Elsevier

The Journal of Pediatrics

Volume 162, Issue 2, February 2013, Pages 357-360
The Journal of Pediatrics

Original Article
High Endogenous Melatonin Levels in Critically Ill Children: A Pilot Study

https://doi.org/10.1016/j.jpeds.2012.07.019Get rights and content

Objective

To evaluate the serum melatonin levels in critically ill pediatric patients and to test the effect of light on the melatonin's circadian rhythm. Data on melatonin secretion in critically ill pediatric subjects are lacking.

Study design

We investigated the serum melatonin levels of 16 sedated and mechanically ventilated patients in a pediatric intensive care unit. Children (mean age, 5.1 ± 3.1 years) were randomly assigned to a dark-exposed or to a light-exposed group to evaluate the effects of light on serum melatonin concentrations. Blood samples for serum melatonin analysis were collected at 10 p.m., 1 a.m., 3 a.m., 5 a.m., 8 a.m., and 12 p.m.

Results

The melatonin circadian rhythm was severely disrupted in critically ill children; light exposure lowered serum melatonin even in a context of highly altered circadian cycle; melatonin peaks were greater for healthy age-matched children.

Conclusion

The high melatonin levels in the critically ill children may be a response to counteract the elevated oxidative stress associated with serious diseases. Whether these elevated melatonin levels confer any beneficial effects in pediatric critically ill patients remains unknown.

Section snippets

Methods

This prospective study was conducted in the PICU at University Hospital of Messina between November 2010 and August 2011. Inclusion criteria were as follows: age >1 month, estimated need for invasive mechanical ventilation >2 days. The risk of mortality was assessed by the Pediatric Risk of Mortality (PRISM) score16 and was used to evaluate indirectly the severity of the illness and the need for mechanical ventilation. Children were excluded if their legal guardian refused to participate in the

Results

Sixteen critically ill patients were enrolled. All children were prepuberal. Patients’ characteristics are presented in Table I. All patients were mechanically ventilated and sedated with midazolam (2.3 ± 1.7 μg/kg/min) and fentanyl (2.1 ± 1.7 μg/kg/h).

Melatonin serum peaks in 14 of the 16 patients studied were greater compared with the values reported in the literature for healthy age-matched children.18 As expected, melatonin peaks were greater, although not significantly, in subjects 1-5

Discussion

Melatonin secretion exhibits a strong circadian periodicity closely related to the normal cyclic change between daytime activity and sleep during night.19 Our data confirm that in patients in the ICU, this physiologic pattern is grossly disturbed or is even completely absent. The mechanism behind the disturbed melatonin secretion rhythm in patients in the ICU is unknown but likely depends on various environmental factors as well as factors related to drug therapy and possibly the

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    The authors declare no conflicts of interest.

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