Classification and external resources
ICD-10 F05
ICD-9 293.0
DiseasesDB 29284
eMedicine med/3006
MeSH D003693

Delirium or acute confusional state is a common and severe neuropsychiatric syndrome with core features of acute onset and fluctuating course, attentional deficits and generalized severe disorganization of behavior. It typically involves other cognitive deficits, changes in arousal (hyperactive, hypoactive, or mixed), perceptual deficits, altered sleep-wake cycle, and psychotic features such as hallucinations and delusions. It is often caused by a disease process outside the brain, such as infection (urinary tract infection, pneumonia) or drug effects, particularly anticholinergics or other CNS depressants (benzodiazepines and opioids).[1] Although hallucinations and delusions are sometimes present, these are not required for the diagnosis, and the symptoms of delirium are clinically distinct from those induced by psychosis or hallucinogens (with the exception of deliriants.)

Delirium itself is not a disease, but rather a clinical syndrome (a set of symptoms), which result from an underlying disease or new problem with mentation. Like its components (inability to focus attention, mental confusion and various impairments in awareness and temporal and spatial orientation), delirium is simply the common symptomatic manifestation of early brain or mental dysfunction (for any reason). Without careful assessment, delirium can easily be confused with a number of psychiatric disorders because many of the signs and symptoms are conditions present in dementia, depression, and psychosis.[2]

Treatment of delirium requires treatment of the underlying causes. In some cases, temporary or palliative or symptomatic treatments are used to comfort patients or to allow better patient management (for example, a patient who, without understanding, is trying to pull out a ventilation tube that is required for survival). Delirium is probably the single most common acute disorder affecting adults in general hospitals. It affects 10-20% of all hospitalized adults, and 30-40% of elderly hospitalized patients and up to 80% of ICU patients.[3]



In common usage, delirium is often used to refer to drowsiness, disorientation, and hallucination. In broader medical terminology, however, a number of other symptoms, including a sudden inability to focus attention, and even (occasionally) sleeplessness and severe agitation and irritability, also define "delirium," and hallucination, drowsiness, and disorientation are not required.

There are several medical definitions of delirium (including those in the DSM-IV and ICD-10). However, all include some core features.

The core features are:

  • Disturbance of consciousness (that is, reduced clarity of awareness of the environment, with reduced ability to focus, sustain, or shift attention)
  • Change in cognition (e.g., problem-solving impairment or memory impairment) or a perceptual disturbance
  • Onset of hours to days, and tendency to fluctuate.
  • Behaviour may be either overactive or underactive. Sleep is often disturbed.
  • Thinking is slow and muddled but the content is often complex. [4]

Common features also tend to include:

Signs and symptoms

Since delirium may occur in very many grades of severity, all symptoms may occur with varying degrees of intensity. A mild disability to focus attention may result in only a disability in solving the most complex problems. As an extreme example, a mathematician with the flu may be unable to perform creative work, but otherwise may have no difficulty with basic activities of daily living. However, as delirium becomes more severe, it disrupts other mental functions, and may be so severe that it borders on unconsciousness or a vegetative state. In the latter state, a person may be awake and immediately aware and responsive to many stimuli, and capable of coordinated movements, but unable to perform any meaningful mental processing task at all.

Delirium may be of a hyperactive variety manifested by 'positive' symptoms of agitation or combativeness, or it may be of a hypoactive variety (often referred to as 'quiet' delirium) manifested by 'negative' symptoms such as inability to converse or focus attention or follow commands. While the common non-medical view of a delirious patient is one who is hallucinating, most people who are medically delirious do not have either hallucinations or delusions. Delirium is commonly associated with a disturbance of consciousness (e.g., reduced clarity of awareness of the environment). The change in cognition (memory deficit, disorientation, language disturbance) or the development of a perceptual disturbance, must be one that is not better accounted for by a pre-existing, established, or evolving dementia. Usually the rapidly fluctuating time course of delirium is used to help in the latter distinction.[5]


The delirium-sufferer loses the capacity for clear and coherent thought. This may be apparent in disorganised or incoherent speech, the inability to concentrate (focus attention), or in a lack of any goal-directed thinking. These limitations in thought may also be manifested as purposeless behavior, such as rummaging or punding, or as a difficulty completing a single purpose-oriented task - to the extent that a delirious individual may engage in a string of incomplete and unrelated activities.

