The concept that death can be diagnosed by neurologic as well
as cardiac criteria has been codified by law in the United States
in the Uniform Declaration of Death Act. Neurologic “brain” death
is particularly relevant to intensive care unit (ICU) care, where
cardiac and ventilatory function can be maintained in the absence
of brain function. Brain death is the primary requirement for organ
donation, although heart-beating and non–heart-beating
donors contribute to the donor organ pool. In adults, the primary
causes of brain death are traumatic brain injury and subarachnoid
hemorrhage, whereas pediatric donors are typically abuse victims.
Brain death was first defined in 1968 by an ad hoc committee at
the Harvard Medical School based on clinical criteria, and has subsequently
undergone redefinition by a variety of national and international
bodies. While the specifics vary, the requirements have in common
the requirements that the patient be in an irreversible coma, in
which the cause is known, the clinical examination is consistent
with brain stem death, confounding factors have been ruled out,
and confirmatory tests are consistent with the foregoing.
- ▪ Coma: A state of unconsciousness from which the patient
cannot be aroused even with stimulation such as pressure on the
supraorbital nerve, temporomandibular angle of the mandible, sternum,
- ▪ Irreversible coma: Coma wherein reversible causes such
as acid-base, electrolyte, endocrine disturbances, hypothermia (core
temperature < 32°C), drug intoxication,
hypotension, poisoning, and pharmacological neuromuscular blockade have
been ruled out as potential causes or contributors.
- ▪ Cause: Etiology of the coma.
- ▪ Brain stem examination: A series of tests in which the
function and reflexes of the mesencephalon, pons, and medulla oblongata
- ▪ Confirmatory tests: Radiologic and laboratory tests used
to confirm brain death, including cerebral angiography, electroencephalography,
transcranial Doppler ultrasonography, cerebral scintigraphy, as
well as serum drug levels.
- ▪ Clinical tests
- —Absence of motor responses to painful stimuli.
- —Absence of light reflex on pupillary examination
(no pupillary constriction to bright light) and pupils fixed in
midposition or dilated 4 to 9 mm in diameter (Figure 14-1).
- —Absence of doll’s eyes, that is, no compensatory
eye movement in response to rapid rotation of the head to either
- —Absence of oculovestibular response on cold-caloric
examination, wherein the tympanum is irrigated with ice water after
the head has been tilted to 30 (to make the auditory canal vertical
so that it will fill with cold water)—no eye deviation
toward cold stimulus (Figure 14-2).
- —Absence of corneal reflex, that is, no blinking
(Figure 14-3) when the cornea is touched (with a cotton swab or
- —Absence of gag reflex (Figure 14-4).
- —Absence of cough on suctioning or movement of the
- —Apnea test: Absence of spontaneous respiratory
effort in response to a Paco2 that is 60 mm Hg or 20 mm