Delirium

Introduction

Delirium is an acute, fluctuating disturbance of consciousness, attention and cognition caused by an underlying physical illness, medication, or other precipitant. It is extremely common in hospitalised older people - affecting a substantial proportion of medical and surgical inpatients over 65 at some point in their admission - and is a medical emergency requiring urgent identification of and treatment for its underlying cause, not a primary psychiatric condition to be managed with sedation alone.¹

It matters because delirium is independently associated with increased mortality, longer hospital stay, higher rates of institutionalisation, and an increased long-term risk of dementia - and because it is frequently under-recognised, particularly the hypoactive subtype, meaning the underlying reversible cause goes untreated.

Subtypes

Screening: the 4AT

The 4AT is a rapid, validated bedside screening tool requiring no special training, completed in under 2 minutes, and recommended by NICE and the Royal College of Physicians as the standard initial delirium screen.²

A total score of 4 or above indicates possible delirium, with or without cognitive impairment, and should prompt full clinical assessment. A score of 1-3 suggests possible cognitive impairment without confirmed delirium and also warrants further assessment. Collateral history from family, carers or care home staff on the patient's usual baseline is essential to identify acute change, especially where there is coexisting dementia.

Diagnostic features (DSM-5 framework)

• Disturbance of attention and awareness, developing over a short period (hours to days) and representing an acute change from baseline
• Fluctuation in severity during the course of the day, characteristically
• An additional disturbance in cognition (memory, disorientation, language, perception) not better explained by a pre-existing or evolving dementia
• Evidence from history, examination or investigation that the disturbance is caused by a physiological consequence of another medical condition, substance intoxication/withdrawal, or medication

Predisposing and precipitating factors

Delirium results from the interaction between predisposing vulnerability and a precipitating insult - the more vulnerable the brain, the smaller the insult needed to trigger delirium.

Assessment

• Collateral history establishing baseline cognition and the timeline of change - essential to distinguish delirium from dementia and from an acute-on-chronic presentation
• Full medication review, including recent changes, and specific attention to sedatives, anticholinergics, opioids and any recently stopped drug (withdrawal)
• Examination for a source of infection, signs of dehydration, urinary retention (palpable bladder), faecal loading, and any focal neurology
• Bloods: FBC, U&Es, CRP, glucose, calcium, LFTs, TSH, B12/folate
• Urinalysis and culture - but interpret with caution, since asymptomatic bacteriuria is extremely common in older people and should not be treated as the cause of delirium without other supporting evidence of urinary infection (see red flags below)
• Chest X-ray if respiratory signs or unexplained hypoxia
• CT head if there is new focal neurology, a history of head injury, anticoagulant use, or if there is diagnostic uncertainty about an alternative cause

Management

Treat the underlying cause

The single most important step is identifying and treating the precipitant(s) - the infection, the metabolic derangement, the constipation, the causative drug. Delirium itself has no specific pharmacological cure; management of the confusional state is supportive while the underlying problem resolves.

Non-pharmacological management (first-line)

• Reorientation: clear communication, visible clocks and calendars, familiar objects and, where possible, familiar faces (family involvement is genuinely therapeutic, not just supportive)
• Correct sensory impairment: ensure glasses and hearing aids are worn and working
• Protect the sleep-wake cycle: minimise overnight disturbance, encourage daytime activity and light exposure, avoid unnecessary overnight observations where safely possible
• Consistent staff and environment where feasible, minimising ward moves
• Ensure hydration and nutrition, with assistance if needed
• Encourage mobility as early and as safely as possible, avoiding unnecessary bed rest or physical restraint
• Manage pain proactively, since undertreated pain is a common, correctable contributor

Pharmacological management

Reserved for patients who are a risk to themselves or others, or who are severely distressed, and only after non-pharmacological measures have failed - not used routinely to manage delirium.

Where used in other patients, a low dose of an antipsychotic such as haloperidol or risperidone is chosen, for the shortest possible duration, with regular review - the aim is safety, not sedation to the point of unresponsiveness, which itself increases risk of falls, aspiration and further deconditioning.

Communicating with a delirious patient and their family

Delirium is frightening for patients, who may retain fragmented and distressing memories of the episode afterwards, and alarming for families who see a relative behaving in a way that is completely out of character. How the episode is explained substantially affects both.

• Explain to the family that delirium is a symptom of physical illness, not a psychiatric breakdown or the sudden onset of dementia - this reframing alone relieves a great deal of distress
• Give a realistic timeframe: delirium usually improves as the underlying cause is treated, but resolution takes days to weeks rather than hours, and can fluctuate markedly during recovery
• Involve the family actively - familiar faces, voices and objects are genuinely therapeutic, and relatives are often the best source of collateral information about baseline function
• Do not argue with or attempt to correct delusions or hallucinations - reorient gently and calmly, acknowledging the patient's emotional state rather than debating the content of what they believe
• Debrief the patient afterwards where they are able - explaining what happened helps make sense of frightening fragmentary memories and reduces subsequent distress

Distinguishing delirium, dementia and depression

These three frequently coexist - delirium is common in patients with pre-existing dementia (the combination is sometimes called 'acute on chronic confusion'), and depression can present with pseudo-cognitive impairment. Establishing an accurate baseline from collateral history is the key tool for telling them apart, more so than any single bedside test.

Prevention

Multicomponent prevention programmes - addressing orientation, sleep, hydration, mobility, sensory correction and medication review proactively in at-risk inpatients - reduce delirium incidence by around a third in trial evidence, and are recommended for any older person admitted to hospital who is identified as at risk, not only once delirium has already developed.³

NICE recommends assessing every patient on admission for the risk factors that predict delirium - age 65 or over, known cognitive impairment or dementia, current hip fracture, and severe illness - and delivering a targeted prevention package to those identified.¹

Prognosis

Most delirium resolves with treatment of the underlying cause, though resolution can take days to weeks, and full cognitive recovery is sometimes incomplete, particularly in patients with pre-existing cognitive impairment. Delirium is independently associated with increased mortality, longer admission, higher rates of new care home admission, and an increased long-term risk of developing dementia, even after apparent full recovery - which is why an episode of delirium should prompt follow-up cognitive assessment rather than being treated as a fully closed episode once the acute illness resolves.

Persistent delirium - symptoms continuing beyond the resolution of the acute illness, sometimes for months - is more common than generally appreciated, particularly in frail patients and those with underlying dementia. Its existence is a further argument against the assumption that a patient who is still confused at the point of discharge planning must have unrecognised dementia; they may instead be recovering slowly from delirium, and a definitive cognitive diagnosis should not be made during or immediately after an acute episode.