Delirium is a sudden and severe change in brain function that causes a person to appear confused or disoriented, or to have difficulties maintaining focus, thinking clearly, and remembering recent events, typically with a fluctuating course. Delirium can be triggered by a serious medical illness such as an infection, certain medications, and other causes, such as drug withdrawal or intoxication. Older patients, over 65 years, are at highest risk for developing delirium. People with previous brain disease or brain damage are also at risk. Some patients become agitated, while others may be quietly confused.
Delirium is distinct from dementia because it develops suddenly, over hours to days, rather than months to years. And unlike dementia, delirium is usually temporary, resolving when the underlying cause is addressed promptly. Delirium also differs from the psychosis of psychiatric disease, in which orientation, concentration, and attention are usually less impaired. However, these features are not always reliable.
The goal of treatment is to address the cause of delirium when possible and to keep the person safe.
It is not clear why or how delirium develops. There are many potential causes, with the most common including infections, medications, and organ failure (such as severe lung or liver disease). The underlying infection or condition is not necessarily a brain problem.
● A urinary tract infection or dehydration can cause delirium in certain people.
● The time after surgery (called the postoperative period) is a common time for delirium to develop, especially in older people. This may be related to pain or the use of anesthesia or pain medications.
● Sepsis, a life-threatening illness caused by the body’s response to severe infection, is often associated with changes in brain function even among people who are young and previously healthy.
Risk factors — Certain underlying conditions increase the risk of delirium:
● Advanced age
● Underlying brain diseases such as dementia, stroke, or Parkinson disease, particularly when there are current problems with memory
● Use of multiple medications (particularly psychiatric drugs and sedatives), or multiple medical problems
● Sudden withdrawal of a regular medication or cessation of regular alcohol use
● Frailty, malnutrition, immobility
● Advanced cancer
● Undertreated pain (although excessive use of opioid pain medication for pain control can also impair brain function)
● Immobilization, including physical restraints
● Use of bladder catheters
● Limb fractures
● Interventions, including diagnostic tests
● Poor eyesight or hearing
● Sleep deprivation
● Organ failure (eg, chronic lung disease; heart, kidney, or liver failure)
How common is delirium? — Nearly 30 percent of older patients experience delirium at some time during hospitalization; the incidence is higher in intensive care units. Among older patients who have had surgery, the risk of delirium varies from 10 to greater than 50 percent.
Delirium is not a disease, but rather a group of symptoms. The key features include:
● There are abnormal changes in the person’s level of consciousness and thinking. The person may be sleepy, or may appear to be withdrawn and depressed (hypoactive delirium) or agitated (hyperactive delirium), or alternate between these states. The changes may be subtle initially.
● The person often has difficulty maintaining focus. He/she may change the subject frequently in a conversation, have difficulty retaining new information, mention strange ideas, or be disoriented (in place or in time). Some patients have visual hallucinations.
These changes develop over a short period of time (hours to days) and tend to become intermittently worse, especially in the afternoon and evening. This sudden change helps to differentiate delirium from dementia, which worsens slowly over months to years.