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    Altered Mental Status – Delirium

    Cardinal Presentations / Presenting Problems, Neurological, Psychiatric and Behaviour

    Last Updated Dec 13, 2020
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    • 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.

    Diagnostic Process

    • 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.


    • 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).

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