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

Initial Workup for Altered Mental Status

The initial workup for altered mental status should include assessment of vital signs, neurological examination, metabolic laboratory assessment, and head CT without contrast when indicated by focal neurological deficits or first episode presentation. 1

Initial Assessment and Stabilization

• Airway protection is the first priority in patients with altered mental status to prevent aspiration, with transfer to a monitored setting if necessary 2
• Assess mental status severity using validated scales such as the Glasgow Coma Scale or West Haven criteria to objectively quantify impairment 1, 2
• Document vital signs, as abnormalities may indicate specific etiologies (fever suggesting infection, hypotension suggesting shock) 1
• Evaluate for focal neurological deficits, which significantly increase the likelihood of intracranial pathology requiring immediate neuroimaging 1

Laboratory Investigations

• Obtain comprehensive metabolic laboratory assessment including: 1, 2
  • Complete blood count
  • Comprehensive metabolic panel (electrolytes, renal function, liver function)
  • Blood glucose
  • Urinalysis
• Toxicology screens should be performed when substance use is suspected 1
• History and physical examination have 94% sensitivity for identifying medical conditions, while laboratory studies alone have only 20% sensitivity 1
• Most abnormal laboratory results can be predicted from a careful history and physical examination 1

Neuroimaging

• Head CT without contrast is usually appropriate as first-line neuroimaging for patients with: 1, 2
  • First episode of altered mental status
  • Focal neurological deficits
  • Seizures
  • New focal neurological signs
  • Increased risk for intracranial bleeding
• The yield of acute contributory findings on CT ranges from 2% to 45% based on trial design and inclusion criteria 1
• Brain MRI may be appropriate when CT is negative but clinical suspicion for intracranial pathology remains high 1, 2

Common Etiologies to Consider

• Neurological causes (30-35%): intracranial mass, encephalitis, meningitis 1
• Toxicologic/Pharmacologic causes (20-25%): medication side effects, alcohol intoxication, illicit drug use 1
• Metabolic/Systemic causes (15-20%): hypoglycemia, hyperglycemia, electrolyte abnormalities, hepatic encephalopathy, uremia 1
• Infectious causes (9-18%): sepsis, urinary tract infection, pneumonia, meningitis 1

Special Considerations

• In elderly patients, delirium is often multifactorial and carries higher mortality 1, 2
• In patients with cirrhosis, hepatic encephalopathy is a common cause of altered mental status but remains a diagnosis of exclusion 1, 2
• For patients with known intracranial pathology and worsening mental status, neuroimaging should be performed to assess for progression 1
• Medication side effects, including from drugs like pregabalin (Lyrica), can cause altered mental status and should be considered 3

Pitfalls to Avoid

• Attributing altered mental status solely to psychiatric causes without adequate medical workup 4, 1, 2
• Failing to consider multiple concurrent etiologies, especially in elderly patients 1, 2
• Relying on ammonia levels alone to diagnose hepatic encephalopathy in cirrhotic patients 1, 2
• Delaying empiric treatment while awaiting diagnostic results in potentially life-threatening conditions 1, 2
• Extensive, routine laboratory testing without clinical indication can lead to false positive results that are 8 times more frequent than true positives 4