Light affects heart rate's 24‐h rhythmicity in intensive care unit patients: an observational study

Abstract

Background Intensive care unit (ICU) patients experience two affronts to normal 24‐h rhythms: largely internal events such as medication and external factors such as light, noise and nursing interventions. Aims and objectives We investigated the impact of light variance within an ICU on 24‐h rhythmicity of three key physiological parameters: heart rate (HR), mean arterial blood pressure (MAP) and body temperature (BT) in this patient population. Design Patients were assigned to beds either in the ‘light’ or ‘dark’ side within a single ICU. An actigraph continuously recorded light intensity for a 24–72‐h period. Methods Measurements of HR, MAP and BT were recorded every 30 min. Results HR, MAP and BT did not follow 24‐h rhythmicity in all patients. Higher light exposure in the Light Side of the ICU (122·3 versus 50·6 lx) was related to higher HR (89·4 versus 79·8 bpm), which may translate to clinically relevant outcomes in a larger sample. Duration of stay, the one clinical outcome measured in this study, showed no significant variation between the groups (p = 0·147). Conclusions ICU patients are exposed to varying light intensities depending on bed positioning relative to natural sunlight, affecting the 24‐h rhythm of HR. Larger, well‐controlled studies also investigating the effect of relevant light intensity are indicated. Relevance to clinical practice Light is a variable that can be manipulated in the constrained environment of an ICU, thus offering an avenue for relatively unobtrusive interventions.

Rest-Activity Circadian Rhythm and Light Exposure Using Wrist Actigraphy in ICU Patients

“…We found that ACTG maybe useful to record and distinguish the rest-activity circadian rhythms in ICU patients. According to our preliminary data, our ICU light exposure (lux) during daytime and nighttime are within the normal range [7]. Also, M-10 and L-5 measurements in our population are higher, RA is lower and IS, is higher compared to healthy population [3,4].…”

“…This observational study was conducted in a small, single-ward University ICU at a Greek general hospital in Athens, as refereed to a previous study [7]. Generally, total admissions to this ICU are low because the study site is a training hospital without a highdependency unit (HDU), with HDU patients instead assigned to the ICU, resulting in a long mean length of stay.…”

Associations between healthcare environment design and adverse events in intensive care unit

“…Poor environments in ICUs can be potentially inimical for the critically ill patients 23 . Inappropriate lighting has been shown to cause incidents and increased heart rates, indicating the patients are under stress 24,25 . Noise is often still found to be well above the WHO recommendations, resulting in disturbed circadian rhythm and causing delirium in intensive care patients 26,27 .…”

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“…Alterations to melatonin levels are observed in critically ill patients at the intensive care unit (ICU) [8]. Plenty of factors, such as light, noise and interventions pertinent to the ICU environment, have been demonstrated to worsen variability to the 24-h rhythms of many body functions [9]. The 24-h variability of physiological parameters such as heart rate, mean arterial pressure and body temperature are affected [9][10][11].…”

“…Plenty of factors, such as light, noise and interventions pertinent to the ICU environment, have been demonstrated to worsen variability to the 24-h rhythms of many body functions [9]. The 24-h variability of physiological parameters such as heart rate, mean arterial pressure and body temperature are affected [9][10][11]. Furthermore, the critical illness per se and sepsis, which is a clinical state during the stay in the ICU, can lead to circadian dysrhythmia and melatonin variability disturbance, as many studies have demonstrated [12].…”