Understanding the Different Levels of Consciousness

woman shaking an unconscious man
Shake an unconscious patient to wake them. Bicek Photography

A severe lack of consciousness is referred to as being unconscious. Victims are usually considered unconscious if they can't wake up enough to interact normally with the rescuer.

Levels of Consciousness

Consciousness is not a lights-on/lights-off proposition, which the term unconscious implies. It's like being underwater. The deeper you go, the darker the surroundings. As you get closer to the surface you start to see more things and be more cognizant of what's out there, until you break through to total awareness.

Healthcare workers call this sliding scale of awareness the levels of consciousness. Being fully awake, alert and oriented to your surroundings is the gold standard. It's the way most of us go through our days (other than Mondays anyway).

Anything other than that gold standard is considered altered, hence the term altered levels of consciousness. The deepest, darkest level is usually described as being unresponsive, meaning nothing you do to the patient--smells, touch, noises, pain--will arouse them to any sort of response.

Coma is a simplistic term for an unconscious patient who is unresponsive to verbal or physical attempts to wake him or her. Usually, the term coma is used for patients who exhibit unresponsiveness for long periods of time, but it doesn't matter.

It's in the Noggin

Consciousness is a function of the brain and altered levels of consciousness are indicators that something is amiss.

In that way, an altered level of consciousness is a sign of a medical condition, rather than a medical condition in itself. The more acute or sudden changes in consciousness occur, the more we are usually concerned about what it means.

For example: sudden cardiac arrest leads to a sudden loss of consciousness because blood stops flowing to the brain.

In cardiac arrest, the brain isn't the problem--the heart is. However, the sudden loss of consciousness is an obvious indicator of a problem. Any sudden loss of consciousness is a medical emergency and rescuers should call 911 immediately.

Causes of Unconsciousness

There are several medical conditions that change consciousness. Emergency healthcare providers use mnemonics to remember the most common causes. It's a way to run through all the possible problems and rule out the stuff that's not causing the change. Once you've eliminated the issues that aren't a problem, you'll be left with the probable culprit.

One of the easiest ways to remember the usual suspects is to use the mnemonic AEIOU TIPS:

  • A - alcohol
    This one is pretty self explanatory. Many of us have experienced ethanol-induced altered levels of consciousness.
  • E - epilepsy or exposure (heat stroke, hypothermia)
    One reason I'm not a huge proponent of these types of mnemonics is when folks hijack the letters to use them for more than one cause. Oh well, AEIOU TIPS is easy to remember so I deal with the extra stuff. Epilepsy is a seizure condition, a true brain issue. Exposure--hot or cold--affects the brain's ability to function.
  • I - insulin (diabetic emergency)
    Diabetic emergencies affect the brain because the brain only has one fuel that it can burn for energy--sugar. Too little sugar in the bloodstream and the brain runs out of steam. Insulin regulates blood sugar, hence the connection.
  • O - overdose or oxygen deficiency
    Again with the double play. Overdose brings us back to alcohol (some folks remember 'A' to mean alcohol or drugs rather than co-opting 'O' twice). Both of these are pretty easy to understand.
  • U - uremia (toxins due to kidney failure)
    If you don't keep your blood clean, your brain won't work correctly.
  • T - trauma (shock or head injury)
    Either direct injury to the noggin or the loss of too much blood can affect the brain.
  • I - infection
    A systemic infection that affects the entire body--sepsis--or something affecting just the brain and spinal cord, such as meningitis or encephalitis, will cause the brain to malfunction.
  • P - poisoning
    See Alcohol or Overdose, above.
  • S - stroke
    This is the only thing on the list that is truly brain-specific. A stroke is a medical condition that works like an injury to the brain, but doesn't require direct force.

Altered levels of consciousness can be very challenging to figure out.

If you have a patient that just won't wake up and you're not sure why, call 911.

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