An Overview of Level of Consciousness (LOC)

"Level of consciousness" (LOC) is a medical term used to describe how awake, alert, and aware you are. It also refers to how well you respond to attempts to get your attention. A person with an altered level of consciousness may have decreased cognitive function or be difficult to arouse.

A variety of medical conditions and drugs can affect your level of consciousness, from having dementia or lethargy to being in a coma. Sometimes impaired consciousness is reversible, while other times it is not.

This article covers normal and altered states of consciousness as well as coma classifications.

What Is Consciousness?

Medical definitions say a normal LOC means a person is either awake or can be readily awakened from normal sleep. Terms include:

• Consciousness: A state in which a person is awake, aware, alert, and responsive to stimuli
• Decreased consciousness: A person appears awake and aware of their surroundings (conscious) but is not responding normally (acts confused, odd, or sleepy).
  
• Unconsciousness: A person has a deficit in awareness and responsiveness to stimuli (touch, light, sound)

Sleeping is not considered unconsciousness if waking up would result in normal consciousness Between consciousness and unconsciousness there are several altered levels, each with its own definition.

Altered Level of Consciousness

Altered or abnormal levels of consciousness are states in which you either have decreased cognitive function or cannot be easily aroused.

Most medical conditions affect the brain and impair consciousness when they become serious or life-threatening. An altered LOC usually signals a serious medical problem.

Often, an altered LOC can deteriorate rapidly from one stage to the next. They require timely diagnosis and prompt treatment.

Confusion

Confusion describes disorientation that makes it difficult to:

• Reason
• Provide a medical history
• Participate in a medical examination

Causes include:

• Sleep deprivation
• Fever
• Medications
• Alcohol intoxication
• Recreational drug use
• Postictal state (recovering from a seizure)

Delirium

Delirium is a term for an acute confused state. It involves impaired cognition (thought processes) and may include:

• Attention deficits
• Sleep-wake cycle changes
• Hyperactivity (agitation) or hypoactivity (apathy)
• Hallucinations (seeing things that are not there) or delusions (false beliefs)
• Heart rate and blood pressure instability

Causes can include:

• Alcohol withdrawal
• Recreational drugs
• Medications
• Severe infection or illness
• Organ failure

Lethargy and Somnolence

Lethargy and somnolence (sleepiness) involve:

• Severe drowsiness
• Listlessness
• Apathy
• Reduced alertness

A lethargic person may need a gentle touch or verbal stimulation before they will respond.

Causes can include:

• Severe illness or infection
• Recreational drugs
• Organ failure

Obtundation

Obtundation is reduced alertness with:

• Slow responses to stimuli
• Need of repeated stimulation to maintain attention
• Prolonged periods of sleep
• Drowsiness between these periods

Causes can include:

• Poisoning
• Stroke
• Brain edema (swelling)
• Sepsis (a blood infection)
• Advanced organ failure

Stupor

Someone in a stupor responds minimally to vigorous stimulation, such as a pinched toe or light in the eyes.

Causes can include:

• Stroke
• Drug overdose
• Lack of oxygen
• Brain edema
• Myocardial infarction (heart attack)

Coma

A person in a coma does not respond to any stimuli. Their pupils may not react to light, and they may not have a gag reflex.

Comas are caused by severely diminished brain function. This is usually due to:

• Stroke
• Alcohol poisoning
• Extreme hyperglycemia or hypoglycemia
• Extreme blood loss
• Organ failure
• Brain damage or infection

The causes of altered LOC may overlap. For example, the early stages of brain edema or organ failure can cause confusion but then advance rapidly through lethargy, obtundation, stupor, and coma.

Levels of Consciousness Assessment Scale

Levels of consciousness can be subdivided into levels that further clarify your degree of unresponsiveness. That helps improve communication among healthcare providers as well as aiding in research.

Several systems have been developed to standardize these classifications. The most common classification systems are:

• Grady Coma Scale: Grades a coma from I to V. Grady is based on the state of awareness and response to stimuli (e.g., name being called, light pain, deep pain). Grade I indicates confusion, while V indicates coma (no response to stimuli).
• Glasgow Coma Scale: Scores the level of consciousness from 1 to 15, with 15 being normal LOC. This scale takes into account verbal, motor, and eye responses to stimuli.

Summary

Levels of consciousness range from normal alertness and attention to gradations of altered states, including confusion, delirium, stupor, and coma.

The same conditions may produce mild to severe states of altered LOC. Sometimes, there may be a rapid progression from a mild to a high stage.

Coma scales can help describe the exact level of consciousness.