Diagnosing Brain Death

Death is a natural part of any trauma service due to the nature of the pathologies we see. At times, diagnosing “death” is cut and dry. But in some patients determining their status as “alive” or “dead” is not so straightforward and requires a more deliberate approach when evaluating them.

Brain death is not an uncommon diagnostic challenge in the Trauma ICU and is largely due to the nature of our patient population. There are no standards -- global or national -- for the diagnosis of brain death. Despite this lack of consensus regarding diagnostic criteria, there is relatively consistent belief about “brain death” across the nations, ethnicities, and religions -- that when a person is dead when that person's brain is dead, regardless of the status of other organs (2).

It helps to have a system to evaluate for brain death and we, like others, have our own institutional protocol to meet our own ethical and legal standards.

Regardless of institution or nation specific protocols, the goals for any brain death criteria are largely the same and include establishing an irreversible cause and absent cerebral AND brain stem function. In large part this means demonstrating:

1. IRREVERSIBLE insult

2. ABSENT brain stem reflexes

3. ABSENT spontaneous breathing

To meet the first goal, you must first exclude other confounding variables that could be contributing -- temperature should be at least 36.5 C, SBP > 90 mmHg, pCO2(arterial) ~ 40 mmHg and all electrolyte disturbances corrected, toxic/metabolic issues addressed.

After the confounders have been excluded and irreversibility is established, you can begin to assess for brain death. The ICU Book by Dr. Paul Marino is an excellent source in this regard, but to paraphrase, the assessment has four steps to it:

1. Ensure patient meets prerequisite physiologic parameters

2. Confirm absent brain function by observing an absence of reaction to pain

3. Confirm absent brainstem function by observing:

a. Non-reactive pupils

b. Absent corneal reflexes

c. Absent gag and cough reflexes

d. Absent oculocephalic and/or oculovestibular reflexes

4. Demonstrate lack of respiratory effort (“Apnea test”)

Meeting all of these criteria establishes the diagnosis of brain death and nothing further is needed. More often than not, however, the evaluation leads to equivocal or non-diagnostic results. In this case, confirmatory testing can be useful and includes cerebral angiography and EEG.

Brain death is a complex and evolving topic. Above are some general guidelines evaluating patients for brain death, and the pathophysiology of such findings are the sequelae of cellular death at the levels of the brain and brainstem. These findings should be routinely evaluated in any patient where brain death is a consideration and, when performed, should be done deliberately and carefully being sure not to miss fixable causes of the patients condition.

References

1. Marino P. The ICU Book. 3rd ed.

2. Wijdicks EFM. The Diagnosis of Brain Death. N Engl J Med. 2001;344(16):1215-1221.

3. Aminoff M. Clinical Neurology. 6th ed.

4. Wijdicks EFM. Brain death worldwide: Accepted fact but no global consensus in diagnostic criteria. Neurology. 2002;58(1):20-25.

Thanks to Dr. Allan Peetz for this post.