Rotation Prep

Published April 8, 2020


Delirium is an acute fluctuating change in mental state, usually due to reversible causes. In contrast with dementia, delirium is characterized by sudden changes typically associated with an acute illness or drug toxicity and is usually reversible. Delirium is common in the elderly: 30% of older adults hospitalized on a medical unit become delirious, and 10% to 50% of older adults undergoing surgery experience delirium.

Delirium is often not recognized, diagnosed, or treated by clinicians. While often thought of as a hyperactive state, the less recognized hypoactive state is more common. Delirium is associated with increased mortality and morbidity. Among hospitalized patients, it is associated with up to a tenfold increase in mortality. Patients who develop delirium as inpatients are more likely to have poor functional outcomes and are at higher risk for death after discharge, as compared with inpatients who do not develop delirium.

Features of Delirium

The altered mental state that characterizes delirium occurs over a short period of time, with alternating levels of consciousness. Hyperactive delirium is characterized by an agitated state and accounts for only 25% of cases. Hypoactive delirium is characterized by withdrawn and depressed states and accounts for the majority of cases.


The Confusion Assessment Method (CAM) is a common tool used to identify the key features of delirium.

The Confusion Assessment Method for Diagnosing Delirium
The presence of delirium requires features 1 and 2 and either 3 or 4:

  • Feature 1: Acute change in mental status with a fluctuating course

  • Feature 2: Inattention

  • Feature 3: Disorganized thinking

  • Feature 4: Altered level of consciousness

Risk Factors

The risk for delirium can be assessed according to the presence of predisposing (baseline) and precipitating (acute) factors as follows:

  • predisposing factors: older age, dementia, multiple comorbidities

  • precipitating factors: surgery, pain, acute illness, constipation, urinary retention, infections, medication use (including anticholinergic drugs, benzodiazepines, and opioids)

The more risk factors for delirium that are present, the more likely a patient is to develop it. A detailed evaluation is key to identifying these risk factors.


The evaluation of delirium should start with a through history and physical examination.

Delirium evaluation tools include the Confusion Assessment Method for the intensive care unit (CAM-ICU), the brief CAM (bCAM) for the emergency department, and the 3-minute diagnostic interview for delirium using CAM (3D-CAM). Evaluation for delirium should include ruling out dementia, depression, and other psychiatric illnesses.

The following table outlines evaluation and management of delirium:

(Source: Delirium in Hospitalized Older Adults. N Engl J Med 2017.)


The key to managing delirium is promptly recognizing and evaluating it and offering nonpharmacologic interventions. Initial evaluation should begin with an assessment of precipitating factors. All reversible or correctable contributing factors should be addressed. For instance, precipitating medications should be substituted with alternatives, as appropriate.

Patient orientation is key in both the hospital and community settings. Food and fluid intake should be monitored to reduce the risks for malnutrition and dehydration.

Nonpharmacologic interventions are important for patients with delirium who experience agitation. Use of restraints should be minimized, as they have been associated with increased risk for injury.

Currently, no medications are approved for management of delirium. Antipsychotic agents are frequently used (off-label) to treat delirium, but numerous studies and meta-analyses indicate that antipsychotics do not reduce the duration or severity of delirium.

For additional information on delirium within NEJM Resident 360, see Altered Mental Status in the Neurology rotation guide.

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