• Altered mental status is common, representing 5-10% of all patient visits to the emergency department (ED).
  • Amongst vulnerable populations (elderly, demented) these rates are even higher.
  • When undiagnosed, delirium results in significantly increased mortality rates. 
• Delirium is defined by the DSM-5 as an acute, fluctuating change in attention, awareness, and cognition.
• Given the broad differential, it is important to have a concise, evidence-based approach to investigating and diagnosing this common chief complaint.

• While many scoring tools exist to help diagnose delirium (CAM, RASS), the ED environment (loud noises, distractions) and time constraints make delirium a clinical diagnosis. As such, a thorough history from the patient and collateral sources (if possible) is of the highest utility. 
  • Include a medication review to assess for possible etiologies.
• All patients with altered level of consciousness should receive an initial assessment of vital signs and ABC’s for stability, and a complete physical exam, including a thorough neuro exam.
• A basic workup should include a complete blood count, basic electrolytes panel (sodium, potassium, chloride, bicarbonate, blood urea nitrogen, and creatinine), liver function tests, urinalysis, toxicology panel (EtOH, acetaminophen, salicylates), VBG, and ECG. 
• Further investigations should be targeted based on the clinical presentation, in order to narrow down the differential diagnosis.
  • Drugs: Urine drug screen, serum osmolality.
  • Infection: blood cultures, chest XR, urine culture, line culture, LP.
  • Metabolic: extended electrolytes (calcium, magnesium, phosphate), thyroid function.
  • Structural: head CT.

Pitfalls

• Given the broad differential diagnosis for altered mental status, many clinicians opt for a broad approach to investigative testing. Significant caution should be used with certain investigations.
• CT brain scan should not be used routinely but should be considered in patients with the following indications: (SIGN, 4)
  • New focal neurological signs
  • Reduced level of consciousness not adequately explained by another cause
  • History of recent falls
  • Head injury
  • Anticoagulation therapy.
• Lumbar puncture should not be performed routinely in patients presenting with delirium.
• Results of urinalysis should be interpreted cautiously. Asymptomatic bacteriuria is common. and delirium should not be attributed to a UTI without accompanying clinical signs and symptoms. 

Differential Diagnosis

• A simple approach to altered mental status utilizes the DIMS mnemonic:
  • Drugs (withdrawal or overdose)
    • Medications: benzodiazepines, sleeping medications, anticholinergics, neuroleptics, psychotropics
    • Drugs of abuse: Alcohol, narcotics
  • Infection: pneumonia, UTI, sepsis, cellulitis, endocarditis, meningitis
  • Metabolic: hypo/hyperglycemia, hyponatremia, hypo/hyperkalemia, hypo/hypercalcemia, AKI/renal failure, uremia, hypoxia, hypercarbia, acid/base disorders, hyper/hypothyroidism, Wernicke’s encephalopathy
  • Structural:
    • Cardiac: Myocardial infarction, arrhythmia, heart failure
    • Hepatic encephalopathy
    • Neurologic: intracranial hemorrhage, ischemic stroke, subacute mass.
  • Other: seizures, psychiatric diagnoses (should be a diagnosis of exclusion).

1. Episode 13, Part 1: Killer Coma Cases – The Found Down Patient. From emergencymedicinecases.com.

   
   

1. Smith AT, Han JH. Altered Mental Status in the Emergency Department. Semin Neurol. 2019;39(01):005-019. doi:10.1055/s-0038-1677035

   
   

2. Kakuma R, Fort GGD, Arsenault L, et al. Delirium in Older Emergency Department Patients Discharged Home: Effect on Survival. Journal of the American Geriatrics Society. 2003;51(4):443-450. doi:10.1046/j.1532-5415.2003.51151.x

   
   

3. Kanich W, Brady WJ, Huff JS, et al. Altered mental status: Evaluation and etiology in the ED. The American Journal of Emergency Medicine. 2002;20(7):613-617. doi:10.1053/ajem.2002.35464

   
   

4. www.sign.ac.uk – Scottish Intercollegiate Guidelines Network (SIGN). Risk reduction and management of delirium. Edinburgh: SIGN; 2019. (SIGN publication no. 157). [March 2019]. 

   
   

5. Schulz L, Hoffman RJ, Pothof J, Fox B. Top Ten Myths Regarding the Diagnosis and Treatment of Urinary Tract Infections. The Journal of Emergency Medicine. 2016;51(1):25-30. doi:10.1016/j.jemermed.2016.02.009