Altered mental status (AMS) can present as changes in consciousness, appearance, behavior, mood, affect, motor activity, or cognitive function.^1–3 Recent changes are the focus of this article and are approached differently than chronic changes. Recent changes occur within seconds to days and usually pose a more immediate threat to a patient's well-being than chronic changes.^2–4

AMS is common and is estimated to account for 5% of adult emergency department encounters.⁵ Older people are especially susceptible, as evidenced by their high rates of delirium (Table 1).⁶ Additionally, AMS is associated with poor patient outcomes, especially when recognition is delayed.^7,8

The differential diagnosis for AMS is broad. A history and physical examination are the cornerstones of diagnosis, and their findings guide diagnostic testing. Preventive measures can decrease incidence and are important to use in patients at high risk. The goal of treatment is to correct the precipitating cause of the AMS.^2,3,9–11

Causes of Recent AMS

Causes of recent AMS include primary central nervous system insults, systemic infections, metabolic disturbances, toxin exposure, medications, chronic systemic diseases, and psychiatric conditions (Table 2).^2–4,9,10 Although a single abnormality may cause the alteration in mental status (e.g., opiate overdose), often the cause is multifactorial (e.g., dehydration, constipation, high-risk medication use).^2–4,9,10

Among the most common and important presentations of AMS is delirium, especially in older adults who are hospitalized.^6,9 The hallmarks of delirium are acute, fluctuating changes in attention, awareness, and cognition that are not attributable to a neurocognitive disorder. Evidence of a secondary cause of AMS is often also present.^6,9 Other features include sleep disturbances, hallucinations, delusions, inappropriate behavior, and emotional instability.¹¹ Delirium was reviewed in a previous American Family Physician article.⁶

Evaluation

Changes in consciousness, appearance, behavior, mood, affect, or motor activity are usually apparent by general observation and interaction with the patient.

URGENT INTERVENTION

AMS can be caused by a life-threatening condition. Therefore, the first step in evaluating the patient is addressing abnormalities in the airway, breathing, and circulation (ABCs; Figure 1).^{2,3,10,12–18}

Once the ABCs have been stabilized, clinicians should evaluate for other conditions for which rapid intervention is needed to decrease the risk of morbidity and mortality. Abnormal vital signs may identify an obvious cause such as hypothermia, hypoxemia, or a hypertensive emergency, and such abnormalities should be addressed urgently.^2,3,10