Delirium — an acute confusional state characterised by disturbance of consciousness, cognitive change, and fluctuating course — affects 60–80% of mechanically ventilated ICU patients and is an independent predictor of mortality, prolonged ventilation, ICU-acquired weakness, and long-term cognitive impairment. Despite this, it remains under-recognised unless actively screened for.

The CAM-ICU (Confusion Assessment Method for the ICU) is the most widely validated tool for detecting delirium in ventilated patients. It takes less than 2 minutes and requires only 10 seconds of eye opening. CAM-ICU is positive (patient is delirious) when features 1 AND 2 are present, PLUS either feature 3 OR 4: (1) acute onset or fluctuating course; (2) inattention; (3) altered level of consciousness; (4) disorganised thinking.

Prevention is more effective than treatment. Non-pharmacological strategies — reorientation, maintaining day-night cycles, early mobilisation, providing hearing aids and glasses, minimising restraints, encouraging family presence — are the most evidence-based interventions. Pharmacological treatment with haloperidol or atypical antipsychotics has very limited evidence of benefit but is used for symptom control in hyperactive delirium. Benzodiazepines should be avoided in delirium unless treating alcohol withdrawal (delirium tremens), where they are the treatment of choice.