Postoperative delirium

What it is

Postoperative delirium is an acute, fluctuating disturbance of attention and awareness, with disorganised thinking or an altered level of consciousness, that begins in the days after surgery, usually within the first three to five days. It is common after major surgery in older patients, especially after hip fracture and cardiac surgery, and it is linked to longer stays, falls, loss of independence, admission to care homes, later cognitive decline and death. Delirium results from a vulnerable brain meeting a precipitating insult. Predisposing factors include older age, dementia or cognitive impairment, frailty, poor vision or hearing, depression, alcohol misuse and many medicines. Precipitating factors include the stress and inflammation of surgery, pain, infection, hypoxaemia, hypotension, dehydration, electrolyte and glucose disturbances, urinary retention, constipation, sleep loss, and drugs such as benzodiazepines, anticholinergics and high opioid exposure; withdrawal from alcohol or sedatives can also cause it. Three motor types exist: hyperactive (agitated), hypoactive (quiet and withdrawn, the most common and most often missed) and mixed. Diagnosis is clinical and uses a validated tool such as the Confusion Assessment Method or the 4AT. Prevention with non-drug measures is the most effective approach; treatment means finding and correcting causes, and antipsychotics are kept for severe distress or danger.

Key points

• Postoperative delirium differs from emergence delirium, which is agitation on waking from anaesthesia and usually settles within minutes to hours.
• It also differs from postoperative cognitive dysfunction, a subtler decline in memory and thinking found on testing weeks to months later.
• Screening of at-risk patients before surgery (a brief cognitive test) identifies those who need preventive measures.
• Delirium is a medical emergency in the sense that it signals an underlying problem: infection, hypoxaemia, a metabolic disturbance or a drug effect.
• Physical restraints and urinary catheters worsen delirium and should be avoided when possible.

How it works

• Surgery triggers systemic inflammation, which reaches the brain and disturbs neuronal function in vulnerable patients.
• Imbalance of neurotransmitters, mainly reduced acetylcholine and excess dopamine, is thought to underlie the symptoms, which explains why anticholinergic drugs worsen delirium.
• Disrupted sleep and circadian rhythm, sensory deprivation and unfamiliar surroundings add to the brain's stress.
• The more vulnerable the brain, the smaller the insult needed: a minor infection can cause delirium in a patient with dementia.

Step by step

1. Identify at-risk patients before surgery and screen cognition — prevention works best when planned early.
2. Apply non-drug prevention: orientation, glasses and hearing aids, day-night routine, early mobilisation, fluids and nutrition — these reduce incidence.
3. Screen for delirium regularly with a validated tool such as the 4AT or the Confusion Assessment Method — hypoactive delirium is easily missed.
4. If delirium is found, treat its causes: pain, hypoxaemia, infection, retention, metabolic and drug causes — the cause, not the confusion, is the target.
5. Review and simplify the medicines — deliriogenic drugs are a common, reversible cause.
6. Use supervision, not restraints; antipsychotics only briefly, for severe distress or danger — restraints and sedatives prolong delirium.

Delirium, dementia and emergence agitation

In practice

• Assess attention in every older patient after surgery: asking for the months of the year backwards is a simple bedside test.
• Look for causes in every case: pain, hypoxaemia, infection, urinary retention, constipation, dehydration, sodium and glucose levels, drugs and withdrawal.
• Review the drug chart and stop or reduce deliriogenic drugs (benzodiazepines, anticholinergics, sedating antihistamines, high-dose opioids) when possible.
• Good pain control reduces delirium; using fewer opioids through regional techniques and non-opioids helps.
• Involve the family: familiar faces, information about the patient's usual state and help with orientation.

Next step

• Call the doctor responsible as soon as delirium is suspected: it may be the first sign of a complication.
• Ask for help from the geriatrics or psychiatry team for severe, persistent or difficult cases.
• Tell the family what delirium is and that it is usually temporary; ask for their help with orientation.
• Record the episode and its cause in the discharge summary: the patient is at higher risk in future surgery.
• Follow up cognition after discharge, because delirium can unmask or accelerate dementia.

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Elsewhere in DurgiPedia

• Mental status: orientation, attention and screening tests
• Comprehensive geriatric assessment: function, cognition, falls
• Nursing the older adult: functional assessment and geriatric syndromes
• Physical restraints: a last resort and their safe use
• Promoting sleep in hospital
• Decision-making capacity (competence) and how to assess it

Connections

← All of anaesthesia

Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: Postoperative Delirium (StatPearls (NCBI Bookshelf), 2026).

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