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 with altered mental status should include a thorough clinical assessment, basic laboratory tests, and selective neuroimaging based on risk factors, with CT head being usually appropriate for patients with suspected intracranial pathology or focal neurologic deficits 1.

Clinical Assessment

History

• Obtain history from patient, family, or witnesses regarding:
  • Onset and duration of symptoms
  • Recent trauma, falls, or head injury
  • Current medications and recent changes
  • Substance use (alcohol, illicit drugs)
  • Medical conditions (diabetes, liver disease, kidney disease)
  • Prior episodes of altered mental status
  • Recent infections or fevers

Physical Examination

• Vital signs (temperature, blood pressure, heart rate, respiratory rate, oxygen saturation)
• Neurological examination:
  • Level of consciousness (using Glasgow Coma Scale)
  • Pupillary response
  • Focal neurological deficits
  • Meningeal signs
• Signs of trauma
• Skin examination (rashes, jaundice)
• Cardiopulmonary examination
• Abdominal examination

Laboratory Testing

First-line Laboratory Tests

• Complete blood count
• Basic metabolic panel (electrolytes, BUN, creatinine, glucose)
• Liver function tests
• Urinalysis
• Toxicology screen (urine and/or blood)
• Blood alcohol level
• Arterial blood gas (if respiratory distress)

Second-line Laboratory Tests (Based on Clinical Suspicion)

• Thyroid function tests
• Ammonia level (if liver disease suspected)
• Blood cultures (if infection suspected)
• HIV testing (if risk factors present)
• Vitamin B12 level (if deficiency suspected)

Imaging Studies

Neuroimaging

• Head CT without contrast: Usually appropriate for patients with suspected intracranial pathology or focal neurologic deficits 1

  • Indications:
    • First episode of altered mental status
    • Presence of focal neurological deficits
    • History of trauma
    • Seizures
    • Severe headache
    • Anticoagulant use
    • Immunocompromised state

• Brain MRI: May be appropriate after initial stabilization if CT is negative or inconclusive but clinical suspicion remains high 1

  • Superior for detecting:
    • Small ischemic infarcts
    • Subtle cases of subarachnoid hemorrhage
    • Encephalitis
    • Focal cerebral edema

Other Imaging

• Chest X-ray (if respiratory symptoms or suspected pneumonia)
• Abdominal imaging (if abdominal pathology suspected)

Additional Diagnostic Tests

Based on Clinical Suspicion

• Electrocardiogram (if cardiac etiology suspected)
• Lumbar puncture (if meningitis/encephalitis suspected and no contraindications)
• Electroencephalogram (if seizure activity or nonconvulsive status epilepticus suspected)

Special Considerations

Hepatic Encephalopathy

For patients with known cirrhosis and altered mental status:

• Investigate precipitating factors (infections, GI bleeding, electrolyte disorders, kidney injury) 1
• Consider empiric lactulose treatment while workup is ongoing 1
• Avoid routine ammonia testing as levels are variable and may be elevated in non-hepatic encephalopathy conditions 1

Elderly Patients

• Higher risk of delirium and mortality 2, 3
• More likely to have multiple contributing factors
• Consider broader initial testing including thyroid function, vitamin B12 levels, and urinalysis 1

Common Pitfalls to Avoid

1. Premature diagnostic closure: Assuming a psychiatric cause without adequate medical workup
2. Overreliance on normal neuroimaging: A normal CT does not rule out all neurological causes
3. Missing subtle presentations: Delirium can present with subtle disturbances in consciousness
4. Inadequate documentation: Failure to document mental status changes and neurological examination
5. Excessive laboratory testing: Routine extensive laboratory testing has low yield without clinical indication 1

Etiologic Categories to Consider

Based on research, the most common causes of altered mental status include 2, 3:

1. Neurological (30-35%)
2. Toxicological/pharmacological (20-23%)
3. Systemic/organic (14-15%)
4. Infectious (9-18%)
5. Metabolic/endocrine (8-12%)
6. Psychiatric (4%)
7. Traumatic (2%)

Remember that altered mental status has a high mortality rate (8-11%) and requires prompt evaluation and treatment to decrease morbidity and mortality 2, 3.