Medical Levels of Consciousness

There are different levels of consciousness in medicine

man in coma in hospital
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Level of consciousness (LOC) is a medical term for identifying the degree of a patient's cognitive function. It describes his or her awareness of surroundings and arousal potential. Levels of consciousness are generally based on a person's responsiveness to stimulation.

Consciousness identifies a state in which a patient is awake, aware, alert and responsive to stimuli.

Unconsciousness identifies a state in which a patient is unaware and unresponsive to stimuli.

Between these two main states, there are several levels of conscious. These range from from being alert to being in a coma. 

Normal Level of Consciousness

A normal level of consciousness implies that a patient is either in a state of awareness, alertness and wakefulness, or in one of the stages of normal sleep and from which they can be readily awakened.

Altered Level of Consciousness (ALOC)

Altered or abnormal levels of consciousness describe states that vary between full consciousness and unconsciousness

Altered levels of consciousness can include:

  • Confusion: A disorientation regarding a person, place or time that makes it difficult to reason or follow commands. Causes include sleep deprivation, fever or drug abuse.
  • Delirium: A fluctuating state between hyperawareness, and a state of disorientation and sluggishness. Causes can include intoxication or medications.
  • Lethargy: A state of severe drowsiness, listlessness, apathy accompanied with reduced alertness. It may also be referred to as somnolence. Causes can include anemia, sickness, underactive thyroid and others.
  • Obtundation: A more severe reduction in alertness than with lethargy, along with slow responses to stimuli, longer periods of sleep and drowsiness between these periods. Causes can include seizures and poisoning, among many others.
  • Stupor: A severe level of impaired consciousness in which a person is unresponsive except to vigorous and regular stimulation that must be repeated. Causes can include stroke, drug overdose, lack of oxygen, brain swelling and others.
  • Coma: A state of unresponsiveness, even to stimuli, and may lack a gag reflex or pupillary response.

There are other terms used to describe various degrees and states regarding a person's level of consciousness, such as syncope, which is a brief period of unconsciousness such as when fainting. The states of coma and stupor may also be subdivided into levels or classifications that further clarify the degree of unresponsiveness of a person in one of these states.

Classifications of Coma

Several systems have been developed in order to standardize classifications of coma and improve communication among health care providers. This also aids in research into coma.

One example is the Grady Coma Scale, which rates coma in grades from I - IV. The grades are determined based on the patient's state of awareness and response to stimuli, such as response to the patient's name being called, light pain and deep pain.

Another example is the Glasgow Coma Scale, which uses a score to identify level of consciousness, from 1 to 15, with 15 being a normal state of consciousness.

Lower scores indicate decreased levels of consciousness. It takes into account verbal, motor and eye responses to stimuli for determining the overall score.

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