reflexes such as Lazarus sign and triple flexion may occur. Learn how to differentiate these from true withdrawal here

• absence of brainstem reflexes, including the oculocephalic (doll’s eyes) reflex and oculovestibular (cold caloric) reflex. Learn more on how to interpret these findings here

• apnea testing

  • involve ICU colleagues, preoxygenation with 100% oxygen, and obtaining arterial blood gas measurements before and after the procedure. Criteria for aborting apnea testing include hemodynamic instability, progressive decrease in oxygen saturations, cardiac arrhythmia with hemodynamic instability, and the patient spontaneously breathing.

Ancillary Testing

• required in cases where clinical exam or imaging may be inconclusive

• includes cerebral perfusion scans, four-vessel catheter angiography, and transcranial Doppler ultrasonography

• EEG and evoked potentials are no longer recommended

Listen to full episode with all the nuances of brain death determination here

Until next time, keep those synapses firing!