Learning Objective
Recognize the clinical features of delirium, differentiate it from other causes of altered mental status, understand common etiologies, and outline evidence-based management strategies.
Definition
Delirium is an acute, reversible disturbance in attention and cognition with “waxing and waning” levels of consciousness.
Key Clinical Features
| Feature | Description | Notes |
|---|---|---|
| Onset | Acute | Hours to days |
| Attention | ↓ attention span | Key distinguishing feature |
| Consciousness | Fluctuating (“waxing and waning”) | May appear drowsy or agitated |
| Thinking | Disorganized | Often incoherent speech or illogical thoughts |
| Perception | Hallucinations (commonly visual), illusions | Misinterpretations of the environment |
| Sleep | Disturbance in the sleep-wake cycle | Daytime sleepiness, nighttime agitation |
| Cognition | Memory deficits, confusion | Short-term memory is often affected |
| Behavior | Agitation or psychomotor retardation | Often fluctuates during the day |
| EEG | Diffuse slowing | Non-specific, supportive |
Etiology
1. Medical Conditions
- CNS disease (stroke, hemorrhage, infection)
- Metabolic/electrolyte disturbances
- Infection (UTI, pneumonia, sepsis)
- Trauma
- Urinary/fecal retention
2. Medications
- Anticholinergics
- Benzodiazepines (especially in the elderly)
- Opioids
3. Substances
- Withdrawal from alcohol or sedatives
- Intoxication
Epidemiology
- The most common cause of altered mental status in inpatient settings
- Frequently seen in ICU patients or during prolonged hospitalizations
- Higher prevalence in older adults
Pathophysiology
- Changes in sensorium due to acute disruption of brain homeostasis
- EEG: diffuse slowing of the background rhythm
Management
| Approach | Details |
|---|---|
| Treat the underlying cause | Infection, metabolic imbalance, medication-induced delirium |
| Symptom management | Orientation protocols (clock/calendar), sleep hygiene, cognitive stimulation |
| Pharmacologic | Antipsychotics (e.g., haloperidol) if severe agitation |
| Avoid | Unnecessary restraints, medications worsening delirium (anticholinergics, benzodiazepines, opioids) |
Key Points for USMLE Step 1
- Delirium is acute and reversible, unlike dementia (chronic, progressive).
- Hallucinations are usually visual, whereas in psychiatric disorders, auditory hallucinations predominate.
- Fluctuating attention is the hallmark.
- EEG may show diffuse slowing, supportive but non-diagnostic.
- Identify the underlying cause first; medications and supportive care are adjuncts.
