Why is your patient suddenly confused after surgery?

The question

Your patient knew everyone this morning and is suddenly muddled tonight: is it just her age, why has it happened, and what do I do?

Understand

Your patient knew every nurse's name this morning. Tonight she's looking for her shoes. It could be delirium: a sudden change in thinking and attention that comes and goes and can worsen at night. It isn't just old age, and a quiet, sleepy patient can have it too. A student reports the change to the supervising nurse, so the team can look for the cause.

1. Delirium is a sudden change in thinking and attention. It comes on in hours or days, comes and goes, and can worsen in the evening or night.
2. It is thought to build from a vulnerable brain plus stressors such as surgery, pain, infection, some medicines and lack of sleep. In an older person, one or two can be enough.

Key takeaways

• Delirium comes on over hours to a few days, and symptoms fluctuate through the day.
• An acute change in behaviour or thinking in hospital should be promptly assessed with a validated tool by a clinician trained to assess delirium.
• It can be the only sign that a patient is deteriorating. Victoria's Department of Health says to treat it as a medical emergency.
• All team members can raise concerns. A student tells the supervising nurse; follow your local policy.

In practice

• Stay with the patient and tell your supervising nurse what changed, and when.
• A quiet, drowsy change counts too. Family can say what's normal for them.

Check yourself

A patient who chatted all morning is now drowsy and staring. What now?

Words to know

Delirium

a sudden change in thinking and attention that comes and goes

Hypoactive delirium

the quiet type: drowsy, withdrawn, often missed (hypo- (low) + active)

Transcript

Sources

1. ACSQHC, Delirium Clinical Care Standard 2021: definition, hours to days, fluctuation, confused with dementia, greater risk after surgery in older people, hypoactive delirium often missed, falls and longer stay, 4AT, family as best source (read 4 November 2026)
2. ACSQHC, Delirium Clinical Care Standard, fact sheet for clinicians: an acute change is promptly assessed with a validated tool by a trained clinician; family asked about recent changes (read 4 November 2026)
3. ACSQHC, Delirium Clinical Care Standard, guide for consumers: symptoms fluctuate and may worsen in the evening or night; a medical check for the cause; family alert a clinician (read 4 November 2026)
4. healthdirect, Delirium: sudden change in thinking or behaviour; dementia worsens slowly; higher chance after surgery; a cause isn't always found (read 5 November 2026)
5. Healthify NZ, Delirium: causes including infections, medicines, surgery, lack of sleep, unrelieved pain; don't assume confusion is long-term dementia (read 5 November 2026)
6. Victorian Department of Health, Identifying delirium: screening and assessment: often worse at night; all team members escalate; treat as a medical emergency; hypoactive delirium (read 5 November 2026)
7. Korean Journal of Anesthesiology 2019, Postoperative delirium (open-access review): poorly understood; inflammation and neurochemical imbalance as leading hypotheses; predisposing plus precipitating factors (read 4 November 2026)
8. The 4AT, user guide: a four-item delirium test (read 4 November 2026)

Checked against these sources at the time of publishing. Sources change, so check the date above and your local policy. Spotted an error? Tell us and we'll correct it.