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. 2017 Aug:40:11-14.
doi: 10.1016/j.jcrc.2017.03.002. Epub 2017 Mar 7.

Abnormal environmental light exposure in the intensive care environment

Emily P Fan  1 , Sabra M Abbott  1 , Kathryn J Reid  1 , Phyllis C Zee  1 , Matthew B Maas  2
Affiliations

Abnormal environmental light exposure in the intensive care environment

Emily P Fan et al. J Crit Care. 2017 Aug.

Abstract

Purpose: We sought to characterize ambient light exposure in the intensive care unit (ICU) environment to identify patterns of light exposure relevant to circadian regulation.

Methods: A light monitor was affixed to subjects' bed at eye level in a modern intensive care unit and continuously recorded illuminescence for at least 24h per subject. Blood was sampled hourly and measured for plasma melatonin. Subjects underwent hourly vital sign and bedside neurologic assessments. Care protocols and the ICU environment were not modified for the study.

Results: A total of 67,324 30-second epochs of light data were collected from 17 subjects. Light intensity peaked in the late morning, median 64.1 (interquartile range 19.7-138.7) lux. The 75th percentile of light intensity exceeded 100lx only between 9AM and noon, and never exceeded 150lx. There was no correlation between melatonin amplitude and daytime, nighttime or total light exposure (Spearman's correlation coefficients all <0.2 and p>0.5).

Conclusions: Patients' environmental light exposure in the intensive care unit is consistently low and follows a diurnal pattern. No effect of nighttime light exposure was observed on melatonin secretion. Inadequate daytime light exposure in the ICU may contribute to abnormal circadian rhythms.

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Conflict of interest statement

Conflicts of Interest: All authors report no conflicts of interest.

Figures

Figure 1
Figure 1
Light Exposure in the ICU The median (solid black line) and interquartile range (shaded) of face level illumenescence of ICU subjects is shown for every half hour interval through the day.
Figure 2
Figure 2
Serum Melatonin Profiles The average (solid black line) and individual serum melatonin measurements for ICU subjects through the day is shown.
See this image and copyright information in PMC

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