Disorientation (another symptom of confusion, and usually a more severe one) describes the loss of awareness of the surroundings, environment and context in which the person exists. It may also appear with delirium, but it is not required, as noted. Disorientation may occur in time (not knowing what time of day, day of week, month, season or year it is), place (not knowing where one is) or person (not knowing who one is).

Cognitive function may be impaired enough to make medical criteria for delirium, even if orientation is preserved. Thus, a patient who is fully aware of where they are and who they are, but cannot think because they cannot concentrate, may be medically delirious. The state of delirium most familiar to the average person is that which occurs from extremes in pain, lack of sleep, or emotional shock.

Because most high level mental skills are required for problem solving, including ability to focus attention, this ability also suffers in delirium. However, this is a secondary phenomenon, since problem-solving involves many sub-skills and basic mental abilities, any of which may be impaired in a delirious patient.

Memory formation

Impairments to cognition may include temporary reduction in the ability to form short-term or long-term memory. Difficult short-term memory tasks like ability to repeat a phone number may be continuously disrupted during a delirium, but easier short-term memory tasks like repeating single words, or remembering simple questions long enough to give an answer, may not be impaired. Reduction in formation of new long-term memory (which by definition survive withdrawal of attention), is common in delirium, because initial formation of (new) long-term memories generally requires an even higher degree of attention, than do short-term memory tasks. Since older memories are retained without need of concentration, previously formed long-term memories (i.e., those formed before the period of delirium) are usually preserved in all but the most severe cases of delirium (and when destroyed, are destroyed by the underlying brain pathology, not the delirious state per se).

Awareness and affect

Hallucinations (perceived sensory experience with the lack of an external source) or distortions of reality may occur in delirium, but they are not essential for the diagnosis. Commonly these are visual distortions, and can take the form of masses of small crawling creatures (particularly common in delirium tremens, caused by severe alcohol withdrawal) or distortions in size or intensity of the surrounding environment.

Strange beliefs may also be held during a delirious state, but these are not considered fixed delusions in the clinical sense as they are considered too short-lived (i.e., they are temporary delusions - such as thinking that a nurse is a person from his/her past trying to cause injury). Interestingly, in some cases sufferers may be left with false or delusional memories after delirium, basing their memories on the confused thinking or sensory distortion which occurred during the episode of delirium. Other instances would be inability to distinguish reality from dreams.

Abnormalities of affect which may attend the state of delirium may include many distortions to perceived or communicated emotional states. Emotional states may also fluctuate, so that a delirious person may rapidly change between, for example, terror, sadness and jocularity.


The duration of delirium is typically affected by the underlying cause. If caused by a fever, the delirious state often subsides as the severity of the fever subsides. However, it has long been suspected that in some cases delirium persists for months and that it may even be associated with permanent decrements in cognitive function. Barrough said in 1583 that if delirium resolves, it may be followed by a "loss of memory and reasoning power." Recent studies bear this out, with cognitively normal patients who suffer an episode of delirium carrying an increased risk of dementia in the years that follow. In many such cases, however, delirium undoubtedly does not have a causal nature, but merely functions as a temporary unmasking with stress, of a previously unsuspected (but well-compensated) state of minimal brain dysfunction (early dementia).


