Delirium (formerly acute confusional state, an ambiguous term that is now discouraged) is a specific state of acute confusion attributable to the direct physiological consequence of a medical condition, effects of a psychoactive substance, or multiple causes, which usually develops over the course of hours to days. As a syndrome, delirium presents with disturbances in attention, awareness, and higher-order cognition. People with delirium may experience other neuropsychiatric disturbances including changes in psychomotor activity (e.g., hyperactive, hypoactive, or mixed level of activity), disrupted sleep–wake cycle, emotional disturbances, disturbances of consciousness, or altered state of consciousness, as well as perceptual disturbances (e.g., hallucinations and delusions), although these features are not required for diagnosis.
Diagnostically, delirium encompasses both the syndrome of acute confusion and its underlying organic process, known as an acute encephalopathy. The cause of delirium may be either a disease process inside the brain or a process outside the brain that nonetheless affects the brain. Delirium may be the result of an underlying medical condition (e.g., infection or hypoxia), side effect of a medication such as diphenhydramine, promethazine, and dicyclomine, substance intoxication (e.g., opioids or hallucinogenic deliriants), substance withdrawal (e.g., alcohol or sedatives), or from multiple factors affecting one's overall health (e.g., malnutrition, pain, etc.). In contrast, the emotional and behavioral features due to primary psychiatric disorders (e.g., as in schizophrenia, bipolar disorder) do not meet the diagnostic criteria for 'delirium'.
Delirium may be difficult to diagnose without first establishing a person's usual mental function or 'cognitive baseline'. Delirium may be confused with multiple psychiatric disorders or chronic organic brain syndromes because of many overlapping signs and symptoms in common with dementia, depression, psychosis, etc. Delirium may occur in persons with existing mental illness, baseline intellectual disability, or dementia, entirely unrelated to any of these conditions. Delirium is often confused with schizophrenia, psychosis, organic brain syndromes, and more, because of similar signs and symptoms of these disorders.
Treatment of delirium requires identifying and managing the underlying causes, managing delirium symptoms, and reducing the risk of complications. In some cases, temporary or symptomatic treatments are used to comfort the person or to allow other care (e.g., preventing people from pulling out a breathing tube). Antipsychotics are not supported for the treatment or prevention of delirium among those who are in hospital; however, they may be used in cases where a person has distressing experiences such as hallucinations or if the person poses a danger to themselves or others. When delirium is caused by alcohol or sedative-hypnotic withdrawal, benzodiazepines are typically used as a treatment. There is evidence that the risk of delirium in hospitalized people can be reduced by non-pharmacological care bundles (see ). According to the text of DSM-5-TR, although delirium affects only 1–2% of the overall population, 18–35% of adults presenting to the hospital will have delirium, and delirium will occur in 29–65% of people who are hospitalized. Delirium occurs in 11–51% of older adults after surgery, in 81% of those in the ICU, and in 20–22% of individuals in nursing homes or post-acute care settings. Among those requiring critical care, delirium is a risk factor for death within the next year.
Because of the confusion caused by similar signs and symptoms of delirium with other neuropsychiatric disorders like schizophrenia and psychosis, treating delirium can be difficult, and might even cause death of the patient due to being treated with the wrong medications.
Definition In common usage, delirium can refer to drowsiness, agitation, disorientation, or hallucinations. In medical terminology, however, the core features of delirium include an acute disturbance in attention, awareness, and global cognition.
Although slight differences exist between the definitions of delirium in the DSM-5-TR and ICD-10, the core features are broadly the same. In 2022, the American Psychiatric Association released the fifth edition text revision of the DSM (DSM-5-TR) with the following criteria for diagnosis: A. Disturbance in attention and awareness. This is a required symptom and involves easy distraction, inability to maintain attentional focus, and varying levels of alertness. B. Onset is acute (from hours to days), representing a change from baseline mentation and often with fluctuations throughout the day C. At least one additional cognitive disturbance (in memory, orientation, language, visuospatial ability, or perception) D. The disturbances (criteria A and C) are not better explained by another neurocognitive disorder E. There is evidence that the disturbances above are a "direct physiological consequence" of another medical condition, substance intoxication or withdrawal, toxin, or various combinations of causes
