Altered Level of Consciousness
An altered
level of consciousness (LOC) is apparent in the pa-tient who is not
oriented, does not follow commands, or needs persistent stimuli to achieve a
state of alertness. LOC is gauged on a continuum with a normal state of
alertness and full cognition (consciousness) on one end and coma on the other
end. Coma is a clinical state of
unconsciousness in which the patient is unaware of self or the environment for
prolonged periods (days to months or even years). Akinetic mutism is a state of unresponsiveness to the environment
in which the patient makes no movement or sound but sometimes opens the eyes. Persistent vegetative state is a
condition in which the patient is described as wakeful but devoid of conscious
content, without cognitive or affective mental function. The level of
responsiveness and consciousness is the most important indicator of the
patient’s condition.
Altered
LOC is not a disorder itself; rather, it is a function and symptom of multiple
pathophysiologic phenomena. The cause may be neurologic (head injury, stroke),
toxicologic (drug over-dose, alcohol intoxication), or metabolic (hepatic or
renal failure, diabetic ketoacidosis).
The
underlying causes of neurologic dysfunction are disrup-tion in the cells of the
nervous system, neurotransmitters, or brain anatomy.
A
disruption in the basic functional units (neurons) or neuro-transmitters results
in faulty impulse transmission, impeding communication within the brain or from
the brain to other parts of the body. These disruptions are caused by cellular
edema and other mechanisms such as antibodies disrupting chemical trans-mission
at receptor sites.
Intact
anatomic structures of the brain are needed for proper function. The two
hemispheres of the cerebrum must communi-cate, via an intact corpus callosum,
and the lobes of the brain (frontal, parietal, temporal, and occipital) must
communicate and coordinate their specific functions. Additional anatomic
structures of importance are the cerebellum and the brain stem. The cerebellum
has both excitatory and inhibitory ac-tions and is largely responsible for
coordination of movement. The brain stem contains areas that control the heart,
respiration, and blood pressure. Disruptions in the anatomic structures are
caused by trauma, edema, pressure from tumors as well as other mechanisms such
as an increase or decrease in blood or cerebro-spinal fluid (CSF) circulation.
Alterations in LOC occur along a continuum, and the
clinical manifestations depend on where the patient is along this con-tinuum.
As the patient’s state of alertness and consciousness decreases, there will be
changes in the pupillary response, eye open-ing response, verbal response, and
motor response. Initial changes may be reflected by subtle behavioral changes
such as restlessness or increased anxiety. The pupils, normally round and
quickly re-active to light, become sluggish (response is slower); as the
patient becomes comatose, the pupils become fixed (no response to light). The
patient in a coma does not open the eyes, respond verbally, or move the
extremities in response to a request to do so.
The patient with an altered LOC is at risk for
alterations in every body system. A complete assessment is performed, with
particu-lar attention to the neurologic system. The neurologic examina-tion
should be as complete as the LOC allows. It includes an evaluation of mental
status, cranial nerve function, cerebellar function (balance and coordination),
reflexes, and motor and sen-sory function. LOC, a sensitive indicator of
neurologic function, is assessed based on the criteria in the Glasgow Coma
Scale: eye opening, verbal response, and motor response (Bateman, 2001). The
patient’s responses are rated on a scale from 3 to 15. A score of 3 indicates
severe impairment of neurologic function; a score of 15 indicates that the
patient is fully responsive. If the patient is comatose,
with localized signs such as abnor-mal pupillary and motor responses, it is
assumed that neurologic disease is present until proven otherwise. If the
patient is comatose and pupillary light reflexes are preserved, a toxic or
metabolic dis-order is suspected.
Procedures
used to identify the cause of unconsciousness in-clude scanning, imaging,
tomography (eg, computed tomogra-phy, magnetic resonance imaging, positron
emission tomography), and electroencephalography. Laboratory tests include
analysis of blood glucose, electrolytes, serum ammonia, and blood urea
ni-trogen levels, as well as serum osmolality, calcium level, and par-tial
thromboplastin and prothrombin times. Other studies may be used to evaluate
serum ketones and alcohol, drug levels, and arterial blood gas levels.
Potential complications for the patient with
altered LOC include respiratory failure, pneumonia, pressure ulcers, and
aspiration. Respiratory failure may develop shortly after the patient becomes
unconscious. If the patient cannot maintain effective respirations, supportive
care is initiated to provide adequate ventilation. Pneu-monia is common in
patients receiving mechanical ventilation or in those who cannot maintain and
clear the airway. The patient with altered LOC is subject to all the
complications associated with immobility, such as pressure ulcers, venous
stasis, muscu-loskeletal deterioration, and disturbed gastrointestinal
function-ing. Pressure ulcers may become infected and act as a source of
sepsis. Aspiration of gastric contents or feedings may occur, pre-cipitating
the development of pneumonia or airway occlusion.
The
first priority of treatment for the patient with altered LOC is to obtain and
maintain a patent airway. The patient may be orally or nasally intubated, or a
tracheostomy may be performed. Until the patient’s ability to breathe on his or
her own is deter-mined, a mechanical ventilator is used to maintain adequate
oxy-genation. The circulatory status (blood pressure, heart rate) is monitored
to ensure adequate perfusion to the body and brain. An intravenous catheter is
inserted to provide access for fluids and intravenous medications. Neurologic
care focuses on the specific neurologic pathology, if any. Nutritional support,
using either a feeding tube or a gastrostomy tube, is initiated as soon as
possi-ble. In addition to measures to determine and treat the under-lying
causes of altered LOC, other medical interventions are aimed at pharmacologic
management of complications and strategies to prevent complications.
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