Altered Mental Status: Definition, Causes & Diagnosis

Instructor: Leasha Roy

Leasha is licensed as a registered nurse and clinical nurse specialist. She has over 17 years of nursing experience in a variety of settings and roles including long-term care, acute care, critical care, education, and leadership.

Altered mental status can be the result of a number of factors. This lesson will define altered mental status and discuss the causes and diagnosis of this condition.

Altered Mental Status

Have you ever seen someone who may have consumed a bit too much alcohol? They appear sleepy, confused, and stumble when walking. Or maybe think of someone who's suffered a head injury and is very drowsy and unable to remain awake.

These people are exhibiting signs of altered mental status. Altered mental status (AMS) is a broad term used to indicate an abnormal state of alertness or awareness. Indicators of AMS can vary, but frequently present as one or more of the following:

  • Drowsiness, inability to stay awake
  • Difficult to wake, excessive sleeping
  • Confusion
  • Disorientation (inability to determine correct name, date, location, and/or situation)
  • Forgetfulness
  • Strange behavior, altered judgement

The severity of these symptoms can range from mild (slight confusion or forgetfulness) to severe (complete disorientation or coma), which can sometimes make identification difficult.

Causes of AMS

AMS generally occurs as the result of an underlying condition or disease rather than being a disease itself. In other words, AMS does not typically occur by itself.

For instance, thinking back to the examples presented earlier, the sources of the altered mental status were alcohol intoxication and head trauma. For this reason, when AMS occurs, it is important to determine the causative factor so that proper treatment can be administered. Some possible causes include:

  • Low oxygen
  • Stroke
  • Alcohol
  • Delirium or dementia
  • Infection
  • Tumor
  • Opiates
  • Seizure
  • Trauma
  • High/Low blood sugar

Our treatment for alcohol intoxication would be very different from how we would treat a head injury. Despite the treatment, the desired result would still be a return to the person's baseline level of functioning.

Common causes of altered mental status
Causes of AMS

Diagnostic Tests

While treatments vary widely depending on cause, the diagnostic tests for determining the source of AMS is pretty consistent. Let's review some of those tests now.

  • Gather history

While gathering history isn't technically a test, it is probably one of the most important tasks to perform when trying to figure out the source of the AMS.

Healthcare providers will ask various questions about the person's medical history (including any medical or psychiatric illness), medications, recent surgeries, and drug or alcohol use. The provider will also want to know the person's baseline status, what he/she was doing prior to the change, and how long since the patient was last seen in a normal state.

They may also ask about what the person has recently consumed or places the person may have recently traveled.

  • Vital signs

Obtaining vital signs is the likely next step in information gathering. Measurement of the temperature, heart rate, blood pressure, and respiratory rate are non-invasive tests that can elicit some very important information about what's going on inside the body.

For instance, a fever may be indicative of an infection; a high heart rate could be the result of several conditions including dehydration, low blood volume, or sepsis (severe infection). A pulse oximetry, or oxygen level, is often measured with the vital signs and can reveal data on how well the lungs are functioning.

Abnormal vital signs can also indicate the need for further tests.

  • Physical exam

A focused neurological exam should be performed to determine the extent of the AMS. This will typically include assessing the person's alertness, orientation, memory, reflexes, and ability to follow commands.

  • Blood tests

Drawing blood for labs is simple and usually only involves a quick needle puncture. Tests completed when investigating AMS may include blood counts, electrolytes, glucose, blood cultures, thyroid function, and drug screen (this test may also be performed on urine).

An arterial blood test may also be drawn to determine if any acid/base imbalances are present. These labs all help to determine how well the liver, lungs, and kidneys are performing, as well as finding potential infection.

  • Lumbar puncture

A lumbar puncture involves a physician inserting a needle into the spinal column to collect a specimen of cerebral spinal fluid for lab tests. This test is often done when meningitis is suspected.

Lumbar punctures can be performed if meningitis is the suspected cause of AMS
Lumbar puncture

  • Radiologic tests

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