Page 1201 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

838 PART 6: Neurologic Disorders

Other than general measures, as outlined above, treatment depends on beliefs and laws. It is unlikely that there will ever be a unanimously
accurate diagnosis of cause and specific directed treatment. accepted definition of death, due to diverse religious and ethical
opinions. However, time has brought about increasing acceptance that
the irreversible cessation of brain function is a mechanism of death.
PROGNOSIS AND THE PERSISTENT VEGETATIVE STATE The core of the clinical diagnosis of brain death is to establish unre-
While it is possible to describe broad prognostic likelihoods for patients sponsiveness and brain stem areflexia. The preconditions are that (1) the
with nontraumatic coma, particularly postanoxic brain injury (see cause of coma is known and (2) the cause is adequate to explain the irre-
above), there are no precise tools to determine which patients with versible cessation of whole brain function. 60,61 In almost all cases, cerebral
coma will evolve to vegetative state. Generally, the clinical course and circulatory arrest from intracranial hypertension is the terminal mecha-
long-term outcome of vegetative state depend in part on the etiology nism. Confirmatory tests are appropriate in selected cases, particularly for
of the brain injury. A useful classification in this regard describes three posterior fossa processes that can cause devastating brainstem dysfunc-
broad categories: (1) acute traumatic and nontraumatic brain injuries, tion without hemispheric injury. Careful attention to these preconditions
(2) degenerative and metabolic brain disorders, and (3) severe con- will alert the intensivist to special circumstances that require reevaluation
genital malformations of the CNS. Recovery of consciousness from a and confirmatory tests. In the press for organ procurement, the cautious
posttraumatic PVS is unlikely after 12 months for both children and physician may be perceived as delaying the transplant process to ensure
adults. For nontraumatic PVS, recovery after 3 months is exceedingly that the diagnosis of death is unequivocal.
rare. Patients with degenerative disorders or congenital abnormalities The President’s Commission’s recommendations grew out of studies
are very unlikely to recover consciousness after several months of PVS. at Harvard Medical School in the 1960s and extensive collaborative
For all atraumatic patients remaining in PVS, life span is substantially studies sponsored by the National Institute of Neurological Disorders
reduced and generally ranges from 2 to 5 years. However, life expec- and Stroke in the years 1971 and 1972. 62,63 These clinical studies were
tancy after severe TBI producing coma is 8 to 12 years. Life expectancy performed before the availability of CT imaging, making the cause of
is largely influenced by the complications accompanying chronic care of coma and anatomic extent of brain damage uncertain in many cases.
these individuals. Therefore, the use of routine EEG became a standard part of many
Only about half of all patients with full-time employment prior to the determination-of-death protocols. With the ability to directly visualize
severe head injury event were able to return to full time employment, the extent of brain damage in comatose patients by CT, the determina-
50
most of them at lower occupational status. In a group of severely brain- tion of irreversibility became more precise. To this day, however, there
injured young men, however, the reemployment rate can be significantly continues to be unnecessary reliance on confirmatory laboratory tests
improved by using on-site training accompanied by a job coach, as well rather than the use of objective clinical criteria. In contemporary prac-
as continuing long-term support with use of behavioral and cognitive tice, the use of transcranial Doppler to verify cerebral circulatory arrest
training strategies. 51,52 is more relevant than EEG.
In most states in the United States and many countries around the
■ DECLARATION OF DEATH USING NEUROLOGIC CRITERIA world, clinical criteria are sufficient to diagnose brain death. Confirmatory
tests are reserved for situations in which there is uncertainty regarding
In recent years, the success rate of organ transplantation has increased cause and reversibility of coma, or if a complete neurological examination
dramatically, and transplantation has become standard therapy cannot be performed. This may arise in instances of facial trauma and
for patients with end-stage kidney, heart, lung, and liver disease. hemodynamic instability, which precludes apnea testing.
organs due to a lack of understanding of the concepts and criteria for ■ CLINICAL DIAGNOSIS
Unfortunately, thousands of critically ill patients will not receive needed
the declaration of death. We are wasting a rare and precious resource It is important to keep a structured approach in mind when approach-
because health professionals, as well as the public, have been misin- ing a patient with the possible diagnosis of brain death. First, imperative
formed about definitions and procedures necessary to declare death in prerequisites that should be fulfilled prior to determination of brain
the setting of massive, irreversible brain damage. 53,54 death include (1) irreversible brain catastrophe, which involves both the
Although specific protocols for the determination of death vary cerebral hemispheres and the brain stem; (2) core temperature >36°C;
slightly from institution to institution, guidelines in the United States (3) no evidence of intoxication, poisoning, or the use of paralytics,
were firmly established by the President’s Commission in 1981 and anesthetics, or sedatives; (4) normotension (systolic BP >100 mm Hg);
have been uniformly accepted by the American Medical Association, and (5) no confounding medical conditions such as severe endocrine,
American Academy of Neurology, and American Bar Association. 55-57 electrolyte, and acid-base disturbances. CT scan may or may not show
The Uniform Determination of Death Act states, “An individual who abnormalities consistent with brain death. For example, following car-
has sustained either (1) irreversible cessation of circulatory and respira- diopulmonary arrest the CT may show abnormalities only visible to the
tory functions, or (2) irreversible cessation of all functions of the entire expert and may be interpreted as normal by those who are less expe-
brain, including the brain stem, is dead. A determination of death must rienced. On the other hand, a significant and easily identifiable mass
be made in accordance with accepted medical standards.” In 1987, the lesion seen on CT scan does not necessary imply brain death. As a rule,
state of New York adopted the preceding statement as the legal defini- if the brain CT is discrepant with the clinical diagnosis of brain death, a
tion of death. Since that time, this definition has been widely adopted repeat study is warranted; if the repeat CT scan remains discrepant, the
throughout North America and Europe. 58,59 search for other confounding factors should be intensified.
However, confusion still surrounds (1) the definition of death and The examination of a neurologically devastated and potentially
(2) the criteria for determining death in a patient who has stable car- brain-dead patient should be methodologic as well as documented in
diovascular function but irreversible cessation of brain function. Part detail: Identify the lack of consciousness (coma), verify the patient’s core
of this confusion arises from the continued use of the ambiguous term temperature and ventilator dependency, test and describe that no motor
brain death, implying that there is more than one type of death. If health movements and no brain stem reflexes are present (including pharyn-
professionals are confused about this concept, it is no surprise that the geal and tracheal reflexes), and demonstrate the lack of spontaneous
public remains uncertain about the terminology. respiration to increasing arterial carbon dioxide levels (apnea test). The
The medical and legal definitions of death are clear: Brain death apnea test demonstrates the lack of respiratory drive while the patient
and cardiac death are the same. Dissenting opinions from the religious remains oxygenated; a patient fails the apnea test when an increase
orthodoxy of Roman Catholicism and Orthodox Judaism persist, how- of arterial CO to 60 mm Hg (from a baseline range of 35-45 mm Hg)
2
ever, due to individual interpretations and applications of religious or a 20 mm Hg increase from the pre-apnea test baseline arterial CO
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