Altered Mental Status

“Altered mental status” is a term that is used to describe a range of levels of a patient’s mentation, from mild inattention to complete unresponsiveness. Sorting out the etiology of altered mental status (AMS) and treating reversible causes can shorten length of hospital stay and reduce the risk of further complications. This section provides an overview of the common causes of AMS.

Being specific about a patient’s mental status when describing the alteration to colleagues, consultants, and in the medical record helps determine how urgently the patient needs to be evaluated and treated. Is the patient somnolent, or are they just answering questions inappropriately? Is the patient protecting their airway?

Common Causes of AMS

Delirium

Delirium is the subacute fluctuating change in mental state usually due to reversible causes. Delirium is common: 30% of older adults hospitalized on a medical unit and 10% to 50% of older adults undergoing surgery experience delirium. Although delirium is most common in older adults, middle-aged patients with severe illness in the hospital and intensive care unit (ICU) can also be affected. For more information on delirium in older adults and in the ICU, see the Geriatrics and Critical Care rotation guides.

Other Causes

Delirium is not the only type of AMS in hospitalized patients. If the AMS is acute in onset, persistent (nonfluctuating), or associated with impairment in consciousness, it may not be delirium.

Begin with a focused history, physical, and review of recent events, then determine appropriate next steps depending on the acuity and severity of AMS. Assess the patient’s general status and vital signs: bradycardia, tachyarrhythmia, hypotension, and acute hypertension can all precipitate altered mental status. These conditions are emergencies and must be treated first.

In patients with otherwise normal vital signs, consider the other causes of AMS summarized in the table below. Most patients do not require the entire workup described.

Note: Some research indicates a high rate of abnormal encephalograms (EEGs) in hospitalized patients undergoing evaluation for AMS, suggesting that EEGs may be underutilized as a diagnostic tool for AMS.