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CHAPTER 17 ■ COMA
ERIC W. GLISSMEYER, DOUGLAS S. NELSON

INTRODUCTION
Consciousness refers to the state of being awake and aware of oneself and one’s
surroundings. It is a basic cerebral function that is not easily compromised;
impairment of this faculty may therefore signal the presence of a life-threatening
condition. An altered level of consciousness (ALOC) is not in itself a disease but
a state caused by an underlying disease process. Coma refers to a state lacking
wakefulness and awareness from which a patient cannot be roused; this represents
the most extreme form of ALOC. Lesser levels of impairment are described using
other terms whose meanings may overlap. Lethargy refers to depressed
consciousness resembling a deep sleep, from which a patient can be aroused but
into which he or she immediately returns. A patient is said to be stuporous or
obtunded when he or she is not totally asleep but demonstrates greatly depressed
responses to external stimuli. Not all ALOC states produce a diminished mental
state, but may include abnormal activation of consciousness such as in delirium
(see Chapter 13 Agitated Child ). Because neurologic status may vary
dramatically over time, it may be difficult to summarize such symptoms using a
single descriptor. Therefore, recording the comatose patient’s specific response
(e.g., body movement, type of vocalization) to a defined stimulus (e.g., a sternal
rub) is preferable ( Table 17.1 ).

PATHOPHYSIOLOGY
The state of wakefulness is mediated by neurons of the ascending reticular
activating system (ARAS) located in the brainstem and pons. Neural pathways
from these locations project throughout the cortex, which is responsible for
awareness. If the function of these neurons is compromised or if both cerebral
hemispheres are sufficiently affected by disease, an ALOC will result.
Proper function of the ARAS and cerebral hemispheres depends on many
factors, including the presence of substrates needed for energy production,

adequate blood flow to deliver these substrates, absence of abnormal serum
concentrations of metabolic waste products or extraneous toxins, maintenance of
body temperature within normal ranges, and the absence of abnormal neuronal
excitation or irritation from seizure activity or central nervous system (CNS)
infection.