Delirium in the ICU: screening and prevention

Concept

Many very sick ICU patients become confused for days; regular checks find it early and simple measures like sleep, movement and less sedation help prevent it.

Updated Nov 13, 2026

What it is

Delirium is an acute brain dysfunction with a fluctuating course, inattention and either disorganised thinking or an altered level of consciousness. It is very common in the intensive care unit, especially in mechanically ventilated patients, and is linked to longer ventilation and stay, higher mortality and long-term cognitive impairment, part of the post-intensive care syndrome. Most ICU delirium is hypoactive (quiet, withdrawn, drowsy), which is easily missed without screening; hyperactive and mixed forms are more obvious. Predisposing factors include older age, pre-existing cognitive impairment, alcohol use and severity of illness; precipitating factors include benzodiazepines and deep sedation, sepsis, hypoxaemia, metabolic disturbance, sleep disruption, immobility and restraints. Screening with a validated tool, such as the Confusion Assessment Method for the ICU (CAM-ICU) or the Intensive Care Delirium Screening Checklist (ICDSC), is done at least once per shift. Prevention rests on the ABCDEF bundle; treatment means finding and fixing the cause, with drugs only for distressing or dangerous agitation.

Key points

Delirium in the ICU independently predicts mortality, longer ventilation and long-term cognitive decline.
Benzodiazepines are a leading modifiable precipitant; alcohol or benzodiazepine withdrawal is the exception where they are the treatment.
Dexmedetomidine may be preferred to benzodiazepines for sedation and can help agitated delirium that prevents extubation.
Physical restraints increase agitation and injury and are a risk factor for delirium; they are a last resort.
Anticholinergic drugs, sleep deprivation, untreated pain, urinary retention and constipation are common, reversible contributors.

How it works

Inflammation, impaired brain perfusion and oxygen delivery, and imbalance of neurotransmitters (too little acetylcholine, too much dopamine) are thought to disrupt attention networks.
GABA-ergic sedatives disturb normal sleep architecture and arousal, which may explain their link with delirium.
Loss of day-night cues, noise, light and immobility disrupt the circadian rhythm.

Step by step

Check the sedation level first with RASS — delirium can be assessed only if the patient responds to voice.
Screen with CAM-ICU or ICDSC at least once per shift and after changes — hypoactive delirium is otherwise missed.
If positive, search for the cause: infection, hypoxaemia, metabolic upset, drugs, withdrawal, pain and retention — treating the cause is the treatment.
Review drugs and stop or replace benzodiazepines and anticholinergics where possible — they precipitate delirium.
Protect sleep: lights and noise down at night, daylight and activity by day — this restores the circadian rhythm.
Mobilise early and reorient often, with glasses, hearing aids and family — these lower the incidence of delirium.
Use antipsychotics or dexmedetomidine only for distressing or dangerous agitation, briefly — they do not cure delirium.

CAM-ICU: four features

Feature	What it means	How it is tested
1. Acute change or fluctuation	Mental status differs from baseline or varies over the day	Compare with baseline and recent RASS or GCS
2. Inattention	Cannot focus attention	Squeeze the hand on a target letter in a spoken sequence
3. Altered level of consciousness	Any RASS other than alert and calm	Current RASS
4. Disorganised thinking	Illogical or confused thoughts	Simple yes-no questions and a command

In practice

A new delirium is a warning sign: look for sepsis, hypoxaemia, hypoglycaemia, electrolyte disorders, drug effects and withdrawal.
Do not label a quiet, drowsy patient as 'settled' without screening; hypoactive delirium is often missed.
Agitated patients who pull at tubes need a safe bedside plan: treat the cause, use calm reorientation and family presence, and use drugs or restraints only briefly.
Survivors and families benefit from follow-up for memory, mood and function after ICU discharge.

Next step

Report a new positive screen to the senior and start a structured search for the cause the same shift.
Call a senior urgently for agitation that endangers the patient or staff, or for delirium with a falling level of consciousness.
Record screening results each shift so trends are visible to the whole team.
Stop antipsychotics once the delirium resolves and do not continue them at ICU discharge without a reason.
Arrange post-ICU follow-up for cognition, mood and function, and tell the family what to expect.

Test yourself

Think of the answer, then tap the question to see it.

What makes the CAM-ICU positive?

An acute change or fluctuating course of mental status and inattention, plus either an altered level of consciousness or disorganised thinking.

Which type of ICU delirium is most common, and why does it matter?

Hypoactive delirium; it looks like calm drowsiness, is easily missed without screening and carries a poor prognosis.

Why are benzodiazepines avoided for routine ICU sedation?

They are associated with more delirium and longer ventilation; they remain the treatment for alcohol or benzodiazepine withdrawal.

What sedation level is needed before screening for delirium?

The patient must respond to voice (RASS −3 or lighter); if only physical stimulation or nothing produces a response, the patient is in coma and cannot be assessed.

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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: ICU Delirium (StatPearls (NCBI Bookshelf), 2024).

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