Hypoactive Delirium

Hypoactive delirium is an acute disturbance of attention and awareness with reduced psychomotor activity, so that the patient is lethargic, quiet and withdrawn rather than agitated. It is the commonest motor subtype in older people and is often overlooked or mistaken for depression, fatigue or dementia.

It accounts for a large share of delirium in hospital, and it carries a worse prognosis than the hyperactive form because it is detected late.

Pathophysiology. Delirium reflects acute network failure in vulnerable brains from neurotransmitter imbalance (acetylcholine deficiency, dopamine excess), inflammation, impaired metabolism and stress hormones. Predisposing factors are age, dementia, frailty, sensory impairment and multimorbidity. Precipitants include infection, drugs, surgery, dehydration, hypoxia, pain and urinary retention.

Drowsiness, reduced speech, slowed movement, poor oral intake, inattention, apathy and fluctuating course. Patients may be calm and appear "no trouble". Complications include pressure injury, aspiration, falls, dehydration and delayed recovery.

Screen every older admission with a validated tool for attention and arousal, and repeat daily. Test attention by months of the year backwards. Find the cause with a full history of drugs and a medication review, observations, glucose, full blood count, urea and electrolytes, calcium, liver tests, C-reactive protein, urinalysis if symptomatic, ECG and chest radiograph. Check for retention and constipation. Image the brain after a fall, with focal signs or on anticoagulation. Consider EEG for non-convulsive status.

Differential diagnosis.

• Depression and dementia.
• Non-convulsive status epilepticus, stroke and subdural haematoma.
• Hypothyroidism, Wernicke encephalopathy and hepatic encephalopathy.
• Opioid or sedative toxicity.

Find and treat the cause. Provide non-drug care: reorientation, glasses and hearing aids, mobility, sleep protection, hydration, nutrition, bowel and bladder care, and family presence. Avoid sedatives, as they worsen hypoactive delirium; antipsychotics have no proven benefit. Give thiamine 100 mg daily if alcohol use or malnutrition is suspected.

Monitoring. Repeat attention testing at least daily, with fluid balance and weight.