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Minimum criteria for the clinical diagnosis of brain death. An attempt at consensus. Part 2
The concepts of brain death or death by neurologic criteria (BD/DNC) were first proposed about 50 years ago. As the existing diagnostic criteria for BD/DNC differ across geographic areas, a consensus statement was developed by a multidisciplinary group of critical care, neurologic, and neurosurgical clinicians to harmonize the definition of BD/DNC.
While acknowledging lack of high-quality evidence, this document follows the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) methodology concepts and provides a distinction between strong recommendations 
, which according to the authors should be followed unless there is a compelling reason not to, and weak suggestions 
, where alternative courses of action may easily differ depending on patients, societal values, and available resources.
This is Part 2 of the recommendations. For Part 1, click here.
Ancillary testing in the diagnosis of BD/DNC
1. It is recommended that ancillary testing be performed in the following circumstances:
- Inability to complete the clinical examination, including the apnea test.
- Inability to exclude confounding conditions.
- Inability to interpret possible spinal movements.
2. It is recommended that the clinical examination be completed to the fullest extent possible prior to conducting an ancillary test.
Guidance concerning brain blood flow–based tests
1. Recommended tests include:
- Digital subtraction angiography or conventional cerebral angiography (which remains the gold standard).
- Radionuclide tests (angiography, perfusion scintigraphy) or transcranial Doppler ultrasonography in place of angiography (specialized requirements are suggested for all these tests, including previous evidence of flow on transcranial Doppler).
2. It is suggested that computed tomography angiography (CTA) and magnetic resonance angiography (MRA) not be used pending more data on their performance. It is also suggested that priority be given to further evaluation of those tests.
3. It is recommended that if the above recommended tests demonstrate blood flow, the diagnosis of BD/DNC cannot be made.
Guidance concerning electrophysiologic tests
1. It is suggested that electroencephalography (EEG) not be used as an ancillary test in adults unless mandated by local law or policy.
2. Given the limitations of EEG for evaluating brainstem, if performed as an ancillary test, EEG should be used in conjunction with somatosensory and brainstem auditory evoked potentials.
Additional recommendations concerning patients after treatment with targeted temperature management (TTM)
1. It is recommended that before the determination of BD/DNC neuroimaging be obtained to assess for both severe cerebral edema and brainstem herniation consistent with severe intracranial hypertension.
2. It is recommended that there should be a period of ≥24 hours after the temperature reaches 36 degrees Celsius before any determinations are attempted.
3. If central nervous system (CNS) depressing medications were recently administered, an ancillary brain blood flow study is recommended in addition to the clinical evaluation and apnea test to make a determination of BD/DNC. Waiting 5 half-lives and measuring drug levels is also recommended .
