Delirium is characterized by an altered level of consciousness, decreased attention span, acute onset, and fluctuating course. About 15% of elderly patients admitted to the hospital have delirium as a presenting or associated symptom. Delirium will develop in another 15% of elderly patients during hospitalization.
In hospitalized patients, delirium is associated with a 10-fold increased risk of death, a 3- to 5-fold increased risk of nosocomial complications, a prolonged stay, and postacute nursing home placement.1In addition, delirium during hospitalization predicts a poor functional recovery and increased risk of death up to 2 years after discharge.2,3 Persistent delirium predicts an especially poor long-term outcome.4
The causes of delirium are often multifactorial. Predisposing and precipitating factors increase a patient's risk (Table 1).5-8 Predisposing factors are often difficult to change but are useful in identifying high-risk patients. Precipitating factors are often modifiable and offer the opportunity for intervention.
A number of medications may precipitate delirium (Table 2).9 Some experts believe that delirium is precipitated by the use of medications with a high anticholinergic burden. This condition may be exacerbated by endogenous anticholinergic activity that occurs in persons with delirium.
Clinical diagnosis may be difficult because delirium shares features with both dementia and depression (Table 3). A thorough history taking is especially important, with particular focus on previous cognitive difficulties, mood disorders, and a review of medications. Traditional screening devices used for depression and dementia, such as the Geriatric Depression Scale and Mini-Mental State Examination, may not yield accurate results in the setting of comorbid delirium. Tests of attention, such as the Digit Span Test, may be useful in identifying those who have a decreased attention span, a cardinal feature of delirium. Family members can often provide valuable information about a patient's baseline cognitive status.
The criteria from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), are the gold standard for diagnosis of delirium (Table 4).10 Alternative criteria have been developed to help clinicians and nonclinical personnel diagnose and rate the severity of delirium. The Confusion Assessment Method is commonly used in inpatient settings and is based on DSM-III-R criteria (Table 5).11 The NEECHAM Confusion Scale is a nursing rating tool that screens for delirium, identifies patients at high risk, and assesses severity in medical inpatients.
Delirium can take several forms. Hyperactive delirium is the most easily recognized because patients with this form often fall or interfere with care. It is characterized by psychomotor agitation, verbal aggression, disorientation, visual hallucinations, and combativeness. Two thirds of hospitalized patients with delirium are hypoactive and hypovigilant, however. Hypoactive delirium is characterized by somnolence and a decreased attention span. Although patients with this form are often overlooked, their delirium carries an equally poor prognosis.