Refers to impaired mental cognition, decreased attention and awareness, or altered consciousness level.
Causes can be categorized as structural, infectious, inflammatory, toxic, metabolic and paroxysmal (Lehan RK, Mink J).
Causes include: medications, infections, metabolic disorders, trauma, malignancy, drug abuse, and stroke.
Consciousness in normal adults is lost at PO2 ∼27 mmHg and PCO2 levels between 90 and 120 mmHg
Common disorders are infections, electrolyte abnormalities, hypoglycemia, drug affects, diseases of the thyroid, kidneys, liver and central nervous system.
Rare causes include paraneoplastic syndromes, and porphyria.
Accounts for 4-10% of chief complaints at emergency departments (Kanich W).
10-50% of hospitalized have acute altered mental status.
AMS accounts for a significant number of in hospital neurological consultations.
History and physical exam essential to establish cause.
This is a high rate of electrographic seizures in a general inpatient population with altered mental status as the indication for EEG (Betjermann JP et al).