Dying brain

Dying brain
Editor—Ancillary tests used to confirm clinically diagnosed
brain death may substantially influence the time of diagnosis,
as in the following case. A 48-yr-old woman was shot
to the head and was admitted to the hospital at 01:00
a.m. with a Glasgow Coma Scale (GCS) of 1 (eye), 5 (motor),
1 (verbal); brain tissue oxygen tension measured with an
intraparenchymal catheter was 12 mm Hg (normal range
15–35 mm Hg), and the intracranial pressure was 25 mm Hg.
At 07:00 a.m., GCS score was 3 with absent brainstem
reflexes. Brain CT revealed massive cerebral oedema, the
brain tissue oxygen tension was zero, and the intracranial
pressure was 81 mm Hg with a cerebral perfusion pressure
of zero. EEG showed a persistent low amplitude theta activity
at the vertex and transcranial Doppler (TCD) a persistent cerebral
blood flow in middle cerebral arteries (systolic flow velocity:
30 cm s–1) (Fig. 1A).
At 09:00 a.m. of the next day, EEG was flat, and the 6 h
observation period required by the Italian law to declare
brain death was started; however, a TCD still showed a very
low systolic flow velocity and a residual diastolic flow velocity
(Fig. 1B).
At 03:00 p.m., deep coma, absent reflex motor response
and brainstem reflexes, and flat EEG persisted. Brain death
was declared. TCD showed a reverberating flow indicating
cerebral circulatory arrest (Fig. 1C).
There is widespread acceptance of the concept of brain
death in the Western hemisphere,1 and a fairly uniform
agreement in Europe regarding the clinical criteria.2 There
is, however, considerable variation in the use of additional
confirmatory tests.1 2 These include flat EEG and determination
of cerebral circulatory arrest by means of cerebral
angiography, brain CT or MRI angiography, TCD, or cerebral
scintigraphy. In the UK,1 only clinical criteria are used and
brain death is defined as the complete, irreversible loss of
brainstem function. In Sweden,1 cerebral angiography is
the facultative ancillary test to confirm brain death; in
Italy, EEG is mandatory, while cerebral angiography, brain
CT angiography, TCD, or cerebral scintigraphy are all permitted
methods to document cerebral circulatory arrest in
children of ,1 yr of age, or if a complete and reliable clinical
evaluation is not possible.