What is the initial workup for a patient presenting with altered mental status?

Initial Workup for Altered Mental Status

The initial workup for a patient presenting with altered mental status should include vital signs, neurological examination, and first-tier laboratory tests including complete blood count, basic metabolic panel, liver function tests, and urinalysis, followed by head CT if no clear cause is identified or if specific risk factors are present. 1

Initial Assessment

Vital Signs and Physical Examination

• Measure temperature, blood pressure, heart rate, respiratory rate, and oxygen saturation
• Perform neurological examination including:
  • Level of consciousness using Glasgow Coma Scale
  • Pupillary response
  • Assessment for focal neurological deficits
  • Evaluation for meningeal signs

First-Tier Laboratory Testing

• Complete blood count (CBC)
• Basic metabolic panel (BMP)
• Liver function tests (LFTs)
• Urinalysis (high-yield test, especially in elderly patients)
• Blood cultures if febrile
• Thyroid function tests

Second-Tier Testing (Based on Clinical Suspicion)

• Toxicology screen
• Blood alcohol level
• Ammonia level (avoid routine testing in known cirrhosis)
• HIV testing
• Vitamin B12 level

Neuroimaging

• Head CT scan is indicated if:

  • No clear cause identified from laboratory tests
  • Focal neurologic deficits are present
  • History suggests trauma
  • Patient is on anticoagulants or has coagulopathy
  • Hypertensive emergency is present
  • Intracranial infection, mass, or elevated pressure is suspected

• Brain MRI (after initial stabilization) if:

  • CT is negative or inconclusive but clinical suspicion remains high
  • More detailed evaluation of brain parenchyma is needed

Electroencephalography (EEG)

• Consider continuous EEG if nonconvulsive seizures are suspected, as they may cause otherwise unexplained altered mental status 2

Common Etiologies to Consider

The most common causes of altered mental status include:

1. Neurological (34.4%) 3

   • Stroke/TIA
   • Intracranial hemorrhage
   • Seizure (including nonconvulsive status)

2. Toxicological/Pharmacological (23%) 4

   • Medication side effects or interactions
   • Alcohol intoxication or withdrawal
   • Drug overdose or withdrawal

3. Systemic/Organic (14.5%) 4

   • Organ failure
   • Hypoxia

4. Infectious (9.1%) 4

   • Urinary tract infection (especially in elderly)
   • Pneumonia
   • Sepsis
   • CNS infection

5. Metabolic/Endocrine (7.9%) 4

   • Electrolyte abnormalities
   • Hypoglycemia/hyperglycemia
   • Thyroid disorders

Common Pitfalls to Avoid

• Attributing behavioral changes to psychiatric causes without adequate medical workup
• Overreliance on neuroimaging before basic laboratory testing
• Missing atypical presentations of common infections in elderly patients
• Failure to recognize medication side effects or interactions
• Premature diagnostic closure
• Overreliance on normal neuroimaging
• Missing subtle presentations
• Inadequate documentation

Important Considerations

• Altered mental status carries a significant mortality rate (8.1% reported in one study) 4
• Elderly patients have a higher mortality rate compared to younger patients (10.8% vs. 6.9%) 4
• Most patients with unexplained altered mental status require admission for further workup and monitoring
• Consider ICU admission for patients with severe physiological derangements or those requiring close neurological monitoring

The hierarchical testing approach recommended by clinical guidelines prevents unnecessary expensive testing while ensuring that common and treatable causes are identified promptly 1. This systematic approach is essential as altered mental status represents a diverse group of conditions with potentially high morbidity and mortality if not properly identified and treated.