Transcript Online Module: Brain Death Brain Death

Online Module:
Brain Death
Brain Death
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Brain Death is “irreversible cessation of brain
and brainstem function.”
In Louisiana, any MD can pronounce a patient
“brain dead,” although different institutions
have different rules and regulations regarding
this (for example, at LSU interim hospital it
must be a chief resident or faculty physician).
Criteria for determination of Brain
Death
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Absent cerebral and brainstem function
Well-defined etiology that is irreversible
Persistent absence of all brain and brainstem
function after observation and/or treatment
Hypothermia, intoxication, metabolic
encephalopathy, shock, and/or other reversible
factors that can confound the assessment are
excluded, corrected, and/or absent.
In other words…
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There must be a known and sufficient etiology
to account for the patient’s condition.
All reversible causes of brainstem dysfunction
must have been excluded.
The passage of sufficient time to demonstrate
irreversibility.
The failure of all relevant therapeutic measures
to reverse the condition.
Don’t “D’oh!”
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A patient under anesthesia IS NOT BRAIN
DEAD!!! Nor can you call an intoxicated
patient brain dead (even though he/she may be),
or a patient that has a core body temperature
less than 90 degrees F, etc., etc., etc.
Less than two years ago, a Louisiana resident
MD declared a patient “brain dead” who literally
walked out of the hospital two days later.
Clinical Brain Death
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Cerebral unresponsiveness
No spontaneous motor activity
Absent brainstem reflexes
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Papillary, corneal, oculocephalic, etc.
Absent cough/gag reflex with deep endotracheal
suctioning
Absent respiratory drive to hypercarbia
(PaCO2>60)
Confirmatory tests
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EEG
Radionuleotide angiography
Contrast cerebral angiography
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…or any radiographical method that assesses
intracerebral blood flow
Others exist…
Confirmatory tests
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Key to understand is that none of these
“confirmatory tests” is sufficient, in and of
itself, to diagnose brain death. They are merely
adjuncts. First, you must have a clinical exam
consistent with brain death.
Confirmatory tests
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A silent EEG, for example, can be consistent
with brain death. It can also be consistent with
pharmacological influence (i.e., anesthesia) or
drug intoxication.
By contrast, EEGs don’t always “confirm” brain
death.
There can be minor transient EEG activity even in
the setting of clinical brain death.
 Electrical artifacts on EEG in the ICU setting have
been described.
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Important point
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The most important thing to understand is that
a good clinical examination is the foundation of
an accurate brain death determination.
Confirmatory tests are utilized on a case by case
basis for a variety of reasons, but are
nevertheless not the cornerstone of brain death
determination.
Moving to the clinical
exam…
Clinical Evaluation:
Unresponsiveness
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The patient must demonstrate no response to
any stimulation.
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Spontaneous movement is almost always absent.
Seizures, shivering, any posturing, etc., indicates
brainstem function and is not consistent with
the determination of brain death.
The presence of spinal reflexes does not exclude
brain death, but if there is any doubt then the
diagnosis of brain death should be withheld.
Brainstem Reflexes: Pupils
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The pupils must be unreactive to light (note:
they do NOT have to be dilated) in the absence
of confounding variables (i.e. cateracts,
significant ocular/orbital trauma,
pharmacological effects, etc.).
Any pupil movement in response to light is
inconsistent with diagnosis of brain death.
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Review the light reflex pathway, in case you get
asked! 
Brainstem Reflexes: Pupils
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Shine a light directly into each eye individually,
observing the direct response of the pupil as
well as the consensual response of the other
pupil.
In the ER or ICU setting (i.e. a comatose
patient), it sometimes helps to dim the lights of
the room, or turn them out entirely during the
exam, to increase the contrast and be sure that
there is no light response.
Brainstem Reflexes: Corneals
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The corneal reflex has an afferent and efferent
component as well.
The afferent limb is carried by branches of the 5th
cranial nerve, which carries sensation from the
cornea back towards the brain/brainstem.
 The efferent limb is carried by the 7th cranial nerve,
which directs the eyelid “blink” in response to the
stimulus.
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Its presence, even if only on one side, is not
consistent with diagnosis of brain death.
Brainstem Reflexes: Corneals
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In the ER or ICU setting, you may need to hold
the eyelid(s) open.
Use a small piece of cotton, the corner of a 2x2,
etc., and gently touch the cornea (repeat for
other eye).
Look very closely for any response (sometimes it is
very subtle).
 Avoid touching the eyelashes, as you may
inadvertently move the lid and think you’ve seen a
response when there was none.
