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Delirium commonly manifests as inattention and confusion. It is usually seen in older patients with severe illness. Clouding of consciousness has classically been used to describe a patient’s symptoms.


  1. Almost any illness can lead to delirium in a susceptible patient.

  2. Delirium often complicates medical or surgical hospitalizations.

  3. The most important clues to delirium are the acuity of onset and the fluctuation of course.

  4. Delirium most commonly occurs in older persons and in patients with underlying neurologic disease.

    image There is always a cause of delirium. Clinicians must recognize delirium and identify the cause.

  5. Several conditions are more likely to cause delirium than others.

    1. Severe illness

    2. Drug toxicity

    3. Fluid and electrolyte disturbances (hyponatremia and azotemia)

    4. Infections

    5. Hypothermia or hyperthermia

  6. Delirium is very common in sick, hospitalized patients over the age of 65.

    1. 10% of emergency department patients

    2. 12–25% of medical patients

    3. 20–50% of surgical patients (highest in patients after hip replacement)

  7. image Most acutely ill, older patients who have an acute deterioration in mental status are suffering from delirium.

  8. The prognosis of delirium is poor.

    1. Although reliable data is difficult to obtain, delirium is a predictor of poor outcomes.

    2. Meta-analysis shows that, after controlling for age, sex, comorbid illness or illness severity, and baseline dementia, patients who experienced delirium had a higher risk of death, institutionalization, and dementia during follow-up.

      1. The mortality rate, over about 2 years, for patients in whom delirium developed was 38%.

      2. The rate of institutionalization, over about a year, was 33.4%.

      3. The rate of developing dementia over the next 4 years was 62.5%.

    3. In this same study, patients with dementia and delirium had the highest risk of death.

  9. Delirium is often persistent. Many studies show that most patients in whom delirium develops have at least some persistent symptoms at discharge. These symptoms may be present for months.

    image Only a small percentage of patients with delirium have complete resolution of symptoms with treatment of the underlying disease and return home.

  10. Delirium can occasionally “unmask” underlying dementia. This occurs when a patient with a mild, undiagnosed dementia becomes delirious in the hospital and is then evaluated more fully for cognitive impairment.


  1. Pretest probability

    1. Predictors of delirium have been identified. These help provide pretest probabilities.

    2. One study developed a model to determine a patient’s risk of delirium developing while in the hospital. Predictors included:

      1. Vision impairment

      2. Severe illness

      3. Cognitive impairment

      4. High blood urea nitrogen/creatinine ratio

    3. In a patient population with a mean age of 78, the number of risk factors present correlated with the risk of developing delirium.

      1. No risk factors: 3% chance of delirium developing.

      2. 1 or 2 risk factors: 14% chance of delirium developing.

      3. 3 or 4 risk factors: 26% chance of delirium developing.

    4. Several predictors from another study, with ORs for association with delirium, are listed below:

      1. Abnormal sodium level (OR 6.2)

      2. Severe illness (OR 5.9)

      3. Chronic cognitive impairment ...

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