Delirium Causes, Symptoms, and Treatment

Authored by , Reviewed by Dr Colin Tidy | Last edited | Meets Patient’s editorial guidelines

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Treatment of almost all medical conditions has been affected by the COVID-19 pandemic. NICE has issued rapid update guidelines in relation to many of these. This guidance is changing frequently. Please visit to see if there is temporary guidance issued by NICE in relation to the management of this condition, which may vary from the information given below.

Synonyms: acute confusional state, acute brain failure, acute organic reaction, postoperative psychosis

Delirium is a clinical syndrome which is difficult to define exactly but involves abnormalities of thought, perception and levels of awareness. It typically is of acute onset and intermittent[1]. Both hypoactive and hyperactive delirium states are recognised and often patients exhibit features of both. Patients may appear confused or 'not with it' when talking to them. Alternatively, it may be their family or carer noticing the confusion.

It is very common - especially in the elderly - and many of these patients subsequently do not return to their baseline function, with some even requiring institutionalisation. It can occur acutely or subacutely and symptoms fluctuate. More disappointing is the realisation that delirium can be avoided in many cases (up to one third), and the lack of awareness is leading to a large amount of morbidity and mortality and a burden on NHS costs.

The terms 'prevalent delirium' and 'incident delirium' are sometimes seen in the literature. Prevalent delirium means that the condition is present on admission, whereas incident delirium occurs during admission.

Important points to remember in delirium
  • Patients are vulnerable.
  • It is a common scenario for errors - eg, missing the diagnosis and poor management; it has the potential to become serious rapidly.
  • Do not assume confusion is due to long-term dementia or mental handicap even in the elderly and those with learning difficulties:
    • It is important to check the previous level of function from relative/carer/home circumstances.
    • If this is not possible, treat as acute confusion until proven otherwise.
  • Always perform a full physical examination, including airway/breathing/circulation and vital signs; however, bear in mind that the patient may not be able to co-operate fully.
  • Always check blood glucose and pulse oximetry (also see 'Investigations', below).

The incidence and prevalence are influenced by the treatment setting, population assessed and method used for estimation of delirium. In general, data suggest an incidence rate of 3% to 42% and prevalence to vary from 5% to 44% amongst hospitalised patients.

A UK study found a prevalence of 20% in adult acute general medical patients[3]. The prevalence is higher in particular clinical groups, such as patients in intensive care units (ICU). It affects up to 50% who have hip fracture and up to 75% in intensive care.

Furthermore, patients with delirium have longer hospital stays and a higher frequency of complications - eg, urinary incontinence, decubitus ulcers and malnutrition[4].

Risk factors for delirium[1, 5]

The following are risk factors which are associated with an increased risk of delirium:

  • Age ≥65 years.
  • Male sex.
  • Pre-existing cognitive deficit - eg, dementia, stroke.
  • Severity of dementia.
  • Severe comorbidity.
  • Previous episode of delirium.
  • Operative factors - eg, type of operation. Hip fracture repairs are more likely to be associated with delirium, as are emergency operations.
  • Certain conditions - burns, AIDS, fractures, infection, low albumin, dehydration.
  • Current hip fracture or severe illness.
  • Drug use (implicated in nearly half of cases) and dependence - eg, benzodiazepines.
  • Substance misuse - eg, alcohol.
  • Extremes of sensory experience - eg, hypothermia or hyperthermia.
  • Visual or hearing problems.
  • Poor mobility.
  • Social isolation.
  • Stress.
  • Terminally ill.
  • Movement to a new environment.
  • ICU admission.
  • Urea/creatinine abnormalities.

Usually a precipitant is required along with risk factors for delirium to occur. Further, the presence of a greater number of risk factors to begin with means that only a small precipitant is necessary to trigger delirium.

