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

Initial Workup for Delirium

Begin with immediate bedside glucose testing and validated delirium screening (CAM or CAM-ICU), followed by targeted laboratory investigations and selective neuroimaging based on clinical features rather than routine extensive testing. 1, 2

Immediate Assessment at Presentation

Validated Screening Tools

• Use the Confusion Assessment Method (CAM) or CAM-ICU to objectively diagnose delirium, as these tools have the best psychometric properties and prevent the common clinical failure to recognize delirium without structured assessment. 1, 3
• For ICU patients specifically, the CAM-ICU (weighted score 19.6/20) or Intensive Care Delirium Screening Checklist (ICDSC, weighted score 16.8/20) should be employed. 1
• Perform delirium screening every 8-12 hours (at least once per shift) as mental status fluctuates substantially throughout the day. 1, 3
• The two-step process includes: (1) highly sensitive delirium triage screen, followed by (2) highly specific Brief Confusion Assessment Method. 3

Critical First Action

• Obtain finger-stick blood glucose immediately upon patient contact before any other testing, as hypoglycemia is rapidly reversible, potentially fatal if missed, and frequently confused with intoxication or withdrawal. 2
• If glucose is low, administer 30-50g IV glucose urgently. 2

Detailed History from Knowledgeable Informant

• Obtain acute onset timeline and fluctuating course of symptoms. 1
• Document baseline cognitive function to distinguish delirium from underlying dementia. 3
• Review all medications, particularly vasodilators, diuretics, antipsychotics, sedative/hypnotics, and other high-risk medications. 3
• Assess for alcohol use and risk of withdrawal syndrome. 3
• Identify recent falls, loss of consciousness, or head trauma. 3

Essential Laboratory Investigations

First-Line Testing (Guided by Clinical Evaluation, Not Routine Battery)

• Complete blood count with differential to identify infection, anemia, and hematologic abnormalities. 1, 2
• Comprehensive metabolic panel including electrolytes, renal function, hepatic panel, glucose, calcium, magnesium, and phosphate. 1, 2
• Urinalysis to screen for urinary tract infections, the most common precipitating infection. 1, 2
• Thyroid-stimulating hormone (TSH) as thyroid dysfunction is a reversible cause. 1, 2
• Vitamin B12 level as deficiency causes cognitive impairment. 2

Context-Specific Additional Testing

• Toxicology screen and blood alcohol level if substance use or withdrawal is suspected. 1, 2
• Medication levels when appropriate, especially for patients on psychotropic medications. 1
• Arterial blood gas if respiratory concerns are present. 2
• Cardiac enzymes if myocardial ischemia is suspected. 2
• Coagulation studies and troponin for stroke evaluation. 2
• Pregnancy test in women of childbearing age. 2

Additional Diagnostic Tests

Electrocardiogram

• Obtain ECG to assess for myocardial ischemia or arrhythmias, particularly in geriatric patients. 1, 2

Chest Radiography

• Perform chest X-ray to evaluate for pneumonia or other pulmonary processes, as pneumonia is among the most common precipitating infections. 1, 2

Selective Neuroimaging (Not Routine)

Specific Indications for Brain CT or MRI

• Focal neurological deficits indicating potential intracranial pathology. 1, 2
• History of recent head trauma. 1, 2
• New-onset seizures. 1, 2
• Signs of increased intracranial pressure. 1, 2
• First episode of altered mental status. 1, 2
• Unexplained altered mental status despite initial workup. 1, 2
• Unsatisfactory response to treatment of precipitating factors. 2

When NOT to Image

• Do not obtain routine brain imaging for recurrent, non-focal presentations similar to prior episodes. 2
• MRI is preferred when available, though challenges exist with combative patients unable to follow commands. 1

Common Underlying Causes to Systematically Evaluate

Infections (Most Common)

• Urinary tract infection and pneumonia are the most frequent precipitating infections. 3, 1

Medications

• Review all current medications with special attention to recent additions or dose changes. 1
• Consider anticholinergic burden and polypharmacy effects. 3

Metabolic Disturbances

• Electrolyte imbalances, renal dysfunction, hepatic dysfunction, hypo/hyperglycemia. 1, 2

Substance Intoxication or Withdrawal

• Alcohol withdrawal is a critical consideration requiring specific management. 3, 1

Neurological Conditions

• Stroke, seizures, increased intracranial pressure. 1

Critical Pitfalls to Avoid

Hypoactive Delirium

• Failing to recognize hypoactive delirium is the most common missed diagnosis, as it lacks the obvious agitation of hyperactive delirium and is frequently mistaken for depression or fatigue. 1
• Hypoactive delirium is the most frequent clinical subtype in cancer patients and commonly missed by clinical teams. 1

Attributing to Dementia

• Never attribute acute symptoms to pre-existing dementia without investigating for acute reversible causes. 1
• Delirium commonly occurs superimposed on dementia, and the acute component requires urgent evaluation. 3

Assuming Intoxication

• Never assume intoxication without first ruling out hypoglycemia, as clinical presentations overlap significantly and hypoglycemia causes permanent brain damage. 2

Inadequate Screening

• Without validated screening tools, bedside nurses and physicians fail to recognize delirium in the majority of cases. 3

Delaying Glucose Testing

• Do not delay glucose testing to obtain neuroimaging first. 2

Over-Testing

• Avoid reflexive extensive laboratory panels, as history and physical examination predict 83-98% of clinically significant abnormalities. 2
• Routine testing yields only 1.4-1.8% clinically meaningful results not detected by history and physical examination. 2

Special Populations Requiring Enhanced Vigilance

High-Risk Groups

• Patients aged ≥65 years. 2
• Pre-existing dementia (strongest baseline risk factor). 1
• History of hypertension or alcoholism. 1
• High severity of illness at admission. 1
• Cancer patients, particularly those with advanced disease (up to 88% develop delirium in final weeks). 1
• ICU patients on mechanical ventilation or receiving parenteral sedatives/opioids. 1
• Patients with severe sepsis/shock. 1