title: Circadian Rhythm Disruption in the Critically Ill: An Opportunity for Improving Outcomes.
abstract: OBJECTIVE
  Circadian rhythms are severely disrupted among the critically ill. These circadian arrhythmias impair mentation, immunity, autonomic function, endocrine activity, hormonal signaling, and ultimately healing. In this review, we present a modern model of circadian disruption among the critically ill, discuss causes of these circadian arrhythmias, review observational and intervention studies of the effects of circadian-rhythm-restoring factors on medical outcomes, and identify needed key trials of circadian interventions in the critically ill.
  
  
  METHODS
  MEDLINE, EMBASE, PsychINFO, Google Scholar through December 2014.
  
  
  METHODS
  Articles relevant to circadian rhythms, melatonin, and light in the critically ill were selected.
  
  
  METHODS
  Articles were synthesized for this review of circadian arrhythmia and the use of circadian-rhythm-restoring interventions among the critically ill.
  
  
  CONCLUSIONS
  Circadian disruption often demonstrates serial degradation: initially, the amplitude attenuates along with delayed circadian phase. With increasing acuity of illness, circadian rhythmicity may be lost entirely. Causes of chronodisruption may be environmental or internal to the patient. In particular, inadequate daytime illumination and nocturnal light pollution disrupt healthy circadian periodicity. Internal causes of circadian arrhythmia include critical illness itself and subjective experience of distress and pain. Observational studies of windowed rooms and real-time ambient lighting have found that physiologic light-dark patterns may support recovery from critical illness. Studies of early morning bright light or evening melatonin agonists have found improved rates of delirium, enhanced sleep, and lower arrhythmia prevalence. The current evidence base emphasizes that lighting and melatoninergic interventions deserve to be tested in full-scale trials.
authors: All authors: Department of Psychiatry, Psychological Medicine Section, Yale School of Medicine, New Haven, CT.
authors: Mark A
authors: MA
authors: Oldham
authors: Hochang B
authors: HB
authors: Lee
authors: Paul H
authors: PH
authors: Desan
mesh_terms: D021081:Chronobiology Disorders / Q000209:etiology* / Q000628:therapy*; D003422:Critical Care; D016638:Critical Illness; D006801:Humans; D007362:Intensive Care Units; D058996:Quality Improvement; D016896:Treatment Outcome