  • Acute infections:
  • Prescribed drugs:
    • Benzodiazepines.
    • Analgesics - eg, morphine.
    • Anticholinergics.
    • Anticonvulsants.
    • Anti-Parkinsonism medications.
    • Steroids.
  • Surgical:
    • Postoperative.
  • Toxic substances:
  • Vascular disorders:
  • Metabolic causes:
    • Hypoxia.
    • Electrolyte abnormalities - eg, hyponatraemia and hypercalcaemia.
    • Hypoglycaemia or hyperglycaemia.
    • Hepatic impairment.
    • Renal impairment.
  • Vitamin deficiencies:
  • Endocrinopathies:
    • Hypothyroidism and hyperthyroidism.
    • Hypopituitarism.
    • Hypoparathyroidism or hyperparathyroidism.
    • Cushing's disease.
    • Porphyria.
    • Carcinoid.
  • Trauma:
    • Head injury.
  • Epilepsy:
    • For example, postictally.
  • Neoplasia:
  • Others:
  • Multiple aetiology.
  • Unknown aetiology.

The most common causes are medical conditions such as infections, medications or drug withdrawal.

Making an accurate assessment relies on a collateral history to determine the patient's premorbid level of function. There are very useful cognitive function screening tools - eg, the abbreviated mental test score and the confusion assessment method[1]. The mental tests should be performed regularly and on all high-risk patients. However, it may not be appropriate or possible to do these tests on a sick patient.

The diagnosis of delirium is clinical. The following features may be present:

  • Usually acute or subacute presentation.
  • Fluctuating course.
  • Consciousness is clouded/impaired cognition/disorientation.
  • Poor concentration.
  • Memory deficits - predominantly poor short-term memory.
  • Abnormalities of sleep-wake cycle, including sleeping in the day.
  • Abnormalities of perception - eg, hallucinations or illusions.
  • Agitation.
  • Emotional lability.
  • Psychotic ideas are common but of short duration and of simple content.
  • Neurological signs - eg, unsteady gait and tremor.

Only some of these symptoms may be present. The symptoms may coincide with underlying dementia - which is common.

  • Hypoactive subtype - apathy and quiet confusion are present and easily missed. This type can be confused with depression.
  • Hyperactive subtype - agitation, delusions and disorientation are prominent and it can be confused with schizophrenia.
  • Mixed subtype - patients vary from hypoactive to hyperactive.
  • Check:
    • Airway/breathing/circulation.
    • Conscious level.
    • Vital signs - eg, pulse oximetry, pulse, blood pressure, temperature.
    • Capillary blood glucose.
  • Full cardiovascular and respiratory examination.
  • Full abdominal and genitourinary examination, if appropriate.
  • Full neurological examination.
  • Further examination depending on the suspected problem - eg, ENT or rectal examination.
  • There are several assessment methods available for the diagnosis of delirium. The easiest to use in the primary care setting is the short Confusion Assessment Method (CAM) screening instrument - below. Alternatives include an assessment based on the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria or the 4 'A's test.
  • The CAM criteria for delirium:
    • Confusion that has developed suddenly and fluctuates, and
    • Inattention - ask if the person is easily distracted or has difficulty in focusing attention, and either
    • Disorganised thinking - ask if the person's thinking is disorganised, incoherent, illogical, or unpredictable (for example they have an unclear flow of ideas, change subject unpredictably, or have rambling or irrelevant conversation), or
    • Altered level of consciousness - ask about changes in level of consciousness from alertness to: lethargy (drowsy, easily aroused); stupor (difficult to arouse); comatose (unable to be aroused); or hypervigilant (hyper-alert).

Delirium is commonly mistaken for the following diagnoses:

These should be guided by the clinical presentation and are aimed at identifying an underlying cause of the delirium. Typical investigations that can be performed include:

  • Full history, including collateral history and cognition testing - eg, mini mental state examination.
  • Full examination - look for sources of infection, including the ears and throat; look for rashes, lymphadenopathy and check for constipation.
  • Bloods - include FBC, U&Es and creatinine, glucose, calcium, magnesium, LFTs, TFTs, cardiac enzymes, vitamin B12 levels, syphilis serology, autoantibody screen and PSA. Creatinine is vital to obtain an estimated glomerular filtration rate (eGFR), as this may indicate impaired renal function and affect the handling of medications, and may predispose to drug-induced delirium.
  • Urine dipstick testing and microscopy.
  • Blood cultures and serology, if indicated.
  • ECG.
  • Pulse oximetry and arterial blood gas, if indicated.
  • CXR and possibly abdominal X-ray, if indicated.
  • Further imaging - eg, CT scan of the brain.
  • Lumbar puncture may be necessary.
  • Electroencephalography (EEG) - this is usually only performed if there is doubt regarding the diagnosis.
  • This begins with increased awareness of delirium and regular measures of cognitive function. The underlying cause needs to be treated.
  • It is common for patients with delirium to be admitted to hospital to help investigate the patient and for supportive management. However, some patients can be managed in the community and moving patients to a new environment can worsen delirium.
  • In delirium, the features are fluctuating and some patients are lucid between episodes and can thus provide informed consent during these periods. However, if the patient is not able to provide informed consent then they can be treated in their best interests under common law.
  • If the patient becomes violent or is a danger to themself, it may be possible to manage them initially using verbal and non-verbal de-escalation techniques[7].