Delirium is a very general and nonspecific symptom of organ dysfunction, where the organ in question is the brain. Delirium may be caused by physical illness, which can be mild, or any process which interferes with the normal metabolism or function of the brain. For example, electric shock, fever, pain, poisons (including toxic drug reactions), brain injury, hypoxia, anoxia, surgery, traumatic shock, lack of food or water or sleep, and even withdrawal symptoms of certain drug and alcohol dependent states, are all known to cause delirium. In addition, there is an interaction between acute and chronic symptoms of brain dysfunction; delirious states are more easily produced in people already suffering with underlying chronic brain dysfunction.[6]

Critical illness

The most common behavioral manifestation of acute brain dysfunction is delirium, which occurs in up to 60% to 80% of mechanically ventilated medical and surgical ICU patients and 50% to 70% of non-ventilated medical ICU patients.[6] During the ICU stay, acute delirium is associated with complications of mechanical ventilation including nosocomial pneumonia, self-extubation, and reintubation.[3] ICU delirium predicts a 3- to 11-fold increased risk of death at 6 months even after controlling for relevant covariates such as severity of illness.[3] Of late, delirium has been recognized by some as a sixth vital sign, and it is recommended that delirium assessment be a part of routine ICU management.[7] The elderly may be at particular risk for this spectrum of delirium and dementia.[7] A firm understanding of the pathophysiologic mechanisms of delirium remains elusive despite improved diagnosis and potential treatments.

Substance withdrawal

Drug withdrawal is a common cause of delirium. The most notable are alcohol withdrawal and benzodiazepine withdrawal but other drug withdrawals both from licit and illicit drugs can sometimes cause delirium.

Gross structural brain disorders

  • Head trauma (i.e., concussion, traumatic bleeding, penetrating injury, etc.)
  • Gross structural damage from brain disease (stroke, spontaneous bleeding, tumor, etc.)

Neurological disorders




  • Medications including psychotropic medications, opiates and benzodiazepines.[1]


Mental illness

Some mental illnesses, such as mania, or some types of acute psychosis, may cause a rapidly fluctuating impairment of cognitive function and ability to focus. However, they are not technically causes of delirium, since any fluctuating cognitive symptoms that occur as a result of these mental disorders are considered by definition to be due to the mental disorder itself, and to be a part of it. Thus, physical disorders can be said to produce delirium as a mental side-effect or symptom, although primary mental disorders which produce the symptom cannot be put into this category once identified. However, such symptoms may be impossible to distinguish clinically from delirium resulting from physical disorders, if a diagnosis of an underlying mental disorder has yet to be made.[citation needed]


Differential points from other processes and syndromes that cause cognitive dysfunction:

  • Delirium may be distinguished from psychosis, in which consciousness and cognition may not be impaired (however, there may be overlap, as some acute psychosis, especially with mania, is capable of producing delirium-like states).
  • Delirium is distinguished from dementia (chronic organic brain syndrome) which describes an "acquired" (non-congenital) and usually irreversible cognitive and psychosocial decline in function. Dementia usually results from an identifiable degenerative brain disease (for example Alzheimer disease or Huntington's disease). Dementia is usually not associated with a change in level of consciousness, and a diagnosis of dementia requires a chronic impairment.
  • Delirium is distinguished from depression.
  • Delirium is distinguished by time-course from the confusion and lack of attention which result from long term learning disorders and varieties of congenital brain dysfunction. Delirium has also been referred to as 'acute confusional state' or 'acute brain syndrome'. The key word in both of these descriptions is "acute" (meaning: of recent onset), since delirium may share many of the clinical (i.e., symptomatic) features of dementia, developmental disability, or attention-deficit hyperactivity disorder, with the important exception of symptom duration.
  • Delirium is not the same as confusion, although the two syndromes may overlap and be present at the same time. However, a confused patient may not be delirious (an example would be a stable, demented person who is disoriented to time and place), and a delirious person may not be confused (for example, a person in severe pain may not be able to focus attention because of the pain, and thus by definition delirious, but may be completely oriented and not at all confused).

