delirium

Psychiatric asPects of general medicine

Deliriummax henderson

Abstractdelirium is a common life-threatening condition, suggestive of global

organic cognitive dysfunction, which is the final common pathway for a

number of insults. inattention is the most common feature but disorienta-

tion, hallucinations, affective changes, and alterations in the sleep–wake

cycle are also seen. the classical picture of the hyperactive wandering

patient is less common than the withdrawn hypoactive presentation.

Psychosis is equally likely in both groups and should be investigated.

many different assessment tools are available to assist in the diagnosis

of delirium, though the most important step is to consider the diagnosis

in the first place. non-pharmacological interventions are vital; their aim

is to minimize the impact of factors which predispose an individual to an

episode of delirium. in established delirium, investigation and manage-

ment of the underlying cause is crucial. most drug treatment involves

the use of antipsychotic medication, although the evidence is limited.

short-acting reversible benzodiazepines specifically target the anxiety

experienced in delirium and thus may be useful if not contraindicated.

Keywords antipsychotics; delirium; hallucinations; hyperactive;

hypoactive; inattention

Definition

Delirium describes an organic brain disorder, often of acute onset, in which multiple domains of cognitive function are disturbed along with changes in levels of arousal and alterations in the sleep–wake cycle.1,2 It commonly follows a fluctuating course. The disturbances in brain activity are secondary to another insult although the nature of the presentation is rarely a reliable indica-tor of the underlying cause.

Delirium should be distinguished from dementia, although cognitive impairment is seen in both, and an underlying demen-tia might be a predisposing factor for delirium.3 Dementia typi-cally has an insidious onset over months or years whilst delirium runs an acute and fluctuating course.4 Attention is often nor-mal in dementia but impaired in delirium. In the early stages of dementia, orientation and working memory are normal and psychosis rarely seen – this is not true for delirium (see also pages 467–470).

Max Henderson MSc MRCP MRCPsych is MRC Research Training Fellow

in the Department of Psychological Medicine at the Institute of

Psychiatry, King’s College London, UK. Competing interests: none

declared.

medicine 36:9 46

Delirium tremens is a particular form of delirium associated with cessation of drinking in those with alcohol dependence syndrome.5 It is distinct from other forms of delirium (see also pages 422–429).

Epidemiology

Delirium is common. Community studies suggest a prevalence of 0.4% in those aged over 18, rising to 13.6% in those over 85 years.6 A higher prevalence is found in hospital studies, typically 10–20%.7 Acute confusion appears especially common in burns units,8 cancer units9 or intensive care units (ICU)10 where up to half of patients may be delirious.

Risk factors

Risk factors for delirium are best understood as either predispos-ing or precipitating (Table 1).11 Predisposing factors affect the

• improved understanding of the independence of the

cognitive, motoric and psychotic aspects of delirium

• increase in the use of atypical antipsychotic medications

although little good-quality evidence to support this so far

• increased use of cholinesterase inhibitors although little

good-quality evidence to support this so far

Risk factors for delirium

Predisposing factors

older age

Pre-existing cognitive function

sensory impiarment

Precipitating factors

Post-operative

drug side effect

new cerebrovascular event

myocardial infarction

infection

• Urinary tract

• respiratory

• meningitis

• osteomyelitis

• endocarditis

hypoxia

metabolic disturbance

• ↑↓ sodium/potassium/calcium

• ↑↓ glucose

terminal illness

constipation

Table 1

What’s new?

3 © 2008 elsevier ltd. all rights reserved.


delirium threshold, i.e. make one more vulnerable to delirium. Precipitating factors are insults which result in someone becom-ing confused.

Clinical features

Delirium is a syndrome with a range of abnormalities including cognitive, perceptual, motor, affective, and sleep disturbances (Table 2).12 The most common feature is inattention, which is a failure to focus or concentrate, present in 97% of cases. The level of inattention correlates with other aspects of cognitive impair-ment, but not other abnormalities, such as motoric state or the presence of psychosis. Disorientation is one of the least com-mon problems, so therefore the Mini Mental State Examination (MMSE)13 is a poor screening tool for delirium (see also pages 393–398).

Hallucinations occur in half of cases but are prominent in only 20%.12 They are most commonly visual or auditory. Para-noid delusions and disordered thinking also occur. Affective disturbances range from manic presentations with high levels of arousal, elation and irritability to an apparently depressive picture with isolative behaviour, poor eye contact and paucity of spontaneous movement. One symptom commonly overlooked is anxiety. The bewildering experiences of the delirious patient can be terrifying. Disturbances, especially reversal, of the sleep–wake cycle are often seen.

Motor disturbance is a prominent feature of delirium. Hyperac-tive delirium is the most easily recognized subtype, characterized by high levels of arousal, restlessness, distractibility and wan-dering. In contrast, the hypoactive subtype includes the ‘face-to- the-wall’ patients with reduced or slowed movement, reduced or absent speech, apparently reduced awareness and apathy.14,15 About 50% of cases are of the hypoactive subtype, and a further 30% present with a mix of both. The hyperactive presentation is the least common. Furthermore there is no association between the motoric subtype and psychosis – the hypoactive patient is just as likely to be hallucinating.12

Assessment

Many episodes of delirium are missed, often because the hypoac-tive presentation does not prompt a consideration of delirium as a differential diagnosis. Hence, the first step is a low threshold for considering the diagnosis. Gentle exploration for the key fea-tures can follow. Impaired attention has been identified as a core feature. This can be assessed using the reverse digit span,16 serial 7s (from 100) or serial 3s (from 20) (Table 3). Assessing attention

Diagnostic criteria for delirium

ICD-10 criteria4

impairment in consciousness or attention

global cognitive impairment

Psychomotor disturbance

sleep–wake cycle disturbance

emotional disturbance

Table 2

medicine 36:9 46

via its impact on memory is also possible – examples include remembering the examiner’s name after 2 minutes or recalling specific objects identified by the examiner.

