Coma is defined as a state in which the patient is unresponsive with eyes closed, usually lasting <24 hours. Coma is a medical emergency, and immediate attention/intervention is required for abnormalities in breathing, circulation, glucose, or electrolytes.

• Coma should be differentiated from:
• Lethargy: A patient who is incoherent but arousable and has a tendency to sleep
  • Stupor: A state of excessive somnolence; the patient is responsive only transiently to noxious stimuli
  • Delirium: A confused, agitated patient with fragmented attention, concentration, and memory
  • Vegetative state: Chronic state with clear sleep/wake cycles and no signs of cognition
  • Locked-in: Must be distinguished from coma; cognitive functions are intact, although the patient may appear unconscious

• Be aware of psychogenic coma and locked in states (see “Description”).
• Loss of protective airway reflexes signals impending respiratory failure.