Delirium, also known as acute brain failure, is an acute syndrome characterized by impaired intellect, awareness and concentration. Typically, the cognitive impairment fluctuates throughout the day. In contrast to dementia, delirium tends to be reversible.
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Terminology
The number of synonyms for delirium is bewildering 6, and includes more modern terms, e.g. acute brain failure, acute brain syndrome, acute brain dysfunction, archaic terms, such as a dysergastic reaction, terms with a more psychiatric flavor, for example, exogenous psychosis, and those from a geriatric perspective, like pseudosenility or subacute befuddlement.
Other synonyms include acute cerebral insufficiency, acute mental status change, acute organic psychosis, acute organic reaction, acute confusional state, acute confusion, acute organic syndrome, agitated confusional state, altered mental status, cerebral insufficiency syndrome, metabolic encephalopathy, reversible cognitive dysfunction, reversible dementia, reversible toxic psychosis, toxic confusional state, toxic delirious reaction, toxic encephalopathy, toxic-metabolic encephalopathy and toxic psychosis.
Delirium is surprisingly often misspelt as delerium 5.
Epidemiology
Delirium is a common condition in hospitals, especially in the greater than 65 years old age bracket. Up to 17% older adults presenting as medical emergencies have delirium 1.
Diagnosis
Delirium is diagnosed on clinical criteria.
Clinical presentation
Delirium is formally defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM 5), by five criteria 8:
impaired attention and awareness
acute onset (hours to days), diurnal fluctuation, clear change from normal functioning
impaired cognitive function, e.g. disordered memory, communicative skills, spatial awareness
unexplained by known neuropsychiatric illness or a suppressed alertness level
disturbance can be linked to a physical illness, medication side-effect or substance toxicity/withdrawal (e.g. alcohol)
Delirium is often subdivided into three main motoric subtypes,
hypoactive
hyperactive
mixed
Hyperactive
aggressive
restless
delusional
hallucinatory
show pronounced psychomotor movements, which tend to lack purpose and are often repetitive, such as fidgeting, tapping fingers, pacing, etc.
Hypoactive
lacking interest in surroundings
lassitude
depressed psychomotor activity
Mixed
alternate between periods of hyperactivity and hypoactivity
Pathology
Etiology
The pathogenesis of delirium is complex and not well understood.
The current science identifies two main phenomena, firstly the importance of a neurotransmitter disturbance, in particular acetylcholine and dopamine. Secondly is that inflammation is key, with cytokines being a central actor.
It is usually a multifactorial syndrome and is especially common on the critical care unit and in postoperative patients 1-4.
Host factors
greater than 65 years old
male gender
pre-existing dementia
previous episodes of delirium
alcohol excess
visual and/or hearing impairment
Acute disease
infection and sepsis
acid-base disturbances
metabolic derangements including of sodium, potassium, glucose, etc.
cardiorespiratory impairment
hypoxia
pain
Iatrogenic/environmental factors
medication, e.g. benzodiazepines, anticholinergics
postoperative
immobility
sleep upset
Radiographic features
Imaging features tend to be those of the contributory conditions.
Treatment and prognosis
The treatment of delirium is difficult, requiring a multipronged multidisciplinary approach.
Delirium has a significant impact on morbidity and mortality, it causes elevated inpatient, 30-day and 6-month mortality. It is associated with a more rapid cognitive deterioration, posttraumatic stress disorder and loss of independence.
History and etymology
Delirium derives from the Latin “de lira,” or “off the tracks.”