An altered level of consciousness is any measure of
arousal
Arousal is the physiology, physiological and psychology, psychological state of being awoken or of Five senses, sense organs stimulated to a point of perception. It involves activation of the ascending reticular activating system (ARAS) in the hu ...
other than normal. Level of consciousness (LOC) is a measurement of a person's arousability and responsiveness to
stimuli from the environment.
[
] A mildly depressed level of
consciousness
Consciousness, at its simplest, is awareness of a state or object, either internal to oneself or in one's external environment. However, its nature has led to millennia of analyses, explanations, and debate among philosophers, scientists, an ...
or
alertness
Alertness is a state of active attention characterized by high sensory awareness. Someone who is alert is vigilant and promptly meets danger or emergency, or is quick to perceive and act. Alertness is a psychological and physiological state.
Lac ...
may be classed as
lethargy
Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness, or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overw ...
; someone in this state can be aroused with little difficulty.
People who are
obtunded have a more depressed level of consciousness and cannot be fully aroused.
Those who are not able to be aroused from a sleep-like state are said to be
stupor
Stupor is the lack of critical mental function and a level of consciousness, in which an affected person is almost entirely unresponsive and responds only to intense stimuli such as pain. The word derives from the Latin '' stupor'' ("numbness, in ...
ous.
Coma
A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to Nociception, respond normally to Pain, painful stimuli, light, or sound, lacks a normal Circadian rhythm, sleep-wake cycle and does not initiate ...
is the inability to make any purposeful response.
Scales such as the
Glasgow coma scale have been designed to measure the level of consciousness.
An altered level of consciousness can result from a variety of factors, including alterations in the chemical environment of the brain (e.g. exposure to
poison
A poison is any chemical substance that is harmful or lethal to living organisms. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figurati ...
s or
intoxicant
A psychoactive drug, psychopharmaceutical, mind-altering drug, consciousness-altering drug, psychoactive substance, or psychotropic substance is a chemical substance that alters psychological functioning by modulating central nervous system acti ...
s), insufficient
oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
or
blood flow
Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamics, dynamics of blood flow. The circulatory system is controlled by homeostasis, homeostatic mechanisms of autoregulation, just as hydrau ...
in the brain, and excessive
pressure within the skull. Prolonged unconsciousness is understood to be a sign of a
medical emergency
A medical emergency is an acute injury or illness that poses an immediate risk to a person's life or long-term health, sometimes referred to as a situation risking "life or limb". These emergencies may require assistance from another, qualified ...
.
A deficit in the level of consciousness suggests that both of the
cerebral hemisphere
The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres ...
s or the
reticular activating system
The reticular formation is a set of interconnected nuclei in the brainstem that spans from the lower end of the medulla oblongata to the upper end of the midbrain. The neurons of the reticular formation make up a complex set of neural networks ...
have been injured.
[Porth, p. 838] A decreased level of consciousness correlates to increased
morbidity
A disease is a particular abnormal condition that adversely affects the structure or function of all or part of an organism and is not immediately due to any external injury. Diseases are often known to be medical conditions that are asso ...
(sickness) and
mortality (death).
[Scheld ''et al.''. p. 530] Thus it is a valuable measure of a patient's medical and neurological status. In fact, some sources consider level of consciousness to be one of the
vital signs.
[
]
Definition
Scales and terms to classify the levels of consciousness differ, but in general, reduction in response to stimuli indicates an altered level of consciousness:
Altered level of consciousness is sometimes described as altered
sensorium
A sensorium (/sɛnˈsɔːrɪəm/) (: sensoria) is the apparatus of an organism's perception considered as a whole. It is the "seat of sensation" where it experiences, perceives and interprets the environments within which it lives. The term ori ...
.
Glasgow Coma Scale
The most commonly used tool for measuring LOC objectively is the
Glasgow Coma Scale (GCS). It has come into almost universal use for assessing people with
brain injury
Brain injury (BI) is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors. In general, brain damage refers to significant, undiscriminating trauma-induced damage.
A common ...
,
or an altered level of consciousness. Verbal, motor, and eye-opening responses to stimuli are measured, scored, and added into a final score on a scale of 3–15, with a lower score being a more decreased level of consciousness.
Others
The
AVPU scale is another means of measuring LOC: people are assessed to determine whether they are alert, responsive to verbal stimuli, responsive to painful stimuli, or unresponsive.
To determine responsiveness to voice, a caregiver speaks to, or, failing that, yells at the person.
Responsiveness to pain is determined with a mild painful stimulus such as a pinch; moaning or withdrawal from the stimulus is considered a response to pain.
The ACDU scale, like AVPU, is easier to use than the GCS and produces similarly accurate results.
Using ACDU, a patient is assessed for alertness, confusion, drowsiness, and unresponsiveness.
