Disruption of Circadian Rhythms and Sleep in Critical Illness and its Impact on the Development of Delirium.

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 risk reduction.