But more specific to delirium, the management can be divided into:

  • Supportive management.
  • Environmental measures.
  • Medical management.
  • Management post-discharge.

Supportive management

  • Clear communication.
  • Reminders of the day, time, location and identification of surrounding persons.
  • Have a clock available.
  • Have familiar objects from home around patients, especially glasses, walking aids and hearing aids. Treat impacted earwax and ensure the person has functioning spectacles, or that hearing aids are available and used if needed.
  • Staff consistency - both doctors and nurses.
  • Relaxation - eg, watch television.
  • Involve the family and carers.

Environmental measures

  • Avoid sensory extremes (over- or under-stimulation).
  • Adequate space and sleep; patients should be encouraged to maintain a normal sleep/wake cycle. The use of hypnotics to aid sleep is usually discouraged and these may contribute to delirium. Melatonin has been tried but data are lacking to support its routine use[8]
  • Single rooms if possible.
  • Avoid speciality jargon.
  • Control excess noise.
  • Control room lighting and have a low-wattage bulb at night.
  • Control room temperature (aim for 21-23°C).
  • Use health advocates (interpreters) where needed and if possible.
  • Maintain competence - eg, maintain walking in ambulant patients.
  • Adequate nutrition. Many patients with delirium may not eat as much as usual and will need assistance with their oral intake. Offer foods rich in calories and that are known to be favoured by the patient. Record and monitor the patient's weight, and consider referral to a dietician, based on locally agreed pathways.

A note on managing wandering: the delirious patient may have a tendency to wander. It is common to think of restraining and/or sedating the patient in these circumstances. However, this may only worsen the situation. The management should aim to keep the patient safe, using the least restrictive management - eg, think of causes of agitation or wandering (eg, need for the toilet). These causes should be rectified; if this is not possible, using distraction may help. Relatives or carers may be helpful in this scenario.

Medical management[9]

Correct underlying precipitants including:

  • Infection: whilst infection is a common cause of delirium, it is not the only cause and is not present in all cases. Urinary tract infection, in particular, is commonly over-diagnosed in this scenario.
  • Constipation: many older patients with delirium who do not eat or drink much may become constipated. Laxatives should be prescribed to constipated patients in line with local policy, and taking into account patient preferences - eg, whether they are capable of the volume of liquid necessary for some laxatives.
  • Urinary retention: this is commonly missed in older people. It is not uncommon to still pass urine, and indeed have urinary frequency and urgency, in the presence of significant post-void residual urine volumes. Urinary retention may contribute to agitation. Underlying contributory factors such as constipation, use of anticholinergic drugs and immobility should be addressed. If a catheter is required, it should be used only while the person is unwell, and plans for its removal should be considered part of the process of insertion.
  • Dehydration and electrolyte abnormalities: many (although not all) patients with delirium are dehydrated and a clinical assessment of volume status should be undertaken; this will probably include assessment of postural changes in blood pressure. Severely dehydrated patients or those with hypotension or suspicion of acute kidney injury should have blood tests and usually be referred to secondary care for further assessment. Patients with mild dehydration or who are not currently dehydrated should be encouraged with oral rehydration. This may be achieved by offering fluids and recording intake, aiming for an intake adequate to restore and/or maintain hydration. Another strategy may be to offer small sips of fluids - eg, 60 ml with each interaction with the patient.
  • Pain: regular paracetamol is a part of many multi-component interventions for delirium. A weak opioid should be considered on a prn basis and analgesia titrated to pain, whilst being mindful of common side-effects of opioid analgesia. This means that drugs like tramadol, Oramorph®, buprenorphine and codeine can be useful - but close surveillance will be needed to respond quickly to the possibility of making confusion worse.
  • Medication: consider whether a medication has been stopped or started recently. See below for further information.

