E. Lee Murray, MD
CHAPTER CONTENTS
BRAIN DEATH
The Medical Consultants on the Diagnosis of Death to the President’s Commission for the Study of Ethical Problems in Medical and Biomedical and Behavioral Research published criteria for determination of brain death in 1981.1 Subsequent guidelines were published by the American Academy of Neurology in 1995,2 and further recommendations were published by Wijdicks in 2010.3 The criteria depend on absence of brain function, known cause, and irreversibility of the condition:
•Absence of all cerebral function
◦Coma with absence of response to any stimuli except spinal reflexes
•Absence of brainstem function
◦No signs of cranial nerve function including:
◦Negative cold caloric testing
◦No respiratory effort on apnea testing
•Irreversibility of the dysfunction
◦Known cause and not due to reversible etiology (e.g., intoxication)
◦Period of observation between two exams
◦Confirmatory test (e.g., electroencephalogram [EEG]) may be performed and shorten the required period of observation
Armed with criteria, the following list relates the procedures for establishing brain death:
•Steps for determination of brain death:
◦Establish irreversible and proximate cause of coma.
◦Achieve normal core temperature.
◦Achieve normal systolic blood pressure.
◦Perform a neurologic exam for brain death.
•Clinical examination for brain death:
◦No responsiveness: Including no eye opening or movement to noxious stimuli
◦Absence of brainstem reflexes: Pupil responses, oculocephalics, oculovestibular reflex, corneal reflex, facial movement to noxious stimuli, pharyngeal and tracheal reflexes
◦Apnea: Absence of breathing drive using standard procedures
◦Ancillary tests are performed especially if there is uncertainty about the reliability of parts of the neurologic exam or if apnea testing cannot be safely performed. Depending on protocols used, ancillary testing may reduce the period of observation before diagnosing brain death.
◦Preferred ancillary tests include EEG, radionucleotide flow study, and angiography.
Apnea testing is often performed by ventilating the patient with 100% O2 then disconnecting ventilatory support for several minutes. No respiratory effort despite a PaCO2 of at least 60 mm Hg is supportive of the diagnosis of brain death.
PERSISTENT VEGETATIVE STATE
Persistent vegetative state (PVS) is condition of unconsciousness while appearing awake. This can follow a variety of CNS insults including trauma, hypoxia, bilateral hemisphere damage from strokes, or encephalitis.4 PVS is defined as unconsciousness lasting at least 1 month from the onset, whether from a traumatic or nontraumatic cause (AAN 1995).5 Some investigators recommend longer times of observation, up to 3 months for nontrauma and 12 months for trauma patients.
The vegetative state can have some appearance of responsiveness, with roving eye movements, tearing, and grimacing to stimulation, but true cognitive response does not occur. EEG can show a variety of abnormalities, but typically does not show an alerting response to stimulation.
Families often have a particularly difficult time coping with and understanding the vegetative state. They frequently believe that there is more cognition than is present.
DIFFERENTIAL DIAGNOSIS
Differential diagnosis of brain death and persistent vegetative state is limited. Encephalopathy and other patterns of decreased response are seen commonly, but reversible causes resolve within hours to days, if addressed, and are not prominent in this differential diagnosis.
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