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DELIRIUM

Delirium is a derangement of mental function characterized by disturbance of consciousness and impairment of cognition. In contrast to dementia, delirium usually develops over a short period of time, it tends to fluctuate in severity over the course of the day, and it usually resolves with treatment of the underlying causes. This disturbance of consciousness results in reduced awareness of the external environment, and a reduction of the ability to focus, sustain, and shift attention. Cognitive impairments in delirium include disorientation in time and place, memory deficits, and language disturbances. Sensory perception, particularly vision, may also be disturbed, resulting in misinterpretations, illusions, and hallucinations. There may be disruption of the normal sleep-wake cycle, with individuals being drowsy during the day and active at night. The acute mental disturbances of delirium can be very frightening and upsetting for patients, who may respond with agitated and aggressive behavior. In younger adults, an episode of delirium is usually quite dramatic and florid (hyperactive delirium), and its detection and diagnosis is relatively straightforward. By contrast, the mental disturbances in elderly individuals with delirium are often much less obvious, particularly if there is a pre-existing dementia (hypoactive delirium). As a result, it is quite common for delirium in an elderly person to be overlooked by their families, by other carers, and by medical and nursing staff. This is unfortunate because, like pain and fever, delirium is an important nonspecific sign that the patient is physically ill, and requires further investigation to identify the cause. If the individual is very demented or very ill, they may be unable to complain of other symptoms, and delirium may be the first or only sign that something significant is amiss.

Age and delirium

Delirium occurs when the brain receives an external insult powerful enough to disrupt its normal functioning. It can occur at any age, but it is most commonly seen in children and elderly people. In childhood, the brain is vulnerable because it is still developing. In old age, increased vulnerability to delirium is due to factors such as dementia and sensory impairment, which become more common with increasing age. As well as being more vulnerable, elderly people are also more liable to be exposed to the external insults, such as physical illness and medication, that commonly cause delirium. The more vulnerable the individual, the less severe such insults need to be in order to precipitate a delirium. Consequently, the highest rates of delirium are to be found in high-risk populations such as elderly medical, surgical, and psychiatric inpatients. Some elderly patient groups, such as those with hip fractures, appear to be particularly prone to developing delirium. In elderly patients, it is important to distinguish delirium from other mental disorders that occur in old age. This can be difficult, not least because disorders such as dementia and depression are themselves risk factors for delirium, and may be co-morbid with it. A useful rule of thumb is that any sudden worsening of cognitive functioning, particularly if alertness and attention are impaired, should be investigated as delirium until proved otherwise.

Causes

Physical illnesses cause delirium by acutely disrupting the normal metabolism of the nerve cells in the brain. This can come about by reducing the oxygen supply (e.g., cardiac failure, a fall in blood pressure, anemia), by physiological disturbances (e.g., fever, liver or kidney failure, endocrine disorders), by the action of drugs and toxins, and by direct damage (e.g., stroke, head injury). The most common causes of delirium in elderly patients are acute infections (particularly of the chest and urinary tract), and the prescribed drugs that they are taking. Almost any drug can cause delirium in an elderly patient, but some are particularly associated with this problem, either because they act directly on the brain (e.g., tranquilizers, anticonvulsants), or because they are broken down and eliminated less efficiently by the elderly body and so accumulate, or because they have particular modes of action. Drugs with anticholinergic activity are particularly liable to cause delirium, which has led to the suggestion that disturbance of the cholinergic nerve systems in the brain is an important feature of the pathology of delirium. In practice, elderly patients are often taking many drugs, and delirium may occur as a cumulative effect of this polypharmacy rather than it being due to one drug acting alone. It is important to bear in mind that delirium can also be caused by the sudden withdrawal of a drug upon which the patient is physically dependent. The most common drug in this respect is alcohol, although in elderly patients other possibilities, such as opiate analgesics and benzodiazepines, should be considered. Although delirium usually has a physical cause, it is recognized that, in particularly vulnerable individuals, a severe psychological stress such as bereavement, relocation, or extreme sensory deprivation may be sufficient to precipitate it.

Outcome

Traditionally, delirium has been regarded as a transient disorder that terminates with either recovery or death. In the majority of cases, the delirious episode is relatively short, but about one-third of patients have prolonged or recurrent episodes. Delirium is associated with increased short-term mortality in elderly patients, due mainly to the underlying physical illness. However, delirious patients also tend to have longer hospital stays, higher rates of functional decline, and higher rates of discharge to nursing homes. Other complications of delirium include falls and fractures if the patient is hyperactive, and pressure sores if they are hypoactive. Prospective studies show that the prognosis in terms of persistent or recurrent symptoms of delirium is relatively poor in elderly patients. This is probably because those who experience delirium are a vulnerable group more likely to develop the condition whenever they become physically ill. A proportion will also be suffering from a form of dementia, which will increase their vulnerability to delirium as it progresses. It is not known if delirium is itself a risk factor for the development or exacerbation of dementia. The family and other carers should be advised of the risk of future delirium, and educated about the symptoms so that they can recognize it if and when it occurs again.

