Delirium - A Dysfunctional Circadian Rhythm

Critical care units are a major cause of a disrupted circadian rhythm in patients [1, 2]. Light, noise, treatments, sedatives and mechanical ventilation throughout a 24 h time period are the major offenders of circadian rhythm disruption in the intensive care unit [ICU] [2]. Interestingly, circadian disruption is frequently associated with the occurrence of delirium having a high impact on outcome and mortality in the critically ill [3-5]. Endogenous melatonin, a mirror of our circadian rhythm, seems to play an important role in the development of delirium in critical ill patients. Critically ill patients have been found to have abnormal melatonin levels indicating a disrupted circadian rhythm [6, 7]. Thus, results on melatonin expression in critical ill patients have generated a new interest in the use of exogenous melatonin and melatonin agonists to improve sleep, cognitive function or delirium. In fact, a very elegant randomized controlled trial recently demonstrated effectiveness in the use of a melatonin agonist (Ramelteon) versus placebo in the prevention of delirium