How is Brain Death Defined?

Ethical and Legal Concerns Surrounding Cessation of Life Support

May 15, 2009 Stephen Allen Christensen

Although brain death implies the absence of brainstem reflexes, spinal reflexes may remain. This persistent "response" may confuse family members.

The declaration of clinical death prior to termination of life support or harvesting of organs has become more challenging due to improvements in technology that perpetuate cardiopulmonary function.

It is now widely accepted both culturally and legally that a person’s death is signified by the irreversible cessation of all meaningful brain activity—including that of the brainstem.

However, in spite of Hollywood’s portrayal of end-of-life scenarios, simply obtaining a “flatline” electroencephalogram (EEG) is not sufficient for determining brain death. Indeed, an EEG is not even a necessary part of the decision-making process.

Cardinal Signs of Brain Death

Before a physician can declare that an individual is brain dead, several basic criteria must be met:

• The patient must be comatose or unresponsive
• Cerebral responses to pain must be absent in all extremities
• Brainstem reflexes must be absent
• The patient must be apneic (i.e., incapable of initiating spontaneous respiratory activity)
• (Note that spinal reflexes may persist, allowing continued withdrawal motions)

Furthermore, the diagnosis of brain death cannot be confidently made unless the following requirements are fulfilled:

• Clinical or neuroimaging evidence (i.e., CT, MRI, etc.) must indicate the occurrence of a cerebral event that is consistent with the diagnosis of brain death
• Conditions that may mimic brain death or interfere with proper diagnosis (e.g., acute metabolic or endocrine syndromes) must be excluded
• Drug intoxication or poisoning must be ruled out
• The patient must not be hypothermic (i.e., core body temperature must be ≥32º C [90º F])

(From Sullivan J, et al. Determining brain death. Critical Care Nurse. 1999;19(2):37-46)

Since a declaration of brain death is not an inconsequential one, physicians must adhere to standards that have been reviewed and repeatedly substantiated over the years. Variations in state laws or institutional policies - in addition to specific clinical settings - may prompt adaptations in the application of these guidelines.

Guidelines for Determining Brain Death

(All criteria must be fulfilled to declare brain death)

1. All reasonable efforts were made to notify next of kin or other appropriate persons.
2. Cause of the coma is known; said cause must be sufficient to account for irreversible loss of brain function.
3. Drugs, hypothermia, and extremely low blood pressure have been excluded as causes of depressed brain function.
4. Observed movements, if any, can only be attributed to spinal cord function (i.e., they cannot be due to cerebral or brainstem activity)
5. Corneal and papillary light reflexes are absent.
6. Cough and pharyngeal reflexes are absent.
7. Oculomotor and caloric responses (eye motion in response to head movement and stimulation of eardrums) are absent.
8. The patient demonstrates no spontaneous respiratory activity in response to an eight-minute apnea test.
9. At least one of the following four criteria must be fulfilled:

• Items 2-8 have been confirmed by repeat examinations separated by at least six hours.
• Items 2-8 have been confirmed AND an EEG shows electrocortical silence; a second examination reconfirms items 2-8 at least two hours after the first examination.
• Items 2-8 have been confirmed AND arteriography reveals no blood flow to the brain; items 2-8 are reconfirmed at least two hours after the first examination.
• If any of items 2-8 cannot be confirmed because injury or the patient’s condition prohibits testing, all items that are assessable must be confirmed, arteriography must reveal no intracranial blood flow, and a second examination at least six hours after the first reconfirms the initial evaluation.

Although current criteria for the declaration of brain death are supported by rigorous research and a high degree of clinical certainty, the concept of brain death remains a topic of debate among clinicians and ethicists.

The copyright of the article How is Brain Death Defined? in General Medicine is owned by Stephen Allen Christensen. Permission to republish How is Brain Death Defined? in print or online must be granted by the author in writing.

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