Effects of nursery illumination on frequency of eyelid opening and state in preterm neonates

Cycled Lighting Versus Continuous Near Darkness in Preterm Infants: A Randomized Controlled Trial

OBJECTIVE

To compare the effectiveness of cycled lighting (CL) or continuous near darkness (CND) on weight in preterm infants.

STUDY DESIGN

Total 147 infants with a gestational age 25-32 weeks and/or a birth weight 750-1500 g were included in the study. The infants were classified into two groups: CL and CND. Weight on postnatal day 14, weight at corrected 35 weeks, mean rectal temperature and serum growth hormone, cortisol, melatonin levels at 35 weeks' post menstrual age (PMA), weekly weight gain, full enteral feeding time, duration of mechanical ventilation, retinopathy of prematurity (ROP), length of stay in the hospital, weight and length at three and six months corrected age were compared between the groups.

RESULTS

There were no differences between weights on postnatal day 14. Anthropometric parameters and mean rectal temperatures of groups also were not different at 35 weeks' PMA. There were no differences among the groups in duration of full enteral feeding time, length of stay in hospitalization, duration of mechanical ventilation, ROP and anthropometric parameters. Further, serum growth hormone, cortisol, and melatonin levels were similar between the groups at 35 weeks' PMA.

CONCLUSION

CL and CND did not have any advantages over each other.

Observational study found that even small variations in light can wake up very preterm infants in a neonatal intensive care unit

AIM

This prospective observational study evaluated the behavioural responses of very preterm infants to spontaneous light variations.

METHODS

We measured spontaneous light variations in the incubators of 27 very preterm infants, with a median gestational age of 28 weeks (range 26-31 weeks), over 10 hours. All of them had been admitted to the neonatal care unit of the Strasbourg University Hospital, France, between April 2008 and July 2009. Two independent raters examined changes in the infants' behavioural states using video recordings. The percentage of awakenings was recorded when there were light variations and during control periods with no changes.

RESULTS

We analysed 275 periods following light variations and 275 control periods. The overall percentage of awakenings was greater during periods following a change in light than during control periods (16.3% vs 11%, p = 0.03). The extent of light protection affected the percentage of awakenings. In mild light protection, there were more awakenings following changes in light than in control periods (25.6% vs 6.7%, p = 0.01). This difference was not found in high light protection.

CONCLUSION

Very preterm infants can be woken up by small variations in light, when the light protection in their incubator is insufficient.

The development of potentially better practices to support the neurodevelopment of infants in the NICU

OBJECTIVE

To review the existing evidence used to identify potentially better care practices that support newborn brain development.

STUDY DESIGN

Literature review.

RESULT

Sixteen potentially better practices are identified and grouped into two operational clinical bundles based upon timing for recommended implementation.

CONCLUSION

Existing evidence supports the implementation of selected care practices that potentially may support newborn brain development.

Sleep in the neonatal intensive care unit

Recent experimental data suggest a strong role for sleep in brain development. As sleep is the predominant behavioral state in the term and especially the preterm newborn, these data underline the importance of respecting sleep duration and organization within the different sleep states. Polysomnography is the preferred technique used for identification of sleep state; however, behavioral observations-under the condition that the observer is well trained-may prove as efficient. Newborns hospitalized in the neonatal intensive care unit are exposed to many stimuli and care activities that disrupt their sleep organization and may have irreversible effects on their brain development. In order to improve the long-term neurobehavioral outcome of these high-risk subjects, a consistent care approach is proposed. Application of the Neonatal Individualized Developmental Care and Assessment Program decreases environmental stressful events and promotes harmonious well-being behaviors, based on an individual approach. This strategy has encouraging results, showing an increase in sleep duration under Neonatal Individualized Developmental Care and Assessment Program conditions, but further studies are needed to assess its long-term neurobehavioral impact.

Environmental light and the preterm infant

The lighting environment of the preterm baby is quite unlike that experienced at any other time of life. Physical and physiological factors control how much light reaches the retina of the preterm baby. With respect to the former, although many neonatal intensive care units are brightly and continuously lit, there is a trend to employ lower levels of illumination and to introduce cycling regimens. Physiological determinants of the retinal light dose include: eyelid opening and transmission, pupil diameter and the transmission characteristics of the ocular media. Early exposure to light does not significantly hasten or retard normal visual development, and it is not a factor in the development of retinopathy of prematurity. However, ambient neonatal intensive care unit illumination may be implicated in some of the more subtle visual pathway sequelae that cannot be attributed to other major complications of preterm birth including altered visual functions and arrested eye growth.

