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For further information, see CMDT Part 24-17: Stupor & Coma

Key Features

  • 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

Clinical Findings

  • 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

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