Brain Death

Complete and irreversible cessation of all brain function

Cause of coma must be established, compatible with a known cause of brain death

Reversible coma simulating brain death may be seen with

• Hypothermia (temperature < 32 °C)

• Overdosage with central nervous system depressant drugs

Hypothermia and drug overdose must be excluded by warming the patient and allowing enough time for all sedating medications to be metabolized (ie, at least 5 half-lives) or by measuring serum levels

Severe blood pressure, electrolyte, acid-base, and endocrine derangements cannot be present

Coma (irreversible)

No response to external stimulation

No brainstem reflexes

No spontaneous respirations and no respirations during apnea test

The apnea test (presence or absence of spontaneous respiratory activity at a PaCO₂ of at least 60 mm Hg or after a rise of 20 mm Hg from baseline) serves to determine whether the patient is capable of respiratory activity

An isoelectric electroencephalogram recorded according to the recommendations of the American Electroencephalographic Society may help in confirming the diagnosis

Alternatively, the demonstration of an absent cerebral circulation by intravenous radioisotope cerebral angiography or four-vessel contrast cerebral angiography is confirmatory

Palliative care