Effects on oxygen saturation levels of handling premature infants within the concepts of kinaesthetic infant handling: pilot study

Preterm infants are exposed to many stressors within the neonatal intensive care environment. Since these are associated with medical and developmental problems, a reduction of stress factors is desirable. Handling is a very common occurrence and is associated with stress. Kinaesthetic infant handling (KIH) offers practical guidance on handling for nurses and has been widely implemented in Germany, although there is no direct experimental evidence to support its use. The findings of this pilot study suggest a beneficial effect on the SpO2 for infants who were handled using KIH. Since this was a pilot study with a small sample size, caution has to be exercised with this finding. Therefore, the main purpose of the study was: (1) to identify the weaknesses and strengths of the chosen study design; and (2) to perform a power analysis in order to determine a sufficient sample size for the full experiment.

Effect of standard rest periods on convalescent preterm infants

OBJECTIVE

To examine the effects of standardized rest periods on the sleep-wake states of preterm infants who were convalescing.

DESIGN

A randomized experimental study conducted from time of infants' entry into intermediate care until their discharge from the hospital. Because subjects' time in this study varied, data were analyzed cross-sectionally using the observation made between 5-11 days of the study and longitudinally over 3 weeks using a subset of subjects.

SETTING

The intermediate care nursery of a tertiary care hospital.

SUBJECTS

Forty-six preterm infants (23 matched pairs). A subset of 12 pairs, in which infants in the experimental and the control groups were in the study for 3 weeks, was analyzed longitudinally.

INTERVENTIONS

Four standardized rest periods each day.

MAIN OUTCOME MEASURES

Infants were observed once a week between noon and 8 p.m. Three sleep-wake states--quiet awake, active, and sleep--were measured as percentages of the naps and total observation.

RESULTS

Within 5 days, infants in the experimental group exhibited more sleep (F[1,44] = 2.37, p < 0.05) and less active states (F[1,44] = 3.06, p < 0.01) during nap time. Infants receiving the intervention for 3 weeks had more sleep (F[1,22] = 4.63, p < 0.05) and less quiet waking states (F[1,22] = 13.85, p < 0.01) during naps. State patterns over the entire observation did not differ between the groups at 5 days, but by 3 weeks, infants in the experimental group had less quiet waking (F[1,22] = 17.44, p < 0.001) and longer uninterrupted sleep bouts (F[1,22] = 5.19, p < 0.05).

CONCLUSIONS

A simple modification of nursing care had an impact on the sleeping and waking states of preterm infants.

Light and the neonatal eye

The lighting environment where the baby born prematurely is placed is different from that experienced in utero. As early exposure to light may affect the immature visual system we have attempted to quantify the neonatal ocular light dose. Lighting surveys performed in 7 neonatal units (NNUs) suggested that mean unit illuminance was 470 lux (range 192-890 lux) and intensive care areas within the NNU were significantly brighter than their corresponding low dependency nurseries. The spectral power distribution of fluorescent lights in NNUs was weighted towards the blue end of the spectrum. Datalogging studies demonstrated that between about 30% and 98% of environmental light was incident on the eyelid, which acts as a predominantly red-pass filter, permitting 21% transmission at 700 nm with less than or equal to 5% transmission at 580 nm. Eye-lid opening frequency was quantified: 45% less than or equal to 26 weeks gestational age and decreasing to 7% at 28 weeks gestational age. The onset of the pupillary reflex to light was between 30 and 34 weeks postmenstrual age, the mean diameter was 3.46 mm before this event and 3.02 mm afterwards. Retinal irradiance values calculated from these data show that it is a function of postmenstrual age. Further studies are required to determine its effect on the immature visual system.

Light and the immature visual system

Preterm neonates are cared for in an environment which is continuously and brightly lit, and is very different to that experienced at any other time of life. The amount of light reaching the neonatal eye is governed by two groups of factors. Physical factors include intensity, spectral characteristics and duration of light exposure. Physiological factors are: Frequency of eyelid opening, transmission of light through the closed eyelid, pupil reactivity and area, transmission by the ocular tissues and retinal surface area. Retinal irradiance declines with increasing postmenstrual age. Mechanisms by which light may affect the neonatal eye and clinical conditions in which light have been implicated are considered.

Eyelid opening in preterm neonates

The frequency and patterns of eyelid opening were examined in a group of neonates (gestational age 24-35 weeks). Observations were spread over the 24 hour period to obtain a complete pattern of events. Mean eyelid closure was 74%. When babies were grouped by gestational age, however, differences became apparent, babies of less than 26 weeks having their eyes shut for only 55% of observations compared with 93% at 28 weeks. Trend analysis confirmed that eyelid closure reached a peak at 28 weeks. Neonates exposed to a day/night regimen, opened their eyes significantly more than those exposed to continuous illumination. We suggest that frequency of eyelid opening may be related both to the infant's developmental state (postmenstrual age) and the illumination of the neonatal unit. Frequency of eyelid opening should therefore be considered when calculating the ocular light exposure of preterm neonates.

Light transmission through the human eyelid: in vivo measurement

We describe an in vivo measurement technique for determining the transmission of light through the human eyelid and present data from three human subjects. The relevance of the transmission measurements are discussed in relation to (1) clinical electrophysiology and (2) the effects of light on the developing visual system.