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 systematic approach focusing on potentially life-threatening reversible causes, with complete blood count, basic metabolic panel, liver function tests, urinalysis, and brain imaging when indicated by clinical findings. 1

Primary Assessment

1. Vital Signs and Stabilization

   • Assess ABCs (Airway, Breathing, Circulation)
   • Measure temperature, blood pressure, heart rate, respiratory rate, and oxygen saturation
   • Check blood glucose immediately (point-of-care testing)
   • Assess neurological status using Glasgow Coma Scale

2. Focused History (from family, EMS, or medical records)

   • Onset and progression of symptoms
   • Recent medications or substance use
   • Medical history, especially neurological conditions
   • Recent trauma, infections, or behavioral changes

3. Targeted Physical Examination

   • Complete neurological examination including pupillary response and focal deficits
   • Signs of trauma, especially head injury
   • Signs of infection (meningeal signs, fever)
   • Evidence of toxidromes or withdrawal syndromes

Laboratory Evaluation

1. First-line Laboratory Tests

   • Complete blood count (CBC)
   • Basic metabolic panel (BMP)
   • Liver function tests (LFTs)
   • Urinalysis
   • Blood cultures if febrile 1

2. Additional Laboratory Tests (based on clinical suspicion)

   • Thyroid function tests (TSH)
   • Vitamin B12 level (especially in elderly or malnourished patients)
   • Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
   • Toxicology screen
   • Arterial blood gas analysis
   • Ammonia level (if liver disease suspected)

Important Note: Urinalysis is particularly high-yield in elderly patients, as UTIs are among the most common causes of delirium in this population 1

Imaging Studies

1. Brain Imaging

   • Brain CT or MRI is indicated when:
     • No clear cause is identified from laboratory tests
     • Focal neurologic deficits are present
     • History of trauma exists
     • Clinical suspicion for intracranial pathology remains high 1

2. Additional Imaging (based on clinical suspicion)

   • Chest X-ray (to evaluate for pneumonia or other pulmonary causes)
   • Abdominal imaging (if intra-abdominal pathology suspected)

Special Considerations

1. Electroencephalography (EEG)

   • Consider when nonconvulsive status epilepticus is suspected
   • Particularly important in unexplained altered mental status 2

2. Lumbar Puncture

   • Consider when meningitis or encephalitis is suspected
   • Especially important if fever, headache, or meningeal signs are present

Common Etiologies to Consider

The most frequently encountered diagnostic categories causing altered mental status are:

• Neurological disorders (35.0%)
• Pharmacological and toxicological causes (23.0%)
• Systemic and organic disorders (14.5%)
• Infectious causes (9.1%)
• Endocrine/metabolic abnormalities (7.9%) 3

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 1
• Premature diagnostic closure
• Missing subtle presentations of serious conditions

Management Approach

1. Treat identified underlying causes

   • Antibiotics for infections
   • Correction of electrolyte abnormalities
   • Antidotes for toxins
   • Anticonvulsants for seizures 1

2. Supportive care

   • Maintain normothermia
   • Ensure adequate oxygenation and perfusion
   • Avoid physical restraints when possible
   • Provide reorientation strategies 1

Most patients with unexplained altered mental status require admission for further workup and monitoring, with consideration of ICU admission for patients with severe physiological derangements or those requiring close neurological monitoring 1.

Early diagnosis accuracy is moderately good (correlation r²=0.807), but physicians should maintain a broad differential diagnosis as the presentation can be complex 4.