Abstract
Circadian rhythms are an integral part of life on earth. Circadian rhythms play a
fundamental role in homeostasis as they ensure coordination between the environment
and an organism's behavior and physiology. This coordination is called entrainment.
Entrainment depends on environmental cues known as zeitgebers. Human zeitgebers include
light (primary zeitgeber), sleep, eating, exercise, and activity. Circadian rhythms
are disrupted in critically-ill patients due to both critical illness and current
intensive care unit (ICU) practices. Disruptions in circadian rhythms are tightly
linked with ICU sleep disruption. Together these entities potentiate numerous adverse
outcomes including delirium, metabolic derangements, cardiovascular instability, and
immune compromise. Herein, we will highlight potential areas for care improvement
via chronobundles. We suggest bright light during the day, maintaining darkness, and
protecting sleep at night, intermittent rather than continuous feeds, and activity
via mobilization during the day. Optimizing circadian rhythms is a low-risk intervention
that is underutilized in current ICU practice. This optimization could be a powerful
tool in helping to improve outcomes in the critically-ill patient.
Keywords
circadian rhythm - critical illness - intensive care unit - chronotherapeutics - chronobiology
- sleep - zeitgebers