It is a corollary of the above differential criteria that a diagnosis of delirium cannot be made without a previous assessment, or knowledge, of the affected person's baseline level of cognitive function. In other words, a mentally disabled or demented person who is operating at their own baseline level of mental ability might appear to be delirious without a baseline functional status against which to compare.

Several valid and reliable rating scales now exist which can be used to accurately diagnose delirium by trained individuals.[8][9]


Episodes of delirium can be prevented by identifying hospitalized people at risk of the condition: those over 65, those with a known cognitive impairment, those with hip fracture, those with severe illness.[10] Close observation for the early signs is recommended in those people. Systematically addressing the common contributing factors (such as constipation, dehydration and polypharmacy), as well as providing adequate lighting, signage and ways to tell the time, may prevent delirium.[10][11]

It is thought that 30–40% of all cases of delirium could be prevented, and that high rates of delirium reflect negatively on the quality of care.[11]


Treatment of delirium involves two main strategies. First, treatment of the underlying presumed acute cause or causes. Second, optimising conditions for the brain. This involves ensuring that the patient with delirium has adequate oxygenation, hydration, nutrition, and normal levels of metabolites, that drug effects are minimised, constipation treated, pain treated, and so on. Detection and management of mental stress is also very important. Thus, the traditional concept that the treatment of delirium is 'treat the cause' is not adequate; patients with delirium actually require a highly detailed and expert analysis of all the factors which might be disrupting brain function.

Non-pharmacological treatments are the first measure in delirium, unless there is severe agitation that places the person at risk of harming oneself or others. Avoiding unnecessary movement, involving family members, having recognizable faces at the bedside, having means of orientation available (such as a clock and a calendar) may be sufficient in stabilizing the situation.[10][11] If this is insufficient, verbal and non-verbal de-escalation techniques may be required to offer reassurances and calm the person experiencing delirium.[10] Only if this fails, or if de-escalation techniques are inappropriate, is pharmacological treatment indicated.[10][11]

The pharmacological treatment for delirium depends on its cause. Antipsychotics, particularly haloperidol, are the most commonly used drugs for delirium and the most studied.[10][11] Evidence is weaker for the atypical antipsychotics, such as risperidone, olanzapine and quetiapine.[11][12] British professional guidelines by the National Institute for Health and Clinical Excellence advise haloperidol or olanzapine.[10]

Benzodiazepines themselves can cause delirium or worsen it,[11] and lack a reliable evidence base.[13] However, if delirium is due to alcohol withdrawal or benzodiazepine withdrawal or if antipsychotics are contraindicated (e.g. in Parkinson's disease or neuroleptic malignant syndrome), then benzodiazepines are recommended.[11] Similarly, people with dementia with Lewy bodies may have significant side-effects to antipsychotics, and should either be treated with a small dose or not at all.[10]

The antidepressant trazodone is occasionally used in the treatment of delirium, but it carries a risk of oversedation, and its use has not been well studied.[11]


The highest prevalence of delirium (often 50% to 75% of patients) is generally seen in critically ill patients in the intensive care unit or ICU (which used to be referred to by the misnomers "ICU psychosis" or "ICU syndrome", terms largely abandoned for the more widely accepted and scientifically supported term delirium). Since the advent of validated and easy to implement delirium instruments for ICU patients such as the Confusion Assessment Method for the ICU (CAM-ICU)[8] and the Intensive Care Delirium Screening Checkllist (IC-DSC).[9] Of the hundreds of thousands of ICU patients develop delirium in ICUs every year, it has been recognized that most of them being of the hypoactive variety that is easily missed and invisible to the managing teams unless actively monitored using such instruments. The causes of delirium in such patients depend on the underlying illnesses, new problems like sepsis and low oxygen levels, and the sedative and pain medicines that are nearly universally given to all ICU patients. Outside the ICU, on hospital wards and in nursing homes, the problem of delirium is also a very important medical problem, especially for older patients. The most recent area of the hospital in which delirium is just beginning to be monitored routinely in many centers is the Emergency Department.

