Mohammed T. Abou-Saleh

Principles and Practice of Geriatric Psychiatry.Editors: Professor John R. M. Copeland, Dr Mohammed T. Abou-Saleh and Professor Dan G. BlazerCopyright & 2002 John Wiley & Sons LtdPrint ISBN 0-471-98197-4 Online ISBN 0-470-84641-035Delirium—An OverviewAndrew F. FairbairnCentre for Health Care of the Elderly, Newcastle upon Tyne, UKDelirium is a state of acute confusion due to an underlyingphysical cause. Associated with the disorder of cognition andattention, there is frequently disturbed psychomotor behaviourand disturbance to the sleep–wake cycle. It is a common feature inthose, particularly older patients, who present as acute medicalemergencies. As a common, potentially highly treatable condition,it is associated with major health care costs. It is also underrecognizedand associated with longer periods of inpatient stay. Itis a recognized mental disorder under the English Mental HealthAct, which has significance in relation to compulsory treatment.Formal diagnostic criteria for delirium were only first introducedin DSM-III. These criteria were further revised for DSM-IV and the criteria for general medical conditions are shown inTable 35.1. DSM-IV critera are also described as more specific fordelirium in relation to substance abuse. The main changes in thecriteria are a general simplification with less emphasis on deficitsof attention and more emphasis on the syndrome developing overa short period of time.Confusion, or cognitive impairment, commonly only occurs inthree conditions, namely delirium, dementia and depression. Twoof the ‘‘3Ds’’ are eminently treatable, therefore it is to be regrettedthat cognitive impairment is primarily associated with dementiaand hence only belatedly recognized as a potentially treatablecondition in the case of this particular chapter’s subject, delirium.The rest of the chapter will discuss incidence and risk factors.There is an expanded section on clinical features and discussion ofassessment scales, neuropathogenesis, appropriate investigationsand treatment.INCIDENCEDelirium occurs in 14–56% of older hospitalized patients 1 .Itislower after elective surgery and higher in acute medical admissions.Patients who have suffered delirium during a hospitaladmission tend to stay in hospital for longer and have greaterrequirements for rehabilitation and require increased home careservices 2 .RISK FACTORSInouye et al. 1 propose a multifactorial model for delirium,including predisposing factors and precipitating factors. Thestudy identifies four predisposing factors for delirium, visualimpairment, severe physical illness, cognitive impairment andblood urea nitrogen (BUN):creatinine ratio i.e. an indicator ofdehydration. Using complex methodology, they identified ahierarchy of precipitating factors, the most significant of whichwere major surgery, stay in intensive care, multiple medicationand sleep deprivation. Their conclusion was that the aetiology ofdelirium is multifactorial, but that certain predisposing factors,combined with a weighting of precipitating factors can make thelikelihood of delirium much more predictable. Elie et al. 3 similarlyidentified risk factors that included dementia, advanced age andmedical illness. Robertsson et al. 4 looked at the likelihood that apre-existing dementia could predispose to the onset of deliriumand showed that late-onset Alzheimer’s disease was more likely todo so than early-onset Alzheimer’s disease and that vasculardementia was more likely to do so than early-onset Alzheimer’sdisease.CLINICAL FEATURESWhilst DSM-IV attempts to define the clinical features, it is worthremembering that Lipowski 5 has regularly warned about thesubtle ‘‘prodromal, non-specific’’ features that can even precedethe more formal syndrome. This can be as simple as increasedanxiety or subtle levels of agitation. The cardinal feature isprobably a relatively sudden change in cognition but there canalso be perceptual disturbances. Patients can latterly describegreat difficulties in differentiating between reality and hallucination.Visual hallucinations are classically more common thanauditory hallucinations and are generally unpleasant andfrightening. Thinking is disorganized, slowed and impoverished.Memory is impaired across the entire spectrum of registration,retention and recall. Short-term memory may well be impaired,secondary to poor attention, and patients may be inclined toconfabulate.The impact of delirium on psychomotor behaviour is variable.Some delirious patients will become agitated, restless andhypervigilant. In contrast, some patients will become withdrawn,with slowed physical responses. Finally, the picture of psychomotoractivity can be mixed with oscillation between hyper- andhypo-activity.Having described the classic clinical features above, it should beremembered that Treloar and McDonald 6 have placed emphasison the ‘‘quiet syndrome’’. They argue that one of the reasons thatdelirium is under-recognized is because of the frequency of thehypo-active type of syndrome. There is evidence that nurses arebetter than doctors at identifying the syndrome of delirium andthere is tentative evidence that different aetiologies may possiblyaccount for differentiation in the clinical picture. Zou et al. 7showed that diagnosis by a nurse clinician using a standardizedrating scale (the Confusion Assessment method) and multiplePrinciples and Practice of Geriatric Psychiatry, 2nd edn. Edited by J. R. M. Copeland, M. T. Abou-Saleh and D. G. Blazer&2002 John Wiley & Sons, Ltd