Delirium is a state of acute confusional change, marked by reduced attention, fluctuating consciousness, disorganized thinking, and impaired cognition. It is a medical emergency because it often signals an underlying serious illness or systemic disturbance.
Delirium is especially common in elderly patients, ICU patients, and those with multiple comorbidities, but it can occur in any age group. Identifying the root cause is crucial because delirium is potentially reversible if treated early.
To simplify the wide range of possible causes, clinicians use the mnemonic DELIRIUM, which covers the major etiological categories.
The DELIRIUM Mnemonic
- D – Drugs
- E – Epilepsy / Electrolyte imbalance
- L – Liver failure / Low oxygen (MI, PE)
- I – Infection
- R – Retention (urinary/fecal)
- I – Intracranial causes
- U – Uremia
- M – Metabolism disturbances
Detailed Explanation of Each Cause
1. Drugs
Medications are among the most common contributors to delirium.
- Causative agents: sedatives, anticholinergics, opioids, antihistamines, corticosteroids, and polypharmacy.
- Mechanism: These drugs may interfere with neurotransmitters like acetylcholine, leading to confusion.
- Example: Post-operative delirium due to excessive opioid analgesia.
2. Epilepsy / Electrolyte Imbalance
- Postictal confusion after a seizure is a well-known cause of delirium.
- Electrolyte imbalances such as hyponatremia, hypercalcemia, or hypomagnesemia can impair neuronal activity.
- Example: Severe hyponatremia leading to confusion, seizures, and coma.
3. Liver Failure / Low Oxygen (MI, PE)
- Hepatic encephalopathy occurs in liver failure when ammonia and other toxins accumulate, impairing brain function.
- Low oxygen levels from conditions like myocardial infarction (MI) or pulmonary embolism (PE) reduce cerebral perfusion, triggering delirium.
- Example: A cirrhotic patient with GI bleed developing confusion due to hepatic encephalopathy.
4. Infection
Infections, particularly in the elderly, often present with delirium instead of typical fever or raised WBC count.
- Common infections: urinary tract infection (UTI), pneumonia, sepsis, meningitis, encephalitis.
- Mechanism: systemic inflammation, cytokine release, and sepsis-related encephalopathy.
- Example: An elderly woman presenting with acute delirium due to undiagnosed UTI.
5. Retention (Urinary / Fecal)
Retention syndromes are underrecognized but significant causes of confusion.
- Urinary retention: especially in patients with BPH, post-surgery, or catheter blockage.
- Fecal impaction: can cause severe discomfort and lead to agitation and delirium.
- Example: A confused ICU patient suddenly settling after catheterization of a distended bladder.
6. Intracranial Causes
Neurological insults can directly impair consciousness and cognition.
- Stroke, hemorrhage, subdural hematoma, brain tumor, meningitis, encephalitis.
- Example: Acute onset confusion in a hypertensive patient due to intracerebral bleed.
7. Uremia
Renal failure results in accumulation of nitrogenous waste products (uremia), which disrupt brain function.
- Symptoms: confusion, agitation, tremors, seizures, coma.
- Diagnosis: elevated urea/creatinine.
- Treatment: dialysis is often necessary.
8. Metabolism Disturbances
Endocrine and metabolic disorders are frequent contributors to delirium.
- Hypoglycemia, hyperglycemia, thyroid disorders, Addison’s disease, Cushing’s syndrome, vitamin deficiencies (B1, B12).
- Example: Hypoglycemia in a diabetic patient leading to acute confusion.
Clinical Relevance of the DELIRIUM Mnemonic
The DELIRIUM mnemonic ensures that clinicians perform a systematic search for reversible causes of delirium. Since delirium is multifactorial, often more than one cause is involved, especially in elderly or ICU patients.
By checking each DELIRIUM category, clinicians can quickly rule in or rule out possible triggers, ensuring timely intervention.
Diagnostic Approach to Delirium
- History & Clinical Examination – recent illness, drug history, comorbidities.
- Bedside tests – vitals, glucose, oxygen saturation, neurological exam.
- Laboratory investigations – electrolytes, renal/liver function, CBC, infection markers.
- Imaging – CT/MRI brain if intracranial causes suspected.
- Special tests – EEG for seizures, cultures for infection, ammonia for liver disease.
Quick Reference Table – DELIRIUM Mnemonic
| Letter | Cause | Examples |
|---|---|---|
| D | Drugs | Sedatives, anticholinergics, opioids |
| E | Epilepsy / Electrolyte imbalance | Seizures, hyponatremia, hypercalcemia |
| L | Liver failure / Low oxygen | Hepatic encephalopathy, MI, PE |
| I | Infection | UTI, pneumonia, meningitis, sepsis |
| R | Retention | Urinary retention, fecal impaction |
| I | Intracranial causes | Stroke, bleed, tumor, meningitis |
| U | Uremia | Acute/chronic renal failure |
| M | Metabolism disturbances | Hypoglycemia, thyroid disorders |
Frequently Asked Questions (FAQ)
1. What is delirium?
Delirium is an acute confusional state characterized by fluctuating consciousness, inattention, and disorganized thinking.
2. How does delirium differ from dementia?
Delirium is acute, fluctuating, and reversible, while dementia is chronic, progressive, and irreversible.
3. What are the common triggers of delirium in hospitalized patients?
Drugs, infections, electrolyte imbalances, metabolic disturbances, and hypoxia.
4. Can delirium be prevented?
Yes. Prevention strategies include avoiding unnecessary medications, ensuring hydration and nutrition, treating infections early, and maintaining sleep-wake cycles in ICU.
5. What is the most important step in treating delirium?
Identifying and treating the underlying cause. Supportive care with reorientation, safety, and sometimes low-dose antipsychotics may be needed.
6. Who is at highest risk of delirium?
Elderly patients, ICU patients, those with multiple comorbidities, and post-surgical patients.
