What are the criteria to confirm brainstem death (brain death)?

From the Guidelines

Brain stem death is confirmed through a series of specific clinical tests performed by two experienced clinicians on two separate occasions, with a minimum observation period of 24 hours for term newborns and 12 hours for infants and children, as recommended by the American Academy of Pediatrics 1. To confirm brain stem death, the following prerequisites must be met:

• The patient must have an irreversible brain injury of known cause
• The patient must be in a coma with no response to stimuli
• The patient must require mechanical ventilation
• There must be no confounding factors like hypothermia (temperature >36°C), severe metabolic or endocrine disturbances, or sedative drugs in their system The clinical tests include:
• Checking for absent brain stem reflexes: no pupillary response to light, absent corneal reflexes, no eye movement to caloric testing (cold water in ear canal), no gag or cough reflexes when the trachea is stimulated, and no motor response to pain in areas supplied by cranial nerves
• The apnea test, where the patient is disconnected from the ventilator while maintaining oxygenation, and observed for a period to confirm no spontaneous breathing despite rising CO2 levels (PaCO2 ≥ 60 mmHg) 1
• Ancillary tests like EEG or radionuclide cerebral blood flow may be used in situations where clinical testing cannot be completed, but are not required to establish brain death unless the clinical examination or apnea test cannot be completed 1 The diagnosis of brain death should be made by physicians who have evaluated the history and completed the neurologic examinations, and death is declared after confirmation and completion of the second clinical examination and apnea test 1. Key considerations in the diagnosis of brain death include:
• The importance of correcting hypotension, hypothermia, and metabolic disturbances before initiating brain death evaluation 1
• The need to discontinue sedatives, analgesics, neuromuscular blockers, and anticonvulsant agents for a reasonable time period before examination for brain death 1
• The use of ancillary studies to assist in making the diagnosis of brain death, particularly in situations where clinical testing cannot be completed or there is uncertainty about the results of the neurologic examination 1

From the Research

Confirming Brain Stem Death

To confirm brain stem death, the following steps can be taken:

• Clinical criteria set by the American Academy of Neurology (AAN) emphasize 3 specific clinical findings to confirm brain death, which include coma, absence of brainstem reflexes, and apnea 2.
• Ancillary tests are needed when neurologic examination or apnea test cannot be performed, such as electroencephalogram, catheter cerebral angiogram, transcranial Doppler, and nuclear scintigraphy 2.
• Digital subtraction angiography remains the gold standard for confirmation of lack of cerebral blood flow 2.
• Imaging markers for brain death on computed tomography angiogram (CTA) include nonopacification of the cortical middle cerebral arteries and internal cerebral veins 2.
• On magnetic resonance imaging, there can be massive brain edema with herniations, poor gray or white matter differentiation, diffuse diffusion restriction, and nonvisualization of intracranial vessels on MR angiogram 2.

Ancillary Tests

Ancillary tests can aid in the declaration of brain death, including:

• Electroencephalogram (EEG) to confirm electrical activity loss 2, 3.
• Evoked potentials, such as somatosensory evoked potential and brainstem auditory evoked potential, to support the clinical diagnosis of brain death 3.
• Catheter cerebral angiogram to confirm loss of cerebral blood flow 2.
• Transcranial Doppler to indicate cerebral circulatory arrest 2.
• Nuclear scintigraphy, such as 99m Techentium hexa methyl propylene amine oxime or 99mTechnetium-ethylene cysteine diethyl ester, to confirm lack of intracranial radiotracer uptake 2.

Clinical Scenarios

Ancillary tests may be particularly useful in certain clinical scenarios, including:

• Equivocal results of clinical examination findings 3.
• Inability to perform some aspects of the neurologic examination 3.
• Concern for residual sedative effects 3.
• Suspected spinal cord or neuromuscular injury 3.
• Posterior fossa lesions with brainstem involvement 3, 4.

Scoring Systems

Scoring systems, such as the Full Outline of Unresponsiveness (FOUR) score and the Glasgow Coma Scale (GCS), can be used to evaluate the level of consciousness and predict brain death 5, 6.

• The FOUR score and GCS had 100% sensitivity and low specificity in predicting brain death 5.
• The combination of clinical and neurophysiological data, such as the trigeminal-auditory Glasgow (Coma Scale) score (TAG score), can improve the evaluation of deep comatose patients and assist in the management of such patients 6.