From the Guidelines
Brain death in the ICU should be determined based on a clinical diagnosis of the absence of neurologic function with a known irreversible cause of coma, with two examinations including apnea testing separated by an observation period, as outlined in the 2011 guidelines by the Pediatrics journal 1. The key criteria for determining brain death include:
- Establishing a known irreversible cause of coma
- Ensuring the patient is normothermic, normotensive, and free of medications that can interfere with the neurologic examination and apnea testing, as recommended by the 2011 guidelines 1
- Performing a clinical examination showing:
- Coma with no response to stimuli
- Absent brainstem reflexes (pupillary, corneal, oculocephalic, oculovestibular, gag, cough)
- No spontaneous respirations on apnea testing, with documentation of an arterial Pa CO2 20 mm Hg above the baseline and ≥ 60 mm Hg with no respiratory effort during the testing period, as specified in the guidelines 1 Specific steps for determining brain death include:
- Treating and correcting hypotension, hypothermia, and metabolic disturbances before proceeding with the evaluations, as recommended by the guidelines 1
- Discontinuing medications that can interfere with the neurologic examination and apnea testing, allowing for adequate clearance before proceeding with these evaluations, as outlined in the guidelines 1
- Performing two examinations, including apnea testing, with each examination separated by an observation period, which may be 24 hours for term newborns (37 weeks gestational age) to 30 days of age, and 12 hours for infants and children (30 days to 18 years), as recommended by the guidelines 1
- Using ancillary studies, such as electroencephalogram and radionuclide cerebral blood flow, to assist in making the diagnosis of brain death, but not as a substitute for the neurologic examination, as specified in the guidelines 1 The diagnosis of brain death is confirmed when the above criteria are fulfilled, and death is declared, as outlined in the 2011 guidelines by the Pediatrics journal 1.
From the Research
Criteria for Determining Brain Death
The criteria for determining brain death in the Intensive Care Unit (ICU) involve a combination of clinical evaluation and ancillary tests. The American Academy of Neurology (AAN) has established guidelines that emphasize the following clinical findings to confirm brain death:
Clinical Evaluation
The clinical evaluation starts with determination of futility of any medical or surgical intervention and an unmistakable certainty that the underlying diagnosis is correct. The actual neurologic evaluation in a patient suspected of being brain dead requires a series of tests and verifications, including:
Ancillary Tests
Ancillary tests are needed when neurologic examination or apnea test cannot be performed. The AAN recommended ancillary tests include:
- Electroencephalogram (EEG)
- Catheter cerebral angiogram
- Transcranial Doppler
- Nuclear scintigraphy 2, 4 Digital subtraction angiography remains the gold standard for confirmation of lack of cerebral blood flow 2.
Imaging Studies
Imaging studies, such as computed tomography angiogram (CTA), MR angiogram, CT perfusion, and MR perfusion, are frequently used but are not currently recommended by AAN. However, they hold promise in future as imaging tools in the armamentarium of a radiologist investigating brain death as adjunct imaging to clinical findings 2, 4.
Role of Radiologist
A radiologist can play a critical role in recognizing the initial extensive hypoxic or ischemic damage to the central nervous system, including the brainstem on imaging, guiding a neurologist evaluating a potential brain death, and ruling out other pitfalls 2. The radiologist is often the first person to appreciate the devastating findings of irreversible brain damage.
Common Mimics of Brain Death
The three most common mimics of brain death are:
- Hypothermia
- Locked-in syndrome
- Drug intoxication 2