Essential features of delirium

In order to be able to recognise when a person has developed delirium the following features must be present:

1. The person has reduced awareness of their environment and reduced ability to pay attention or maintain attention to what you are saying to them and what is happening in their immediate environment.
2. The person has memory impairment, disorientation, or is speaking inappropriately.
3. The person’s mental impairment develops over a short period of time (usually hours to days) and tends to vary during the course of the day.

There is evidence from the person’s medical history, clinical examination, or laboratory tests that the mental impairment is caused by a general medical condition, substance intoxication or withdrawal, use of medication(s), exposure to a toxin, or a combination of these factors (1).

From the above features it is important to be aware that delirium can present as a very obvious disturbance in the person’s mental functioning, or in a ‘quiet’ and less noticeable form, where the person is inattentive, lethargic and drowsy. People with dementia are most likely to develop the hyperactive form of delirium (2). Delirium is often the first and only sign of chest and urinary tract infection and myocardial infarction in an older person, so it is vital that nurses are skilled in its detection.

1. American Psychiatric Association. 1994. Diagnostic and Statistical Manual Of Mental Disorders (4th edition). Washington, DC: American Psychiatric Association

2. Edlund, A., Lundstrom, M., Sandberg, O. et al. 2007. Symptom profile of delirium in older people with and without dementia. Journal of Geriatric Psychiatry and Neurology 20(3): 166–171