Optimise treatment of comorbidities as symptoms caused by sub-optimally managed conditions - eg, COPD or diabetes - may increase agitation.

Pharmacological management

  • Using drugs to treat delirium can lead to adverse effects and worsening of delirium; therefore, careful consideration is required.
  • Antipsychotics have beneficial effects in selected patients, particularly those who are aggressive and do not respond to verbal and non-verbal de-escalation techniques.
  • Haloperidol or olanzapine are preferred, using the lowest possible dose for the shortest possible time (normally a week or less). The dose should be titrated gradually until symptoms are controlled. It should be noted that neither drug has a UK licence for this use so normal considerations regarding the use of unlicensed medicines should apply. Note that both drugs have the potential to cause extrapyramidal side-effects and should be used in caution or avoided altogether in some patients (eg, people with Lewy-body Parkinson's disease).
  • In delirium resulting from alcohol withdrawal (delirium tremens), a benzodiazepine such as diazepam or chlordiazepoxide is preferred. The benzodiazepine is usually used as a reducing course. Large doses may lead to sedation and therefore close observation is required. See also the separate Acute Alcohol Withdrawal and Delirium Tremens article.

Management post-discharge

  • The symptoms of delirium may last longer than the underlying condition.
  • This means that some patients will be discharged with persisting abnormalities.
  • These abnormalities include disorientation, inattention and depression.
  • Families and carers may also need to be supported and given advice and reassurance.

Drug-induced delirium is very common amongst the elderly. Drugs can be the sole cause of delirium in some. Common drug causes of delirium include:

  • Benzodiazepines.
  • Narcotic analgesics.
  • First-generation antihistamines.
  • Antispasmodics.
  • Flouroquinolones.
  • Warfarin.
  • Captopril.
  • Theophylline.
  • Isosorbide dinitrate.
  • Dipyridamole.
  • Furosemide.
  • Lithium.
  • Tricyclic antidepressants.
  • Cimetidine.
  • Anti-arrhythmics.
  • Statins[10].
  • Digoxin.
  • Steroids.
  • Beta-blockers.
  • Over-the-counter medications - eg, liquid medications containing alcohol or chlorphenamine.

The role of medications may be suggested by a temporal relationship between onset of delirium and start of new medication. However, this is not always the case and practitioners need to be aware of this. Medication lists should be thoroughly reviewed in delirium. The exact mechanism of delirium is unclear but it is postulated that central cholinergic pathway blockade is a major factor. This may explain why anticholinergic medications readily lead to delirious states. It may be that this factor along with the pharmacokinetic changes that occur later in life and comorbidities increase the susceptibility of elderly patients to drug-induced delirium.

Management involves stopping the offending drug; however, the actual causal medication is often unknown. In this case, all unnecessary medications should be stopped or doses reduced. These medications can be increased or re-introduced when the patient has improved. Furthermore, it may be prudent to prescribe alternatives to medications with high anticholinergic activity - eg, use of proton pump inhibitors rather than cimetidine.

  • Hospital-acquired infections - eg, Clostridium difficile and meticillin-resistant Staphylococcus aureus (MRSA).
  • Pressure sores.
  • Fractures - eg, femoral or hip fractures from falls.
  • Residual psychiatric and cognitive impairment.
  • Some progress to stupor, coma and eventual death.

A study from the Netherlands of patients in an intensive care unit suggests that short-term delirium has no effect on mortality, whereas delirium persisting for longer than 30 days is associated with a two- to three-fold increase in mortality[11]. Some patients may not recover for months and one third of patients will continue to have delirium. Many patients become institutionalised after delirium[12]. A prospective cohort study in Canada discovered that symptoms of delirium may persist for up to a year after an episode[13]. The same study revealed that there was a worse prognosis if the episode has a protracted inpatient course. Patients with malignancy or HIV also have a worse prognosis[14].

Awareness of high-risk patients and subsequent close observation for delirium with prompt assessment and management can potentially reduce morbidity and mortality.