A systematic review of delirium in general medical inpatients showed that estimates of delirium prevalence on admission ranged from 10 to 31%.[14]

Society and culture

Delirium is one of the oldest forms of mental disorder known in medical history.[15]

Sims (1995, p. 31) points out a "superb detailed and lengthy description" of delirium in The Stroller's Tale from Charles Dickens' The Pickwick Papers.[16][17]

See also


  1. ^ a b Clegg, A; Young, JB (2011 Jan). "Which medications to avoid in people at risk of delirium: a systematic review.". Age and ageing 40 (1): 23–9. doi:10.1093/ageing/afq140. PMID 21068014. 
  2. ^ Gleason OC (March 2003). "Delirium". Am Fam Physician 67 (5): 1027–34. PMID 12643363. 
  3. ^ a b c Ely EW, Shintani A, Truman B, et al. (2004). "Delirium as a predictor of mortality in mechanically ventilated patients in the intensive care unit". JAMA 291 (14): 1753–62.. doi:10.1001/jama.291.14.1753. PMID 15082703. 
  4. ^ Gelder, Mayou, Geddes (2005). Psychiatry. (Pg.138) New York, NY: Oxford University Press Inc.
  5. ^ "Delirium - Cleveland Clinic". Retrieved 2007-06-11. 
  6. ^ a b Gunther ML, Jackson JC, Ely EW (July 2007). "The cognitive consequences of critical illness: practical recommendations for screening and assessment". Crit Care Clin 23 (3): 491–506. doi:10.1016/j.ccc.2007.07.001. PMID 17900482. 
  7. ^ a b Flaherty JH, Rudolph J, Shay K, et al. (2007). "Delirium is a serious and under-recognized problem: why assessment of mental status should be the sixth vital sign". J Am Med Dir Assoc 8 (5): 273–5.. doi:10.1016/j.jamda.2007.03.006. PMC 2645654. PMID 17234820. 
  8. ^ a b Ely EW, Inouye SK, Bernard GR, et al. (December 2001). "Delirium in mechanically ventilated patients: validity and reliability of the confusion assessment method for the intensive care unit (CAM-ICU)". JAMA 286 (21): 2703–10. doi:10.1001/jama.286.21.2703. PMID 11730446. 
  9. ^ a b Bergeron N, Dubois MJ, Dumont M, Dial S, Skrobik Y (May 2001). "Intensive Care Delirium Screening Checklist: evaluation of a new screening tool". Intensive Care Med 27 (5): 859–64. doi:1007/s001340100909. PMID 11430542. 
  10. ^ a b c d e f g h National Institute for Health and Clinical Excellence. Clinical guideline 103: Delirium. London, 2010.
  11. ^ a b c d e f g h i Inouye SK (March 2006). "Delirium in older persons". N. Engl. J. Med. 354 (11): 1157–65. doi:10.1056/NEJMra052321. PMID 16540616. 
  12. ^ Tyrer, Peter; Silk, Kenneth R., eds (24 January 2008). "Delirium". Cambridge Textbook of Effective Treatments in Psychiatry (1st ed.). Cambridge University Press. pp. 175–184. ISBN 978-0521842280. 
  13. ^ Lonergan E, Luxenberg J, Areosa Sastre A, Wyller TB (2009). "Benzodiazepines for delirium". Cochrane Database Syst Rev (1): CD006379. doi:10.1002/14651858.CD006379.pub2. PMID 19160280. 
  14. ^ Siddiqi, N. (30 June 2006). "Occurrence and outcome of delirium in medical in-patients: a systematic literature review". Age and Ageing 35 (4): 350–364. doi:10.1093/ageing/afl005. 
  15. ^ Berrios GE (November 1981). "Delirium and confusion in the 19th century: a conceptual history". Br J Psychiatry 139: 439–49. doi:10.1192/bjp.139.5.439. PMID 7037094. 
  16. ^ Sims, Andrew (2002). Symptoms in the mind: an introduction to descriptive psychopathology. Philadelphia: W. B. Saunders. ISBN 0-7020-2627-1. 
  17. ^ Dickens, C. (1837) The Pickwick Papers. Available for free on Project Gutenberg.

