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CHAPTER 88: Coma, Persistent Vegetative State, and Brain Death 839

has been documented. The successful performance of an apnea test many of the problems associated with EEG and cerebral angiography.
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requires a specific methodology to minimize hypoxemia during testing Unfortunately, the technique is only available in referral centers.
and proactively manage hypotension to ensure study completion. For Absence of any electrical activity on a 30-minute EEG with increased
these reasons, it should only be done by physicians experienced with the sensitivity settings is consistent with brain death and has a reported
test. Generally, inability to adequately perform an apnea test (eg, because sensitivity and specificity of about 90%. If the cause of coma is clearly
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of hypotension or a marked drop in oxygenation) should indicate the established from anatomic imaging studies of the brain, and clinical cri-
need for a confirmatory test. teria are met that all brain functions are absent, EEG confirmation is not
In the previous AAN practice parameter from 1995, two physicians necessary. Apneic coma and an isoelectric EEG in the face of normal
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were required to perform and document a neurological examination brain imaging studies are strongly suggestive of sedative drug intoxica-
along with one apnea test, to declare a patient dead by brain death cri- tion, and appropriate toxicology studies must be performed.
teria. No instance has been reported wherein a patient has recovered
brain function when testing has been performed in accordance to the ■ NEUROLOGIC STATES RESEMBLING BRAIN DEATH
AAN practice parameter. Therefore, the guidelines for diagnosis of A correct identification and verification of brain death is rather dif-
brain death have been recently updated. Only one clinician is now ficult and complex and misjudgment may have great negative impact,
required to perform a neurological examination and apnea test to not only on the patient, but also on the family and the diagnosing
diagnose and declare a patient dead using brain death criteria. 65 medical doctor. The diagnosis should only be made by a physician with
Certain spinal movements and reflexes can be observed in brain-dead experience in careful neurologic examinations, interpretations of brain
patients without casting doubt on the diagnosis. They may be especially imaging studies, and skilled evaluation of confirmatory studies used to
prominent during apnea testing, and physical stimulation of the patient. diagnose brain death. Misleading diagnoses may lead the superficial
They are often short lasting and symmetric. Well known but rather examiner to believe that the patient is brain dead, but often the history
uncommon in its complete form is a brief attempt of the body to sit up and examination together reveal details inconsistent with the diagnosis
to about 60° with raising of both arms (Lazarus sign). A convenient clas- of cerebral perfusion arrest. For details, the reader is referred to current
sification of spinal movements and reflexes seen in brain-dead patients textbooks in neurology and a monograph by Wijdicks. Examples of
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by body region includes but is not limited to cervical region (tonic neck disorders potentially mimicking brain death include but are not limited
reflexes or head turning), upper extremities (flexion-withdrawal or to severe hypothermia, acute metabolic coma (eg, endocrine and organ
extension pronation or flexion), trunk (opisthotonic posturing, flexion, failure, among others); poisoning (via drugs such as antidepressants,
or abdominal reflexes), and lower extremities (plantar flexion, triple anticonvulsants, analgesics/sedatives, and many more, or via toxins and
flexion, or Babinski sign). Observation of any of these movements poisons); locked-in syndrome, akinetic mutism, and possible PVS, as
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should lead to verification that they are compatible with the diagnosis of well as peripheral nerve disorders in which the patient may appear brain
brain death (by an experienced physician) and preparation of the family dead, but is fully awake.
of their mechanism and relevance.
■ CONFIRMATORY TESTING CRITICAL CARE ASPECTS OF BRAIN-DEAD PATIENTS

Generally, confirmatory testing is recommended in children less than It is well known that brain injury can have immediate and delayed
1 year old and in situations in which adequate clinical testing cannot systemic effects on multiple organs. Hence, it is not surprising that
be performed. Lack of cerebral blood flow, that is, cerebral circulatory brain-dead patients will experience significant effects on overall body
arrest, can be documented by standard arterial angiography, transcranial function. Generally, vascular motor tone and cardiac stability and
Doppler, or radionuclide scan, and there is some, but limited, experience performance decreases, pulmonary edema, disseminated intravascular
with magnetic resonance imaging/angiography and CT angiography. coagulation, and hypothermia may occur, and severe electrolyte and
Four-vessel cerebral angiography may be performed in clinically dead fluid balance disturbances are noted. Up to one-quarter of all potential
patients who have an uncertain diagnosis. Complete absence of cere- donor organs are rejected because of the detrimental impact of these
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bral circulation is an absolute confirmation of brain death. The major changes, which are commonly associated with inadequate medical man-
use of the technique is for rapid diagnosis of death in patients whose agement (see Chap. 115).
clinical examination is obscured by hypothermia or drug intoxication. Determining a brain-dead patient as a medically suitable organ
Transcranial Doppler sonography is a noninvasive bedside technique donor is only done by organ procurement organizations. All brain-dead
that can measure, in a qualitative fashion, blood flow in the proximal patients should be managed as potential organ donors. The support of
portions of the main cerebral arteries. An ultrasonic probe is placed over a patient who has been declared dead after brain testing poses a moral
the temporal bones (usually) and the direction and velocity of blood flow dilemma for the attending physician. Unless there are explicit wishes to
can be measured. A number of investigators have shown that absence or this end by either patient statements or family requests, the caring physi-
reversal of diastolic flow in the cerebral arteries can be demonstrated in cian cannot continue to support the body for the purpose of assessment
patients who meet the traditional criteria for brain death ; the operator- by organ procurement agencies. It is therefore imperative to involve
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dependent sensitivity ranges from 90% to 99%, and the specificity is them early. However, should the decided course be to pursue organ
100%. About 10% of patients cannot be insonated because of excessive retrieval the following issues need to be addressed:
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skull thickness. Radioisotope brain scanning can accurately document
absent brain blood flow in the cerebral hemispheres, but not in the verte- 1. Maintain hemodynamic stability: The initial response of brain
brobasilar circulation. Some institutions have portable units that can be injury is massive discharge of catecholamines leading to hyperten-
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brought to the bedside in the ICU. Because this technique does not image sion and tachycardia and not infrequently myocardial injury. In
the posterior circulation, the clinical diagnosis of brain stem areflexia brain death, hypotension and hypovolemia associated with elec-
becomes even more important. In situations of suspected or known drug trolyte and temperature disturbances will lead to systemic vascular
intoxication, isotope brain scanning is not helpful, since it will not answer instability. Target hemodynamic goals in these patients could be
the question of whether brain stem areflexia is due to drug effect or irre- simplified to maintain systolic blood pressure at about 100 mm Hg,
versible damage. Xenon-enhanced CT and 99m T-HMPAO single photon heart rate <100 beats per minute, and urine output >100 mL/h.
emission computed tomography (SPECT) are noninvasive techniques For fluid resuscitation, boluses of either 5% albumin or crystalloid
for accurately measuring brain blood flow in all arterial territories. It has infusion are recommended; the particular choice depends on the
been used in young children and infants with great reliability to confirm treating physician’s preference and individual patient’s sensitivity
the clinical criteria of death. Particularly in children, it can overcome to low osmotic pressure–mediated tissue edema. For heart-lung
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