Signs and symptoms Delirium exists across a range of arousal levels, either as a state between normal wakefulness/alertness and coma (hypoactive) or as a state of heightened psychophysiological arousal (hyperactive). It can also alternate between the two (mixed level of activity). While requiring an acute disturbance in attention, awareness, and cognition, the syndrome of delirium encompasses a broad range of additional neuropsychiatric disturbances. Inattention: A disturbance in attention is required for delirium diagnosis. This may present as an impaired ability to direct, focus, sustain, or shift attention. Memory impairment: The memory impairment that occurs in delirium is often due to an inability to encode new information, largely as a result of having impaired attention. Older memories already in storage are retained without need of concentration, so previously formed long-term memories (i.e., those formed before the onset of delirium) are usually preserved in all but the most severe cases of delirium, though recall of such information may be impaired due to global impairment in cognition. Disorientation: A person may be disoriented to self, place, or time. Additionally, a person may be 'disoriented to situation' and not recognize their environment or appreciate what is going on around them. Disorganized thinking: Disorganized thinking is usually noticed with speech that makes limited sense with apparent irrelevancies, and can involve poverty of speech, loose associations, perseveration, tangentiality, and other signs of a formal thought disorder. Language disturbances: Anomic aphasia, paraphasia, impaired comprehension, agraphia, and word-finding difficulties all involve impairment of linguistic information processing. Sleep/wake disturbances: Sleep disturbances in delirium reflect disruption in both sleep/wake and circadian rhythm regulation, typically characterized by fragmented sleep or even sleep-wake cycle reversal (i.e., active at night, sleeping during the day), including as an early sign preceding the onset of delirium. Psychotic and other erroneous beliefs: Symptoms of psychosis include suspiciousness, overvalued ideation and frank delusions. Delusions are typically poorly formed and less stereotyped than in schizophrenia or Alzheimer's disease. They usually relate to persecutory themes of impending danger or threat in the immediate environment (e.g., being poisoned by nurses). Perceptual disturbances: These can include illusions, which involve the misperception of real stimuli in the environment, or hallucinations, which involve the perception of stimuli that do not exist. Mood lability: Distortions to perceived or communicated emotional states as well as fluctuating emotional states can manifest in delirium (e.g., rapid changes between terror, sadness, joking, fear, anger, and frustration). Motor activity changes: Delirium has been commonly classified into psychomotor subtypes of hypoactive, hyperactive, and mixed level of activity, though studies are inconsistent as to their prevalence. Hypoactive cases are prone to non-detection or misdiagnosis as depression. A range of studies suggests that motor subtypes differ regarding underlying pathophysiology, treatment needs, functional prognosis, and risk of mortality, though inconsistent subtype definitions and poorer detection of hypoactive subtypes may influence the interpretation of these findings. The notion of unifying hypoactive and hyperactive states under the construct of delirium is commonly attributed to Lipowski. Hyperactive symptoms include hyper-vigilance, restlessness, fast or loud speech, irritability, combativeness, impatience, swearing, singing, laughing, uncooperativeness, euphoria, anger, wandering, easy startling, fast motor responses, distractibility, tangentiality, nightmares, and persistent thoughts (hyperactive sub-typing is defined with at least three of the above). Hypoactive symptoms include decreased alertness, sparse or slow speech, lethargy, slowed movements, staring, and apathy. Mixed level of activity describes instances of delirium where activity level is either normal or fluctuating between hyperactive and hypoactive.
Causes Delirium arises through the interaction of a number of predisposing and precipitating factors.
Individuals with multiple and/or significant predisposing factors are at high risk for an episode of delirium with a single and/or mild precipitating factor. Conversely, delirium may only result in low risk individuals if they experience a serious or multiple precipitating factors. These factors can change over time, thus an individual's risk of delirium is modifiable (see ).
Predisposing factors Important predisposing factors include the following: 65 or more years of age Cognitive impairment/dementia Physical morbidity (e.g., biventricular failure, cancer, cerebrovascular disease) Psychiatric morbidity (e.g., depression) Sensory impairment (i.e., vision and hearing) Functional dependence (e.g., requiring assistance for self-care or mobility) Dehydration/malnutrition Substance use disorder, especially alcohol use disorder and anticholinergic abuse.
Precipitating factors
Any serious, acute biological factor that affects neurotransmitter, neuroendocrine, or neuroinflammatory pathways can precipitate an episode of delirium in a vulnerable brain. Certain elements of the clinical environment have also been associated with the risk of developing delirium. Some of the most common precipitating factors are listed below: Prolonged sleep restriction or deprivation Environmental, psychophysiological stress (as found in acute care settings) Inadequately controlled pain Immobilization, use of physical restraints Urinary retention, use of bladder catheter Emotional stress Severe constipation/fecal impaction Medications and other drugs, causing substance-induced delirium. This type of delirium is separate from the delirium in elderly and older people above 65 years of age, and is characterized by shorter duration (usually several hours), and the symptoms are highly influenced by the type of drug and amount consumed. Sedatives (benzodiazepines, opioids), anticholinergics, dopaminergics, corticosteroids, polypharmacy General anesthetic Substance intoxication or withdrawal Primary neurologic conditions Severe drop in blood pressure, relative to the person's normal blood pressure (orthostatic hypotension) resulting in inadequate blood flow to the brain (cerebral hypoperfusion) Stroke/transient ischemic attack(TIA) Intracranial bleeding Meningitis, encephalitis Concurrent illness Infections – especially respiratory (e.g. pneumonia, COVID-19) and urinary tract infections Iatrogenic complications Hypoxia, hypercapnea, anemia