Further reading

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Look at other dictionaries:

  • Delirium — tremens Pour les articles homonymes, voir Delirium tremens (homonymie). Le delirium tremens est une conséquence neurologique sévère du syndrome de sevrage d alcool. C est un état d agitation avec fièvre, tremblements des membres,onirisme et… …   Wikipédia en Français

  • Delirium — De*lir i*um (d[ e]*l[i^]r [i^]*[u^]m), n. [L., fr. delirare to rave, to wander in mind, prop., to go out of the furrow in plowing; de + lira furrow, track; perh. akin to G. geleise track, rut, and E. last to endure.] 1. (Med.) A state in which… …   The Collaborative International Dictionary of English

  • Delirium — Saltar a navegación, búsqueda Delirium Información personal Origen Málaga, España …   Wikipedia Español

  • delirium — tremens [ delirjɔmtremɛ̃s ] ou delirium [ delirjɔm ] n. m. inv. • 1819; en angl. 1813; mots lat. « délire tremblant » ♦ Didact. Délire aigu accompagné d agitation et de tremblement et qui est particulier aux alcooliques. Un accès de delirium… …   Encyclopédie Universelle

  • Delirium — Sn Bewußtseinstrübung erw. fach. (16. Jh.) Entlehnung. Entlehnt aus l. dēlīrium Irresein , zu l. dēlīrus wahnsinnig (und l. dēlīrāre wahnsinnig sein; Unsinniges reden, faseln ), das auf einer Zusammenbildung von l. dē līrā (īre), eigentlich von… …   Etymologisches Wörterbuch der deutschen sprache

  • delirium — DELÍRIUM TRÉMENS, s.n. Criză caracterizată prin delir (1), halucinaţii vizuale sau auditive şi tremurături ale feţei şi ale membrelor, care apare la alcoolicii cronici. [pr.: ri um] – cuv. lat. Trimis de LauraGellner, 13.07.2006. Sursa: DEX 98 … …   Dicționar Român

  • DELIRIUM — (бред), термин, употребляемый в русской психиатрической литературе исключительно для обозначения одного из видов расстройств сознания (состояний сно лодобной спутанности), сопровождающихся б. или м. обильными, преимущественно зрительными… …   Большая медицинская энциклопедия

  • Delirium — Delirium, Irrereden, Phantasiren, nennt man ein den äußern Gegenständen und Verhältnissen widersprechendes falsches Denken und Urtheilen, bedingt durch irgend einen idiopathischen oder sympathischen Reizzustand des Gehirns, gewöhnlich mit… …   Herders Conversations-Lexikon

  • delirium — 1590s, from L. delirium madness, from deliriare be crazy, rave, lit. go off the furrow, a plowing metaphor, from phrase de lire, from de off, away (see DE (Cf. de )) + lira furrow, earth thrown up between two furrows, from PIE *leis track, furrow …   Etymology dictionary

  • Delirium — »Bewusstseinstrübung mit Wahnvorstellungen«: Das medizinische Fachwort wurde Ende des 17. Jh.s aus lat. delirium »Persönlichkeitsstörung« entlehnt. Das zugrunde liegende Adjektiv lat. delirus »wahnsinnig« ist von delirare »wahnsinnig sein«… …   Das Herkunftswörterbuch

  • delirium — [di lir′ē əm] n. pl. deliriums or deliria [di lir′ēə] [L, madness < delirare, to rave, lit., to turn the furrow awry in plowing < de , from + lira, a line, furrow: see LIST1] 1. a temporary state of extreme mental excitement, marked by… …   English World dictionary

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