The National Institute for Health and Care Excellence (NICE) recommends a 'tailored multicomponent intervention package' which consists of the following[1]:

  • Multidisciplinary team approach to the prevention of delirium.
  • Patients should be assessed within 24 hours of admission, making note of factors that may precipitate and worsen delirium.
  • There are various interventions listed in the NICE guidance, based on the identified clinical factors - for example:
    • Cognitive impairment or disorientation - provide appropriate lighting and regularly orientate the person. Promote cognitively stimulating activities and regular visits from people well known to the patient.
    • Hypoxia - identify and correct with the appropriate amount of oxygen.
    • Pain - assess verbally and non-verbally and treat.
    • Medications - should be reviewed on a daily basis and non-essential medication stopped.
    • Other factors include dehydration, constipation, reduced mobility, infection, poor nutrition, sensory impairment and sleep disturbance.

Routine use of antipsychotic medications - eg, haloperidol for prevention of delirium - is not supported by research data[15].

Further reading and references

  • Oh ES, Fong TG, Hshieh TT, et al; Delirium in Older Persons: Advances in Diagnosis and Treatment. JAMA. 2017 Sep 26318(12):1161-1174. doi: 10.1001/jama.2017.12067.

  • Fong TG, Davis D, Growdon ME, et al; The interface between delirium and dementia in elderly adults. Lancet Neurol. 2015 Aug14(8):823-832. doi: 10.1016/S1474-4422(15)00101-5. Epub 2015 Jun 29.

  1. Delirium; NICE Clinical Guideline (July 2010 - last updated March 2019)

  2. Grover S, Avasthi A; Clinical Practice Guidelines for Management of Delirium in Elderly. Indian J Psychiatry. 2018 Feb60(Suppl 3):S329-S340. doi: 10.4103/0019-5545.224473.

  3. Pendlebury ST, Lovett NG, Smith SC, et al; Observational, longitudinal study of delirium in consecutive unselected acute medical admissions: age-specific rates and associated factors, mortality and re-admission. BMJ Open. 2015 Nov 165(11):e007808. doi: 10.1136/bmjopen-2015-007808.

  4. Han JH, Wilson A, Ely EW; Delirium in the older emergency department patient: a quiet epidemic. Emerg Med Clin North Am. 2010 Aug28(3):611-31. doi: 10.1016/j.emc.2010.03.005.

  5. Risk reduction and management of Delirium; A national clinical guideline. Scottish Intercollegiate Guidelines Network (SIGN - March 2019)

  6. Delirium; NICE CKS, March 2021

  7. Violence and aggression: short-term management in mental health, health and community settings; NICE Guideline (May 2015)

  8. Jaiswal SJ, McCarthy TJ, Wineinger NE, et al; Melatonin and Sleep in Preventing Hospitalized Delirium: A Randomized Clinical Trial. Am J Med. 2018 Sep131(9):1110-1117.e4. doi: 10.1016/j.amjmed.2018.04.009. Epub 2018 May 3.

  9. CGA in Primary Care setting; patient presenting with confusion and delirium, British Geriatrics Society, 2019

  10. Redelmeier DA, Thiruchelvam D, Daneman N; Delirium after elective surgery among elderly patients taking statins. CMAJ. 2008 Sep 23179(7):645-52.

  11. Klein Klouwenberg PM, Zaal IJ, Spitoni C, et al; The attributable mortality of delirium in critically ill patients: prospective cohort study. BMJ. 2014 Nov 24349:g6652. doi: 10.1136/bmj.g6652.

  12. Young J, Inouye SK; Delirium in older people. BMJ 2007334:842-846

  13. McCusker J, Cole M, Dendukuri N, et al; The course of delirium in older medical inpatients: a prospective study. J Gen Intern Med. 2003 Sep18(9):696-704.

  14. Gleason OC; Delirium. Am Fam Physician. 2003 Mar 167(5):1027-34.

  15. Oh ES, Needham DM, Nikooie R, et al; Antipsychotics for Preventing Delirium in Hospitalized Adults: A Systematic Review. Ann Intern Med. 2019 Oct 1171(7):474-484. doi: 10.7326/M19-1859. Epub 2019 Sep 3.