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Brainstem Reflex: Doll’s Eye
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The Oculocephalic, or “Doll’s Eye” reflex, is
mediated by unconscious brainstem pathways
that work to keep your eyes focused on a point
or target during movement of your head.
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The easiest way to think about it is this: When your
head moves one way, your CNS produces eye
movement in the opposite direction in order to keep
whatever image you’re viewing “locked in place” on
the retina.
Brainstem Reflexes: Doll’s Eye
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To check the Oculocephalic reflex, turn the
patient’s head rapidly to one side and check to
see if the eyes move in response.
For example, if you check a patient with a
NORMAL Doll’s Eye reflex who is laying on a
stretcher and staring at the ceiling, turning the
patient’s head to the left should cause the
patient’s eyes to look to the right in an attempt
to remain focused on the ceiling.
Brainstem Reflexes: Doll’s Eye
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Note: This test should be avoided in the setting
of a patient with questionable stability of the
cervical spine (i.e. in a trauma setting where
cervical spine injury has not yet been ruled out).
Brainstem Reflexes: Cold Calorics
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The oculovestibular reflex (i.e., “cold calorics”)
is an excellent tool to assess the vestibular
pathways in a patient with an uncleared cervical
spine.
This is performed by injecting cold water into
the ear canal(s) for 20-30 seconds.
Cold Calorics
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The head of the patient should be elevated to
~30 degrees.
Infuse cold water into each ear canal separately
for 20-30 seconds, observing the eyes for any
response both during and immediately after the
infusion of water.
Any ocular movement in response to this test
indicates residual brainstem function, and is
inconsistent with brain death.
Cold Calorics
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Note: This test should be avoided in the setting
of a patient with possible CSF leak (i.e. a trauma
setting where a patient has sustained a
significant traumatic brain injury and there is
blood/fluid leaking out of one or both ears).
Brainstem reflexes: Cough/Gag
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Deep endotracheal suctioning and gentle
manipulation (without dislodging it or changing
its position) of the endotracheal tube are good
ways to evaluate a patient’s cough/gag reflex.
Presence of the cough and/or gag reflexes
indicates persistence of the glossopharyngeal
and vagal systems and is inconsistent with the
diagnosis of brain death.
Apnea Test
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The Apnea Test has become a key component in
the determination of brain death.
Understand: If ANY prior component of your
clinical exam is inconsistent with brain death
and/or any criteria for determination of brain
death is not met, it is inappropriate to perform
an Apnea Test.
Thus, the Apnea Test is often the “last straw” in
the clinical determination of brain death.
Apnea Test
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The logic of the Apnea Test is based upon
hypercarbia being a significant driving force for
respiration.
Thus, in the presence of significant hypercarbia
( > 60 mm Hg), if there is absence of
respiratory effort, a diagnosis of brain death is
supported.
Apnea Test
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According to the American Academy of
Neurology, the following represents the
recommended protocol for performing an apnea
test…
Apnea Test
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Prerequisites
Normal core body temperature
 Systolic Blood Pressure > 90
 Normal PaCO2 (~35-45 mm Hg)
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So, draw ABG right before starting the test.
Absence of any other underlying conditions that
could confound diagnosis by mimicing brain death
or suppressing respiratory drive
Performing the Apnea Test
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Pre-oxygenate with 100% Oxygen for 30 min.
Connect a pulse-ox, then disconnect ventilator.
Place a nasal cannula at the level of the carina;
give 100% Oxygen at 8L/min. during test.
Watch closely for respiratory movements (any
abdominal or chest movement that represents
respiratory effort)
Draw ABG ~10 minutes and reconnect
ventilator.
Interpreting the test
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The apnea test is POSITIVE (i.e., supports the
diagnosis of brain death) if:
There are no respiratory efforts during the test
AND
 Repeat ABG shows PCO2 > 60 mm Hg.
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Interpreting the test
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The apnea test is INDETERMINATE if:
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after 10 minutes, the patient demonstrates no
respiratory effort, but the PCO2 is < 60 mm Hg.
The apnea test is NEGATIVE (i.e., does NOT
support the diagnosis of brain death) if:
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the patient demonstrates any respiratory effort at any
time during the test.
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Cease the test and reconnect the ventilator immediately
upon observing respiratory effort.
The Apnea Test
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If the patient becomes unstable at any point
during the Apnea Test (i.e. SBP drops less than
90, significant desaturation on pulse-oximetry,
observance of cardiac arrhythmias, etc.), the test
should be aborted.
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The Apnea Test should not “induce a code!”
Final Thought
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Remember that the clinical exam is the
cornerstone of brain death determination, and
there is no test or substitute for an examiner’s
judgment and skills.