What is the initial workup for a patient presenting with delirium?

Initial Workup for Delirium

The initial workup for a patient presenting with delirium should include a thorough clinical assessment to identify the underlying cause, appropriate laboratory testing guided by clinical findings, and selective neuroimaging when indicated by specific clinical features. 1

Clinical Assessment

• Delirium is a medical emergency characterized by acute onset and fluctuating course of cognitive, behavioral, and/or sensorimotor symptoms; inattention; impaired level of consciousness; and disorganized thought 1
• Use validated assessment tools such as the Confusion Assessment Method (CAM) or its variants to objectively diagnose delirium 1
• Obtain a detailed history from a knowledgeable informant to determine the time course, nature, and trajectory of changes from the patient's baseline cognitive function 1
• Perform repeated assessments as cognitive status often fluctuates substantially throughout the day 1
• Identify the delirium subtype (hyperactive, hypoactive, or mixed), noting that hypoactive delirium is more common in older individuals and associated with greater morbidity and mortality 1, 2

Laboratory Investigations

• Laboratory testing should be guided by the patient's clinical evaluation rather than performed as an extensive routine battery 1
• Essential laboratory tests include:
  • Complete blood count 1, 3
  • Comprehensive metabolic panel (electrolytes, renal and liver function) 1, 3
  • Urinalysis (especially in elderly patients) 1, 3
  • Blood glucose 1, 3
  • Arterial blood gases if hypoxia is suspected 4
  • Thyroid function tests 1
  • Blood cultures if infection is suspected 3
  • Toxicology screen if substance use or medication toxicity is suspected 1, 5

Imaging Studies

• Neuroimaging should be selective rather than routine, guided by specific clinical features 1
• Head CT or MRI is indicated when there are:
  • Focal neurological deficits 1
  • History of recent head trauma 1
  • New onset seizures 1
  • Signs of increased intracranial pressure 1
  • Unexplained altered mental status despite initial workup 1

Additional Diagnostic Tests

• Electrocardiogram to assess for myocardial ischemia or arrhythmias 1, 4
• Chest radiography to evaluate for pneumonia or other pulmonary processes 1, 4
• Electroencephalography if seizure activity (including nonconvulsive status epilepticus) is suspected 1, 5
• Lumbar puncture if central nervous system infection is suspected and there are no contraindications 1, 4

Common Causes to Consider

• Infections (especially urinary tract infections and pneumonia in elderly patients) 1, 3
• Medications (particularly anticholinergics, sedatives, opioids) 1, 5
• Metabolic disturbances (electrolyte abnormalities, hypoglycemia, hypoxia) 1, 4
• Substance intoxication or withdrawal 1, 5
• Organ system failure (especially hepatic or renal) 4, 3
• Neurological conditions (stroke, hemorrhage, seizures) 1

Important Pitfalls to Avoid

• Failing to recognize hypoactive delirium, which is often missed but carries a worse prognosis 1, 2
• Attributing symptoms to dementia without investigating for acute causes 1
• Inadequate screening leading to missed diagnosis in emergency settings [1, @16@]
• Relying on routine extensive laboratory testing rather than targeted evaluation based on clinical assessment 1
• Delaying treatment of the underlying cause, which can lead to increased mortality and poorer outcomes 1, 6