Standardized instruments can be useful. However, it is vital to be clear whether they have been designed for screening (e.g. Clock Drawing Test17; Table 4), diagnosis (e.g. Confusion Assess-ment Method18) or to assess severity (e.g. Memorial Delirium Assessment Scale19). One simple screening tool is the Clock Drawing Test which has been validated in several settings.20 It is quick, easy and non-threatening, although the physical require-ments limit its use in those with a stroke or motor neurone dis-ease. The Abbreviated Mental Test Score is also widely used.21 The Confusion Assessment Method18 is one of the best validated and most widely used. It is relatively brief, non-threatening and is designed to be used by non-psychiatrists.

Management

PreventionTwo quite different approaches to primary prevention have been reported. The Yale Delirium Prevention Trial was based on the predisposing/precipitating model of causation already described.22 Strategies to optimize the patient’s condition with special attention paid to orientation, hydration, correcting visual and hearing impairment, and minimizing sleep–wake cycle dis-turbance by reducing night-time noise from movement, tele-phones and bleeps reduced the incidence of delirium on the intervention ward by a third.

Kalisvaart attempted a different approach on a high-risk group of patients.23 The severity of delirium was reduced in patients randomized to 1.5 mg haloperidol starting pre-operatively and continuing up to day 3 post-operatively. Furthermore, the length

Tests of attention

Reverse digit spangive the patient a series of numbers, spoken in a consistent

rhythm, and ask the patient to repeat them to you in reverse

order

1-4-6 6-4-1

2-7-4-8 8-4-7-2

3-1-9-2-5 5-2-9-1-3

Serial subtractionask the patient to start at 100 (or 20) and ask the patient to

subtract 7 (or 3), then subtract a further 7 from the result and

so on. record what they actually say

Table 3

Clock drawing test

• give the patient a sheet of paper with a large circle drawn on it

• ask the patient to add in the numbers to create a clock-face

• ask the patient to add the hands so show a time you tell them

• several scoring systems have been described

Table 4



of each episode was on average halved and there was a reduction in the length of hospital stay.

TreatmentThere are two clear and distinct goals for the treatment of delirium: • The identification and correction of the underlying insult. • The amelioration of the worst symptoms of the delirium, so as to make the patient more comfortable until the underlying problem has been resolved.Investigation of the underlying insult should be guided by infor-mation about the individual patient (including current and recent medications), the results of a thorough clinical examination and evidence from previous investigations. The general rule of start-ing with the least invasive investigations still applies (Table 5). When considering symptomatic treatment it should be remem-bered that the patient’s most distressing symptoms may not be the most obvious or the easiest to treat. Drug treatment is not always needed – there is no drug treatment for a wandering patient.

Antipsychotic medications are the most commonly used although there is little evidence to support this. The most recent Cochrane systematic review found only three small studies of sufficient quality.24 One study compared haloperidol, chlorpromazine and lorazepam in patients with HIV and showed a clear advantage for haloperidol.25 However, this is only one study in a very select group and so we need to be aware of risk of over-generalization. Haloperidol is well tolerated with few extrapyramidal side effects at low doses. It is relatively non-sedative, but hypotension can be a problem. More recent studies have used newer atypical anti-psychotics such as risperidone and quetiapine. There is no evi-dence at present that they are more effective.26

Other drug treatments: a number of alternatives to antipsychot-ics may be used. Several authors advocate the use of benzodiaz-epines on the grounds that that they are short-acting, reversible, well tolerated and specifically treat one of the most unpleasant

Possible investigations in delirium

• Urinalysis

○ microscopy

○ culture

• sputum culture

• full blood count

• Urea & electrolytes

• serum calcium

• serum glucose

• liver function tests

• chest X-ray

• ecg

• mri brain

• cardiac ultrasound

• electroencephalogram (eeg)

• lumbar puncture

Table 5

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features of delirium, which is anxiety.27 Others are concerned about the possibility of over-sedation and the paradoxical reac-tion where patients can become more rather than less agitated. There are several case reports of cholinesterase inhibitors such as donepezil and rivastigmine which appear well tolerated. There is insufficient evidence however to recommend them more widely.28

Conclusions

Delirium is a common and distressing condition. A classical presentation is rare and many episodes go undiagnosed and untreated. Improved care must start with the diagnosis being considered more readily. Good evidence exists for the prevention of delirium both by pharmacological and non-pharmacological methods and these should be employed more widely. Treatment should focus on the individual needs of the patient rather than the most prominent symptoms and both antipsychotic and anx-iolytic medications are widely used. ◆

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Practice points

• disorientation is one of the least common problems

• the mini mental state examination (mmse) is a poor

screening tool for delirium

• hypoactive state is more common than hyperactive

• motoric state is not a guide to the presence of psychosis

• the underlying cause should be sought and treated

appropriately

• fear and anxiety are common and are often overlooked yet

easily managed

• drug treatment for the delirium is not always needed – there

is no drug treatment for a wandering patient


delirium

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