| Altered level of consciousness | |
|---|---|
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| Anintracranial hemorrhage, one cause of altered level of consciousness | |
| Specialty | Psychiatry,Neurology |
Analtered level of consciousness is any measure ofarousal other than normal.Level of consciousness (LOC) is a measurement of a person's arousability and responsiveness tostimuli from the environment.[1] A mildly depressed level ofconsciousness oralertness may be classed aslethargy; someone in this state can be aroused with little difficulty.[1] People who areobtunded have a more depressed level of consciousness and cannot be fully aroused.[1][2] Those who are not able to be aroused from a sleep-like state are said to bestuporous.[1][2]Coma is the inability to make any purposeful response.[1][2] Scales such as theGlasgow 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 topoisons orintoxicants), insufficientoxygen orblood flow in the brain, and excessivepressure within the skull. Prolonged unconsciousness is understood to be a sign of amedical emergency.[3] A deficit in the level of consciousness suggests that both of thecerebral hemispheres or thereticular activating system have been injured.[4] A decreased level of consciousness correlates to increasedmorbidity (sickness) andmortality (death).[5] 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 thevital signs.[3][6]
Scales and terms to classify the levels of consciousness differ, but in general, reduction in response to stimuli indicates an altered level of consciousness:
| Level | Summary (Kruse)[2] | Description |
|---|---|---|
| Metaconscious | Preternatural | People who possess the ability to monitor and control their own cognitive processes in addition to meeting all the criteria indicative of a normal level of consciousness. In the field ofcognitive neuroscience, metacognitive monitoring and control have been viewed as functions of theprefrontal cortex, which receives sensory input signals from divergent cortical regions and implements control through feedback loops which are established utilizing the underlying mechanisms ofneuroplasticity (see chapters by Schwartz & Bacon and Shimamura, in Dunlosky & Bjork, 2008).[7] |
| Conscious | Normal | Assessment of LOC involves checkingorientation: people who are able promptly and spontaneously to state their name, location, and the date or time are said to be oriented to self, place, and time, or "oriented X3".[8] A normalsleep stage from which a person is easily awakened is also considered a normal level of consciousness.[9] "Clouding of consciousness" is a term for a mild alteration of consciousness with alterations in attention and wakefulness.[9] |
| Confused | Disoriented; impaired thinking and responses | People who do not respond quickly with information about their name, location, and the time are considered "obtuse" or "confused".[8] A confused person may be bewildered, disoriented, and have difficulty following instructions.[9] The person may have slow thinking and possible memory time loss. This could be caused by sleep deprivation, malnutrition, allergies, environmental pollution, drugs (prescription and nonprescription), and infection. |
| Delirious | Disoriented; restlessness, hallucinations, sometimes delusions | Some scales have "delirious" below this level, in which a person may be restless or agitated and exhibit a marked deficit inattention.[2] |
| Somnolent | Sleepy | Asomnolent person shows excessivedrowsiness and responds to stimuli only with incoherent mumbles or disorganized movements.[8] |
| Obtunded | Decreased alertness; slowed psychomotor responses | Inobtundation, a person has a decreased interest in their surroundings, slowed responses, and sleepiness.[9] |
| Stuporous | Sleep-like state (not unconscious); little/no spontaneous activity | People with an even lower level of consciousness, stupor, only respond bygrimacing or drawing away from painful stimuli.[8] |
| Comatose | Cannot be aroused; no response to stimuli | Comatose people do not even make this response to stimuli, have nocorneal orgag reflex, and they may have nopupillary response to light.[8] |
Altered level of consciousness is sometimes described as alteredsensorium.
The most commonly used tool for measuring LOC objectively is theGlasgow Coma Scale (GCS). It has come into almost universal use for assessing people withbrain injury,[2] 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.[citation needed]
TheAVPU scale is another means of measuring LOC: people are assessed to determine whether they arealert, responsive toverbal stimuli, responsive topainful stimuli, orunresponsive.[3][6] To determine responsiveness to voice, a caregiver speaks to, or, failing that, yells at the person.[3] 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.[3] The ACDU scale, like AVPU, is easier to use than the GCS and produces similarly accurate results.[10] Using ACDU, a patient is assessed foralertness,confusion,drowsiness, andunresponsiveness.[10]
TheGrady Coma Scale classes people on a scale of I to V along a scale of confusion, stupor, deep stupor,abnormal posturing, and coma.[9]
Although the neural science behind alertness, wakefulness, and arousal are not fully known, thereticular formation is known to play a role in these.[9] Theascending reticular activating system is a postulated group of neural connections that receives sensory input and projects to thecerebral cortex through themidbrain andthalamus from the reticular formation.[9] 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.[9]
Normally, stupor and coma are produced by interference with thebrain stem, such as can be caused by alesion or indirect effects, such asbrain herniation.[9] Mass lesions in the brain stem normally cause coma due to their effects on the reticular formation.[11] Masslesions that occurabove thetentorium cerebelli normally do not significantly alter the level of consciousness unless they are very large or affect bothcerebral hemispheres.[9]
Assessing LOC involves determining an individual's response to external stimuli.[12] Speed and accuracy of responses to questions and reactions to stimuli such as touch and pain are noted.[12]Reflexes, such as thecough and gag reflexes, are also means of judging LOC.[12] Once the level of consciousness is determined, clinicians seek clues for the cause of any alteration.[9] 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 discerninborn errors of metabolism.[citation needed]
A lowered level of consciousness indicate a deficit in brain function.[4] Level of consciousness can be lowered when the brain receives insufficient oxygen (as occurs inhypoxia); insufficient blood (as occurs inshock, in children for example due tointussusception); or has an alteration in thebrain's chemistry.[3]Conditions of the heart andconditions of the lungs can alter consciousness.Metabolic disorders such asdiabetes mellitus anduremia can alter consciousness.[12]Hypo- orhypernatremia (decreased and elevated levels ofsodium, respectively) as well asdehydration can also produce an altered LOC.[13] ApH outside of the range the brain can tolerate will also alter LOC.[9] Exposure todrugs (e.g.alcohol) ortoxins may also lower LOC,[3] as may acore temperature that is too high or too low (hyperthermia orhypothermia). Increases inintracranial pressure (the pressure within the skull) can also cause altered LOC. It can result fromtraumatic brain injury such asconcussion.[12]Ischemic stroke andbrain bleeding are other causes of altered consciousness.[12]Infections of thecentral nervous system may also be associated with decreased LOC; for example, an altered LOC is the most common symptom ofencephalitis.[14]Neoplasms within theintracranial cavity can also affect consciousness,[12] as canepilepsy andpost-seizure states.[9] A decreased LOC can also result from a combination of factors.[12]Aconcussion, which is a mild traumatic brain injury (MTBI) may result in decreased LOC.[citation needed]
Treatment depends on the degree of decrease in consciousness and its underlying cause. Initial treatment often involves the administration ofdextrose if the blood sugar is low as well as the administration ofoxygen,naloxone andthiamine.[citation needed]
level of consciousness.
level of consciousness.
Mass lesions within monkey coma by virtue of direct effects on the reticular formation of monkey