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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Delirium = acute onset, fluctuating course, impaired attention/awareness, cognitive disturbance, and medical/substance cause
- Inattention distinguishes delirium from dementia, depression, and primary psychosis
- Common causes: infection, hypoxia, metabolic derangement, medications, pain, urinary retention, constipation, intoxication, withdrawal
- First-line is treating the cause plus reorientation, sleep, mobility, hydration, and sensory aids
- Antipsychotics are only for dangerous agitation; benzodiazepines worsen most delirium except alcohol/benzodiazepine withdrawal
Overview
Delirium is an acute neuropsychiatric syndrome caused by physiologic disturbance. It may be hyperactive, hypoactive, or mixed. Hypoactive delirium is often missed and mistaken for depression or fatigue.
Epidemiology
Delirium is common in hospitalized older adults, ICU and postoperative patients, and those with dementia. Risks include advanced age, baseline cognitive impairment, sensory impairment, polypharmacy, dehydration, sleep deprivation, infection, anticholinergics, sedatives, opioids, and restraints.
Clinical Features
Symptoms
Acute confusion with fluctuating alertness, worse at night
Inattention: cannot recite months backward, distractible
Disorganized thinking, altered sleep-wake cycle
Visual hallucinations, illusions, agitation, or paranoia
Hypoactive withdrawal, somnolence, reduced speech, poor intake
Signs
Altered level of consciousness
Abnormal vitals, hypoxia, fever, dehydration, pain, urinary retention
Tremor/diaphoresis/autonomic instability suggests withdrawal
Focal neurological signs suggest stroke/seizure/CNS infection
Investigations
First-line
CAMAcute/fluctuating course + inattention + disorganized thinking or altered consciousness
Basic evaluationVitals, oxygen, glucose, CBC, CMP, UA when symptomatic, medication review, pain, bowel/bladder
Targeted testingECG/troponin, CXR, cultures, TSH, B12, ammonia, toxicology, alcohol/drug levels as indicated
Second-line
NeuroimagingHead trauma, focal deficits, anticoagulation, seizures, papilledema, severe headache, persistent unexplained delirium
EEGConcern for nonconvulsive status epilepticus
LPMeningitis/encephalitis suspected
Specialist
Geriatrics/psychiatry/neurologySevere agitation, diagnostic uncertainty, catatonia, or persistent delirium
ICUSevere withdrawal, shock, hypoxia, sepsis, airway/close monitoring
1
Treat underlying cause
- Correct hypoxia, infection, dehydration, electrolytes, hypoglycemia, pain, urinary retention, constipation, sleep deprivation
- Stop/reduce deliriogenic medications: anticholinergics, benzodiazepines, sedatives, opioids when possible, steroids, H2 blockers
- Treat alcohol/benzodiazepine withdrawal with benzodiazepines
2
Nonpharmacologic bundle
- Reorientation, clocks/calendars, family presence, glasses/hearing aids, mobilization, hydration/nutrition, sleep protection
- Avoid restraints and urinary catheters when possible
- Provide pain control without oversedation
3
Medication only if dangerous
- Low-dose haloperidol or atypical antipsychotic only if danger or essential care cannot be delivered
- Check QTc, Parkinson/Lewy body dementia risk, EPS risk, and NMS history
- Use lowest dose shortest duration
Complications
- Falls/injury:
- Aspiration and malnutrition:
- Prolonged hospitalization and mortality:
- Long-term cognitive decline:
- Missed sepsis, hypoxia, withdrawal, or stroke:
USMLE Step 2 CK Exam Tips
- 1Acute fluctuating inattention = delirium
- 2Hypoactive delirium is common and missed
- 3Benzodiazepines worsen delirium except alcohol/benzo withdrawal
- 4Visual hallucinations are more typical of delirium than schizophrenia
- 5Best next step is find and treat medical cause
- 6Antipsychotics treat dangerous agitation, not delirium itself
practicetest your knowledge on deliriumApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — psychiatry and beyond.
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