Alterations in Consciousness

Alterations in Consciousness is a topic covered in the Washington Manual of Medical Therapeutics.

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General Principles


  • Coma is a state of complete behavioral unresponsiveness to external stimulation. Evaluation and treatment should be performed concurrently and expeditiously because multiple etiologies can lead to irreversible brain damage. The need for neurosurgical intervention must be determined promptly.
  • Delirium is an acute state of confusion that can result from diffuse or multifocal cerebral dysfunction and is characterized by relatively rapid reduction in the ability to focus, sustain, or shift attention. Changes in cognition, fluctuations in consciousness, disorientation, and even hallucinations are common.


  • About 30% of patients over 60% and 80% of ICU patients experience delirium during hospitalization.
  • Delirious patients often have prolonged stays and are at greater risk for subsequent cognitive decline.


  • Coma results from diffuse or multifocal dysfunction that involves both cerebral hemispheres and the reticular activating system in the brainstem.
  • Etiologies of altered mental status are listed in Table 27-1.
    Table 27-1: Causes of Altered Mental Status
    Metabolic derangements/diffuse etiologies
    • Hypernatremia/hyponatremia
    • Hypercalcemia
    • Hyperglycemia/hypoglycemia
    • Hyperthyroidism/hypothyroidism
    • Acute intermittent porphyria
    • Hypertensive encephalopathy/reversible posterior leukoencephalopathy
    • Hypoxia/hypercapnia
    • Global cerebral ischemia from hypotension
    • Meningitis/encephalitis
    • Sepsis
    • Systemic infections with spread to CNS
    • Prescription medications and side effects of medications
    • Drugs of abuse
    • Withdrawal situations
    • Medication side effects
    • Inhaled toxins
    Inborn errors of metabolism
    Nutritional deficiency (i.e., thiamine)
    • Subclinical seizures
    • Postictal state
    Head trauma
    • Ischemic stroke (only certain stroke locations cause altered mental status)
    • Hemorrhage
    • Hydrocephalus
    • Tumor
    Systemic organ failure
    • Hepatic failure
    • Renal failure
    • Vasculitis (primary CNS or systemic)
    • Encephalitis
    • Autoantibody-mediated encephalopathies (e.g., anti–voltage-gated potassium channel complex antibodies such as anti-Lgi-1 and anti-Caspr-2)

    CNS, central nervous system.

  • Mild systemic illness (e.g., urinary tract infections), introduction of new medications, fever, and/or sleep deprivation are common causes of delirium in the elderly and patients with chronic central nervous system (CNS) dysfunction of any etiology.

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