Purpose: This article reviews our current understanding of the relationships between critical illness, circadian
disruption, and delirium.
Summary: Delirium is a common and morbid complication of hospitalization, particularly in the setting of critical
illness and intensive care unit (ICU) admission. Critical illness involves a host of acute metabolic, hormonal and
inflammatory responses that appear to disrupt normal sleep architecture and precipitate cerebral dysfunction. The
intervention-heavy environment of the ICU further disrupts normal circadian rhythms and increases delirium risk.
Despite strong evidence for correlation of sleep disruption, critical illness and delirium, causal relationships remain
difficult to prove. Delirium is almost certainly a multifactorial condition. This article reviews proposed pathophysiologic
mechanisms and potential therapeutic targets. In the absence of definitive pharmacologic therapy, interventions
prioritizing maintenance of normal circadian, sleep, and behavioral patterns have shown promise in delirium