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Delirium

What It Is, What It Means

Mar 2, 2009 James Cooper

Although often overlooked, delirium is a well defined condition. Delirium is a malfunction of the brain, but it's not dementia. It is a bad omen for an ill person.

“They were going to have a party at last! Delirious with joy, she carefully selected treats and swept them into her shopping cart.”

The delirium of the woman in the last sentence is a metaphor for a medical condition often thought of as full of excitement, but in fact, is frequently frightening, morose, and the opposite of exciting. Delirium is not a joyous state of mind.

Basically, delirium is a condition in which the person can’t pay attention to her environment. She can’t attend to what she sees or hears or feels. She may be awake, but her mind is unable to concentrate on the here and now. Her mind is in a fog, which is a rather good metaphor for delirium.

Delirium occurs in up to 80% of older people in hospital intensive care units. Often called “ICU psychosis,” sometimes “acute confusional state,” or “acute brain failure,” it also occurs outside the hospital, and suggests a grave illness. Some studies indicate it can be missed as a diagnosis half the time.

Types of Delirium

In about a third of cases, the person is hyperactive: agitated, restless, often with nonsensical speech. In about 25% of cases, the opposite is true: the person is sluggish, difficult to arouse. The rest are mixed, varying in activity level.

Hyperactive delirium can cause a patient to try to climb out of bed, pulling out intravenous tubes and falling to the floor. Hypoactive delirium can lead to gagging on food and liquids, bedsores, and blood clots that can go to the lungs.

Formal Definition of Delirium

It’s a disturbance of consciousness with inattention, and/or inaccurate perceptions, that fluctuates over time. It often includes disorientation, memory impairment, and irrelevant speech. “The essential feature of a delirium is a disturbance in consciousness that is accompanied by a change in cognition that cannot be better accounted for by a preexisting or evolving dementia,” according to the reference code, DSM IV. Notice that the definition does not require the presence of hallucinations or delusions.

It’s Not Dementia

While memory loss can be prominent in delirium, delirium is not dementia. It can occur with dementia, but dementia has a slow onset (is not abrupt) and does not have the more rapid swings in symptom intensity. In early dementia, there is not usually the clouding of the mind of delirium. Also, often the cause of delirium can be determined, and, if resolved, there is the expectation the person will return to his previous function level.

What Causes Delirium?

The brain has opposing circuits that are normally in careful balance, tilting one way or the other to accomplish a goal. In delirium, there is an imbalance in neurotransmitters (the chemical messengers that allow brain cells to communicate). Neurotransmitters involved in delirium are dopamine, GABA, and acetylcholine. Relative excess dopamine leads to excitability of neurons, the other two decrease it. Any imbalance can lead to instability and disruption of orderly brain processes.

Infections and stress can produce cytokines that travel in blood to the brain, also disrupting brain cell interactions, causing imbalance of reality calculations (disorientation). Decreased blood circulation, medications, and changes in endorphin function can lead to or cause delirium.

Immature brains are more susceptible—infants can get delirium with high fever, with no further implications. On the other end of the spectrum, older brains, presumably with less redundancy in control circuits, are also more susceptible, possibly with implications of decreased overall capacity.

The Confusion Assessment Method (CAM)

Nurses and other health professionals often use the CAM to evaluate if delirium is present. CAM suggests five criteria.

Sudden or rapid change in mental status
Signs that fluctuate over minutes or hours
Inattention (example: answering challenges incorrectly)
Level of consciousness not normal (can be hyper- or hypo-)
Disorganized thinking (example: rambling speed)

“Delirium” is present if all of the first three are present, and either (4) or (5).

Sources

Diagnostic and Statistical Manual of Mental Disorders. 4th ed. Washington, DC: American Psychiatric Association; 1994:124-133.

“Confusion Assessment Method (CAM) for Delirium.” Inouye, S. Annals of Internal Medicine 1990; 113: 941-8

The copyright of the article Delirium in General Medicine is owned by James Cooper. Permission to republish Delirium in print or online must be granted by the author in writing.