The
Grady Coma Scale classes people on a scale of I to V along a scale of confusion, stupor, deep stupor,
abnormal posturing
Abnormal posturing is an involuntary flexion or extension of the arms and legs, indicating severe brain injury. It occurs when one set of muscles becomes incapacitated while the opposing set is not, and an external stimulus such as pain caus ...
, and coma.
Pathophysiology
Although the neural science behind alertness, wakefulness, and arousal are not fully known, the
reticular formation
The reticular formation is a set of interconnected nuclei in the brainstem that spans from the lower end of the medulla oblongata to the upper end of the midbrain. The neurons of the reticular formation make up a complex set of neural networks ...
is known to play a role in these.
The
ascending reticular activating system is a postulated group of neural connections that receives sensory input and projects to the
cerebral cortex
The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. It is the largest site of Neuron, neural integration in the central nervous system, and plays ...
through the
midbrain
The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum.
It is functionally associated with vision, hearing, mo ...
and
thalamus
The thalamus (: thalami; from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter on the lateral wall of the third ventricle forming the wikt:dorsal, dorsal part of the diencephalon (a division of ...
from the reticular formation.
Since this system is thought to modulate wakefulness and sleep, interference with it, such as injury, illness, or metabolic disturbances, could alter the level of consciousness.
Normally, stupor and coma are produced by interference with the
brain stem
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is co ...
, such as can be caused by a
lesion
A lesion is any damage or abnormal change in the tissue of an organism, usually caused by injury or diseases. The term ''Lesion'' is derived from the Latin meaning "injury". Lesions may occur in both plants and animals.
Types
There is no de ...
or indirect effects, such as
brain herniation
Brain herniation is a potentially deadly side effect of very high pressure within the skull that occurs when a part of the human brain, brain is squeezed across structures within the human skull, skull. The brain can shift across such structures ...
.
Mass lesions in the brain stem normally cause coma due to their effects on the reticular formation.
[
] Mass
lesion
A lesion is any damage or abnormal change in the tissue of an organism, usually caused by injury or diseases. The term ''Lesion'' is derived from the Latin meaning "injury". Lesions may occur in both plants and animals.
Types
There is no de ...
s that occur
above the
tentorium cerebelli
The cerebellar tentorium or tentorium cerebelli (Latin for "tent of the cerebellum") is one of four dural folds that separate the cranial cavity into four (incomplete) compartments. The cerebellar tentorium separates the cerebellum from the cere ...
normally do not significantly alter the level of consciousness unless they are very large or affect both
cerebral hemisphere
The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres ...
s.
Diagnosis
Assessing LOC involves determining an individual's response to external stimuli.
[
] Speed and accuracy of responses to questions and reactions to stimuli such as touch and pain are noted.
Reflex
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus.
Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...
es, such as the
cough
A cough is a sudden expulsion of air through the large breathing passages which can help clear them of fluids, irritants, foreign particles and Microorganism, microbes. As a protective reflex, coughing can be repetitive with the cough reflex fol ...
and gag reflexes, are also means of judging LOC.
Once the level of consciousness is determined, clinicians seek clues for the cause of any alteration.
Usually the first tests in the ER are pulse oximetry to determine if there is hypoxia, serum glucose levels to rule out hypoglycemia. A urine drug screen may be sent. A CT head is very important to obtain to rule out bleed. In cases where meningitis is suspected, a lumbar puncture must be performed. A serum TSH is an important test to order. In select groups consider vitamin B12 levels. Checking serum ammonia is particularly advised in neonatal coma to discern
inborn errors of metabolism.
Differential diagnosis
A lowered level of consciousness indicate a deficit in brain function.
Level of consciousness can be lowered when the brain receives insufficient oxygen (as occurs in
hypoxia); insufficient blood (as occurs in
shock, in children for example due to
intussusception); or has an alteration in the
brain's chemistry.
Conditions of the heart and
conditions of the lungs can alter consciousness.
Metabolic disorder
A metabolic disorder is a disorder that negatively alters the body's processing and distribution of macronutrients, such as proteins, fats, and carbohydrates. Metabolic disorders can happen when abnormal chemical reactions in the body alter the ...
s such as
diabetes mellitus
Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained hyperglycemia, high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or th ...
and
uremia
Uremia is the condition of having high levels of urea in the blood. Urea is one of the primary components of urine. It can be defined as an excess in the blood of amino acid and protein metabolism end products, such as urea and creatinine, which ...
can alter consciousness.
Hypo- or
hypernatremia
Hypernatremia, also spelled hypernatraemia, is a high concentration of sodium in the blood. Early symptoms may include a strong feeling of thirst, weakness, nausea, and loss of appetite. Severe symptoms include confusion, muscle twitching, and ...
