Neurophysiologic assessment of brain maturation after an 8-week trial of skin-to-skin contact on preterm infants☆
Introduction
Neonatal electroencephalographic–polysomnographic studies have been performed for over half a century (Scher, 2006). From the earliest days of the development of the neonatal intensive care unit, EEG-sleep studies have been proposed to assess brain organization and maturation, determine the severity and persistence of a neonatal encephalopathy, detect neonatal seizures, and identify associations with serial clinical examinations and neuroimaging studies. Serial EEG-sleep assessments can include both visual and computer analyses to assess brain organization and maturation (Scher, 2004).
Since the establishment of the modern neonatal intensive care unit, there has been a growing incidence of premature infants. A recently published report estimates that 12.3% of all live births in the United States are children less than 37 weeks gestation (Behrman and Butler, 2006). Altered brain structure and function due to conditions of prematurity have been presented. Such changes may influence long-term outcomes (Isaacs et al., 2003, Scher et al., 2003, Skranes et al., 2007, Srinivasan et al., 2007, Thompson et al., 2007).
Emphasis is now focused on optimizing environmental factors in the neonatal intensive care unit as a form of neuroprotection, particularly light, sound, tactile stimulation and sleep during the long convalescence, in an attempt to shorten hospitalization and improve short-term outcome (Blackburn, 1998, Aucott et al., 2002, Gray and Philbin, 2004). During this extended convalescent time period, environmental alterations include adjustments of light, sound, tactile stimulation and sleep length and quality. The most immature neonates will spend as long as three to four months in the neonatal intensive care unit and are subjected to environmental effects for a longer period of time. Developmentally sensitive care paths for nurses and physicians have been developed to improve ongoing care for neonates as assessed by sleep, growth and age at discharge (Bertelle et al., 2005, Bertelle et al., 2007).
One developmental care path is skin-to-skin contact (SSC) or kangaroo care (Ludington-Hoe et al., 1994, Tessier et al., 2003). Past studies demonstrated that this specific developmental care program promotes physiologic stability and parental–infant interactions to facilitate health and improve short and long-term outcomes (Feldman et al., 2002, Feldman and Eidelman, 2003, Bergman et al., 2004). Developmental care practices for the newborn are supported by experimental evidence that maternal care epigenetically programs stress responses in offspring with later effects on adult behavior (Szyf et al., 2007).
Electroencephalographic/polysomnographic (EEG-sleep) studies are one method by which one can judge the effectiveness of a neuroprotective protocol such as SSC on neonatal brain organization and maturation. Behavioral and neurophysiological parameters must be rigorously defined to accurately assess neonatal sleep state and transitions between active and quiet sleep segments within the sleep cycle. These parameters can then form the basis for comparing neonates with and without therapeutic interventions. For the comparison of SSC and non-SSC cohorts, we have chosen a neurophysiologic approach using serial EEG-polygraphic data files that were submitted for computational analyses.
The purpose of this study was to extend our initial observations (Ludington-Hoe et al., 2006) that a single SSC session at 32 weeks postmenstrual age (PMA) significantly altered EEG-sleep organization in infants assessed. This present study provides evidence that SSC alters neurophysiologic maturation when EEG-sleep studies for a SSC cohort were compared with two non-SSC cohorts using linear and complexity analysis techniques at term ages.
Section snippets
Design
An institutional review board approved a pretest–test, randomized control trial of SSC. Seventy-five preterm infants were evaluated once between October 2002 and June 2004. Longitudinal data for eight infants were collected at both 32 weeks and 40 weeks PMA. Infants in this pilot study were assigned SSC while maintaining the pretest–test randomized assessment for later sleep scoring and analyses as previously described (Ludington-Hoe et al., 2006).
Subjects
Subjects were recruited before PMA of 32 weeks,
Demographic features
Table 1 presents the eight subjects in the SSC group compared to the 126 non-SSC control subjects with respect to gender, gestational age, birthweight, and postmenstrual age at the study time.
Linear measures
The means and standard deviations for the seven linear measures are listed in Table 2A. Five linear measures distinguish the SSC pilot group from the two non-SSC cohorts and consist of fewer REMs (p < .0001), longer sleep cycle lengths (p = .01), higher percentage of quiet sleep (p = .0001), less spectral beta
Discussion
We report more accelerated neurophysiological development for neonates who received skin-to-skin contact (SSC) over an 8-week period using both linear and complexity analyses of EEG-sleep behaviors, compared with two non-SSC cohorts. These behaviors are physiologic surrogates for multiple interconnecting neuronal pathways throughout the neuroaxis within brainstem, diencephalon and cortex which subserve state regulation (Steriade, 2006, Datta and MacLean, 2007, McCarley, 2007). Five specific
Conclusion
The developmental care practice of SSC alters neonatal EEG-sleep organization with accelerated maturation. SSC practices in the neonatal intensive care unit may have an important impact when administered over an extended period on brain maturation involving multiple interconnected neuronal pathways as assessed by computer analyses of EEG-sleep measures.
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Financial support: This study was supported in part by NR04926, NR08587, NS26793 from the National Institutes of Health.