Clinical management

The most important aspect of the clinical management of delirium is prompt diagnosis and treatment of the underlying cause or (more usually) causes. Sometimes the symptoms and behaviors of the delirium itself may need to be treated. The evidence base for this aspect of management is still very limited, and current approaches are based mainly on accumulated clinical experience. These strategies involve both pharmacological and nonpharmacological approaches. Regarding use of medication, there is always a risk that giving a powerful psychoactive drug to a delirious patient will make the problem worse, so this course of action should only be considered if the associated symptoms and behaviors are distressing or potentially dangerous to the patient and/or others. The drug treatment of delirium in elderly patients is similar to that of younger adults, although it is necessary to start with much lower doses. The drugs most commonly used in the management of delirium are neuroleptics (usually haloperidol), or benzodiazepines (e.g., diazepam, lorazepam, alprazolam) if the patient cannot tolerate a neuroleptic. The effects of the drug and its dosage need to be frequently reviewed, to ensure that it is not having any adverse effects. Once the delirium has resolved, the medication should be reduced and, if possible, discontinued over a period of a few days.

Nonpharmacological interventions in delirium are aimed at reducing the confusing, frightening, and disorienting aspects of the hospital or nursing home environment that aggravate the disorder. There is little evidence to inform the use of these strategies, but features such as good lighting, low noise levels, a visible clock, a window on the outside world, and, in particular, the reassuring presence of personal possessions and familiar individuals such as relatives are all thought to be beneficial. Any invasive intervention, including personal care tasks, should be explained simply, slowly, clearly, and repeatedly before it is carried out. Holding the patient's hand while talking helps to focus their attention, and provides reassurance.

Prevention

Regarding prevention, the aim should be to minimize exposure to the various patient- and hospital-related factors that are known to predispose to delirium in elderly inpatients. The ward environment and routines should aim to avoid unnecessary sensory impairment and sleep deprivation, and support a normal sleep-wake cycle. Nonpharmacological sleep-promotion strategies should be used in preference to hypnotic drugs. It is important to ensure adequate food and fluid intake, and patients should be encouraged to be mobile whenever possible. Careful prescribing is important, avoiding where possible any drugs with known potential to cause delirium, particularly in at-risk individuals such as those with dementia. The drug chart should be regularly reviewed, with the aim of keeping the burden of medication as low as possible. In surgical patients, good pre-, peri-, and postoperative care (especially with regard to blood pressure, oxygenation, pain relief, and infection control) will reduce the risk of postoperative delirium.

JAMES LINDESAY

See also DEMENTIA; DISEASE PRESENTATION; PSYCHIATRIC DISEASE IN RELATION TO PHYSICAL ILLNESS; SURGERY IN ELDERLY PEOPLE.

BIBLIOGRAPHY

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th ed. Washington, D.C.: American Psychiatric Association, 1994.

American Psychiatric Association. Practice Guideline for the Treatment of Patients with Delirium. Washington, D.C.: American Psychiatric Association, 1999.

BYRNE, E. J. Confusional States in Older People. London: Edward Arnold, 1994.

CARLSON, A.; GOTTFRIES, C.; WINBLAD, B.; and ROBERTSSON, B., eds. "Delirium in the Elderly: Epidemiological, Pathogenetic, Diagnostic and Treatment Aspects." Dementia and Geriatric Cognitive Disorders 10 (1999): 305–430.

FRANCIS, J., and KAPOOR, W. N. "Prognosis after Hospital Discharge of Older Medical Patients with Delirium." Journal of the American Geriatrics Society 40 (1992): 601–606.

INOUYE, S. K., and CHARPENTIER, P. A. "Precipitating Factors for Delirium in Hospitalized Elderly Persons. Predictive Model and Interrelationship with Baseline Vulnerability." Journal of the American Medical Association 275 (1996): 852–857.

LEVKOFF, S.; EVANS, D.; LIPTZIN, B.; et al. "Delirium, the Occurrence and Persistence of Symptoms among Elderly Hospitalised Patients." Archives of Internal Medicine 152 (1992): 334–340.

LINDESAY, J.; MACDONALD, A.; and STARKE, I. Delirium in the Elderly. Oxford: Oxford University Press, 1990.

LIPOWSKI, Z. J. Delirium: Acute Confusional States. New York: Oxford University Press, 1990.

ROCKWOOD, K.; COSWAY, S.; CARVER, D.; et al. "The Risk of Dementia and Death Following Delirium." Age and Ageing 28 (1999): 551–556.

RUDBERG, M. A.; POMPEI, P.; FOREMAN, M. D.; ROSS, R. E.; and CASSEL, C. K. "The Natural History of Delirium in Older Hospitalized Patients: A Syndrome of Heterogeneity." Age and Ageing 26 (1997): 169–174.