(decreased and elevated levels of
sodium
Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...
, respectively) as well as
dehydration
In physiology, dehydration is a lack of total body water that disrupts metabolic processes. It occurs when free water loss exceeds intake, often resulting from excessive sweating, health conditions, or inadequate consumption of water. Mild deh ...
can also produce an altered LOC.
[
] A
pH outside of the range the brain can tolerate will also alter LOC.
Exposure to
drug
A drug is any chemical substance other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect. Consumption of drugs can be via insufflation (medicine), inhalation, drug i ...
s (e.g.
alcohol
Alcohol may refer to:
Common uses
* Alcohol (chemistry), a class of compounds
* Ethanol, one of several alcohols, commonly known as alcohol in everyday life
** Alcohol (drug), intoxicant found in alcoholic beverages
** Alcoholic beverage, an alco ...
) or
toxin
A toxin is a naturally occurring poison produced by metabolic activities of living cells or organisms. They occur especially as proteins, often conjugated. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived ...
s may also lower LOC,
as may a
core temperature
Normal human body temperature (normothermia, euthermia) is the typical temperature range found in humans. The normal human body temperature range is typically stated as .
Human body temperature varies. It depends on sex, age, time of day, exert ...
that is too high or too low (
hyperthermia
Hyperthermia, also known as overheating, is a condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme te ...
or
hypothermia
Hypothermia is defined as a body core temperature below in humans. Symptoms depend on the temperature. In mild hypothermia, there is shivering and mental confusion. In moderate hypothermia, shivering stops and confusion increases. In severe ...
). Increases in
intracranial pressure
Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adu ...
(the pressure within the skull) can also cause altered LOC. It can result from
traumatic brain injury
A traumatic brain injury (TBI), also known as an intracranial injury, is an injury to the brain caused by an external force. TBI can be classified based on severity ranging from mild traumatic brain injury (mTBI/concussion) to severe traumati ...
such as
concussion
A concussion, also known as a mild traumatic brain injury (mTBI), is a head injury that temporarily affects brain functioning. Symptoms may include headache, dizziness, difficulty with thinking and concentration, sleep disturbances, a brief ...
.
Ischemic stroke
Stroke is a medical condition in which poor blood flow to a part of the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop ...
and
brain bleeding are other causes of altered consciousness.
Infection
An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...
s of the
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...
may also be associated with decreased LOC; for example, an altered LOC is the most common symptom of
encephalitis
Encephalitis is inflammation of the Human brain, brain. The severity can be variable with symptoms including reduction or alteration in consciousness, aphasia, headache, fever, confusion, a stiff neck, and vomiting. Complications may include se ...
.
[
] Neoplasm
A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
s within the
intracranial cavity can also affect consciousness,
as can
epilepsy
Epilepsy is a group of Non-communicable disease, non-communicable Neurological disorder, neurological disorders characterized by a tendency for recurrent, unprovoked Seizure, seizures. A seizure is a sudden burst of abnormal electrical activit ...
and
post-seizure states.
A decreased LOC can also result from a combination of factors.
A
concussion
A concussion, also known as a mild traumatic brain injury (mTBI), is a head injury that temporarily affects brain functioning. Symptoms may include headache, dizziness, difficulty with thinking and concentration, sleep disturbances, a brief ...
, which is a mild traumatic brain injury (MTBI) may result in decreased LOC.
Treatment
Treatment depends on the degree of decrease in consciousness and its underlying cause. Initial treatment often involves the administration of
dextrose
Glucose is a sugar with the molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae during photosynthesis from water an ...
if the blood sugar is low as well as the administration of
oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
,
naloxone
Naloxone, sold under the brand name Narcan among others, is an opioid antagonist, a medication used to reverse or reduce the effects of opioids. For example, it is used to restore breathing after an opioid overdose. Effects begin within two ...
and
thiamine
Thiamine, also known as thiamin and vitamin B1, is a vitamin – an Nutrient#Micronutrients, essential micronutrient for humans and animals. It is found in food and commercially synthesized to be a dietary supplement or medication. Phosp ...
.
See also
*
Altered state of consciousness
An altered state of consciousness (ASC), also called an altered state of mind, altered mental status (AMS) or mind alteration, is any condition which is significantly different from a normal waking state. It describes induced changes in one's me ...
*
Disorders of consciousness
Disorders of consciousness are medical conditions that inhibit consciousness. Some define disorders of consciousness as any change from complete self-awareness to inhibited or absent self-awareness and arousal. This category generally includes m ...
*
Level of consciousness (esotericism)
*
Cognitive deficit
References
External links
{{DEFAULTSORT:Altered Level Of Consciousness
Neuroscience
Intensive care medicine
Emergency medicine
Central nervous system disorders
Symptoms and signs of mental disorders
Consciousness