From the Guidelines
Brain death is determined by a clinical diagnosis based on the absence of neurologic function with a known irreversible cause of coma, and requires two examinations, including apnea testing, separated by an observation period, as recommended by the American Academy of Pediatrics 1. The criteria for determining brain death include:
- A known cause of brain injury
- Normothermia (temperature >36°C)
- Normal blood pressure (systolic >100 mmHg)
- Absence of confounding factors like sedatives, paralytics, metabolic disorders, or severe acid-base disturbances
- Coma with absence of all brainstem reflexes:
- No pupillary response to light
- No corneal reflexes
- No oculocephalic (doll's eyes) or oculovestibular (cold caloric) reflexes
- No gag or cough reflexes
- No motor response to pain in any cranial nerve distribution
- Apnea testing, performed by pre-oxygenating the patient, disconnecting from the ventilator while providing oxygen, and observing for a period to confirm no respiratory effort despite PaCO2 rising above 60 mmHg
- Two examinations, including apnea testing, separated by an observation period:
- 24 hours for term newborns (37 weeks gestation to 30 days of age)
- 12 hours for infants and children (31 days to 18 years) The examination should be performed by different attending physicians, and the apnea test may be performed by the same physician. Ancillary studies, such as electroencephalography, cerebral angiography, transcranial Doppler, or nuclear medicine perfusion scans, may be used to assist in the diagnosis of brain death, but are not required unless the clinical examination or apnea test cannot be completed safely. The determination of brain death requires a systematic and thorough approach to ensure accuracy and avoid conflicts of interest 1.
From the Research
Criteria for Determining Brain Death
The criteria for determining brain death include:
- Clinical diagnosis characterized by the irreversible loss of neurologic function caused by global injury to the brain, including the brain stem 2
- Irreversible cessation of functioning of the entire brain, including the brainstem 3
- Coma, absence of brainstem reflexes, and apnea 4, 5
- Absence of cerebral electrical activity and cerebral circulatory arrest 3
Ancillary Tests
Ancillary tests used to confirm brain death include:
- Electroencephalography (EEG) to confirm electrical activity loss 4, 5
- Catheter cerebral angiogram to confirm loss of cerebral blood flow 4, 5
- Transcranial Doppler to confirm cerebral circulatory arrest 4, 5
- Nuclear scintigraphy to confirm lack of intracranial radiotracer uptake 5
- CT angiography, MR angiography, CT perfusion, and MR perfusion to demonstrate absence of cerebral blood flow and electrical activity 2, 3, 5, 6
Imaging Findings
Imaging findings that suggest brain death include:
- Nonopacification of the cortical middle cerebral arteries and internal cerebral veins on CT angiography 5
- Lack of cerebral blood flow and blood volume in brainstem on CT perfusion 5
- Massive brain edema with herniations, poor gray or white matter differentiation, diffuse diffusion restriction, and nonvisualization of intracranial vessels on MR angiogram 5
- Flow patterns without forward flow progress on transcranial Doppler 5