Brain death and persistent vegetative states.

Patients who suffer severe brain damage may be brain dead, even though their cardiorespiratory function is supported by mechanical ventilation. According to criteria established in the United Kingdom and the United States, if these patients meet the preconditions of apneic coma that is attributable to diagnosed irreversible cause, and the presence of drug intoxication, hypothermia, or metabolic coma is excluded, then documentation of absent brainstem reflexes and apnea despite a PaCO2 of 50 mm Hg or greater will confirm the presence of brain death. If the brain is dead, the patient is dead, regardless of the state of his circulation, and he should be declared dead and removed from the ventilator. If the patient has lost higher cortical function but brainstem function is preserved, he may be in the persistent vegetative state and live for years with apparent sleep-wake cycles but no awareness of any external or internal stimuli. As the prognosis for recovery from the persistent vegetative state is absent, there is no ethical responsibility to continue treatment other than to provide basic nursing care to maintain the dignity of the patient.