Page 1192 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 88: Coma, Persistent Vegetative State, and Brain Death 829

CHAPTER Coma, Persistent Vegetative TABLE 88-1 Clinical levels of Altered Consciousness
88 State, and Brain Death Terms Eyes Arousability Content
Mildly impaired
Lethargy
Closed Arousable
Halinder S. Mangat
Axel Rosengart Stupor Closed Arousable with effort Markedly impaired
Coma Closed Unarousable Not applicable
Akinetic mutism (abulic state, coma vigil) Open Wakeful Impaired
a
KEY POINTS
Locked-in syndrome b Open Wakeful Normal
• The neuroanatomy of coma can be divided into three major cat- a Secondary to bilateral frontal/basal forebrain dysfunction.
egories: diffuse brain dysfunction or bithalamic injury, primary b
brain stem disorders, and secondary brain stem compression from Secondary to basis pontis dysfunction.
supratentorial and infratentorial mass lesions.
• Most cases of coma are due to metabolic disorders or exogenous features; for example, the sleeping person is not aware of himself or
drug intoxication. herself and in this respect is unconscious. Of course, the important
• Patient evaluation must follow an orderly sequence, beginning with difference is that a sleeping person can be aroused to full consciousness.
vital signs, general physical examination, and neurologic examination. Furthermore, electrodiagnostic evaluation differs in the two conditions
• The neurologic examination of the patient in coma is brief and (see below) and cerebral glucose uptake does not decrease during sleep
focuses on (1) level of consciousness, (2) pupils, (3) eye move- but does so in coma. Drowsiness (“lethargy”) is a state of reduced spon-
ments, (4) motor responses, and (5) respiratory pattern. taneous physical and mental activity. A drowsy person cannot sustain
wakefulness without external stimulation. It is similar in appearance to
• Computed tomographic (CT) scanning of the brain is the most light sleep and almost always accompanied by reduced attention, con-
valuable acute test to rule out structural causes of coma. centration, and mild confusion.
• Hypoxic-ischemic encephalopathy after cardiopulmonary arrest may A stuporous patient appears asleep and requires repeated, stronger
be ameliorated by targeted hypothermia and supportive measures. stimuli to arouse, yet may not achieve full state of arousal and quickly
• Serial neurologic examination over the first 72 hours is most help- drifts back to persistent inactivity when the stimulus is withdrawn.
ful to determine the prognosis for patients with atraumatic coma; When aroused, this patient may or may not open their eyes and par-
for anoxic brain injury, failure to recover pupillary responses or tially respond to requests. At times, restlessness and motor stereotypes
corneal reflexes in the first 72 hours is a poor prognostic sign. are observed. Sopor, the Latin word for deep sleep and a term used in
• As therapies aimed at cerebral resuscitation and preservation following some European countries, denotes an intermediate state between stupor
and coma.
acute injury are developed and proved efficacious, prior guidelines for Delirium is characterized as a reduction in clarity of mentation
determining prognosis will require redefinition and reconfirmation. accompanied by cognitive changes such as memory deficit, altered
• The Uniform Determination of Death Act states that, “An individual speech, or orientation. Its duration of onset is hours or days and there
who has sustained either (1) irreversible cessation of circulatory and is fluctuation in severity during its course. Disorientation affects time
respiratory functions, or (2) irreversible cessation of all functions of followed by place and lastly people in the environment. There may be an
the entire brain, including the brain stem, is dead.” associated anxiety state or agitation. Delirium typically implies diffuse
• The determination of death by brain criteria is based on clinical impairment of bilateral cortical structures usually by a toxic-metabolic
examination, and in most cases does not require confirmatory process and it is typically reversible.
tests. However, the cause of coma must be known, and the cause Dementia is a chronic condition in which content of consciousness
must be sufficient to explain irreversible cessation of whole brain is affected without effect on level of arousal, except in severe terminal
function. The new AAN guidelines recommend a single clinical cases. It is generally progressive and affects memory and at least two
neurological examination. cognitive domains such as language, executive function, planning motor
tasks, and recognition. Dementia is caused by damage to the cerebral
hemispheres by degenerative diseases, traumatic brain injury, hydro-
cephalus, etc.
NORMAL AND IMPAIRED CONSCIOUSNESS: Coma (from the Greek komas, or deep sleep) is a state of unrespon-
A CONCEPTUAL APPROACH siveness in which the patient is incapable of arousing to external or
internal stimuli (lack of alertness). The degree of coma can vary from
Consciousness is a difficult term to define, and even more complicat- lighter stages (also denoted as semicoma) with observed changes in auto-
ing is the fact that many different meanings and classification systems nomic function or brief moaning to strong stimulation, to the deepest
exist for the various states of decreased level of consciousness, such as stage with absence of any brain stem responses (eg, pupillary and cor-
drowsiness, stupor, and coma. For practical reasons, however, in the neal reflexes), cyclic autonomic activity, and motor tone. For in-depth
evaluation of consciousness most clinicians give greater weight to the discussions of this topic, the reader is referred to the major textbooks in
patient’s responses and behavior than to what the patient says. Hence, neurology and to the seminal work by Posner et al. 1
consciousness can be defined in its simplest form as the patient’s aware- A vegetative state can follow coma and identifies a state in which the
ness of self and environment and the responsiveness to his or her needs and brainstem and diencephalic (thalamic) activity is present to a degree
external stimulation. The level of consciousness used in clinical practice that clinical signs of spontaneous arousal are observed; however,
refers to the state of arousal and should be separated from the content clinical evidence of awareness of self and environment is lacking. The
2
of consciousness, which describes various forms of cognitive behaviors patients often show blink responses to light; intermittent eye movements
and thinking. An awake person is fully responsive (alert) to stimuli and (sometimes erroneously interpreted as following objects or looking
is able to specify their extent of awareness of self and environment. at family members); stimulus-sensitive automatisms such as swallow-
Impaired consciousness is generally categorized by the level of respon- ing, bruxism, and moaning, as well as primitive motor responses and
siveness to external and internal stimuli (Table 88-1). Sleep and cycles of sleeping and waking. If this state lasts longer than 30 days,
pathologic states of consciousness undeniably share some common it is referred to as persistent vegetative state (PVS) and is used as a

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