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For further information, see CMDT Part 26-17: Stupor & Coma
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Complete and irreversible cessation of all brain function
Cause of coma must be established, be compatible with a known cause of brain death, and be irreversible
Reversible coma simulating brain death may be seen with
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 five half-lives) or by measuring serum drug levels
Severe blood pressure, electrolyte, acid-base, and endocrine derangements cannot be present
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The apnea test (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 that the patient is incapable of spontaneous respiratory activity
If an isoelectric electroencephalogram is recorded (according to the recommendations of the American Electroencephalographic Society), brain death should not be assumed unless brainstem auditory and somatosensory evoked potentials are also performed to assess brainstem function
The demonstration of an absent cerebral circulation by intravenous radioisotope cerebral angiography or four-vessel contrast cerebral angiography is confirmatory
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