Lung disease and brain development

Altered brain metabolite concentration and delayed neurodevelopment in preterm neonates

BACKGROUND

A very-low-birth-weight (VLBW) preterm infants is associated with an increased risk of impaired neurodevelopmental outcomes. In this study, we investigated how neonatal brain metabolite concentrations changed with postmenstrual age and examined the relationship between changes in concentration (slopes) and neurodevelopmental level at 3-4 years.

METHODS

We retrospectively examined 108 VLBW preterm infants who had brain single-voxel magnetic resonance spectroscopy at 34-42 weeks' postmenstrual age. Neurodevelopment was assessed using a developmental test, and subjects were classified into four groups: developmental quotient <70, 70-84, 85-100, and >100. One-way analyses of covariance and multiple-comparison post hoc tests were used to compare slopes.

RESULTS

We observed correlations between postmenstrual age and the concentrations of N-acetylaspartate and N-acetylaspartylglutamate (tNAA) (p < 0.001); creatine and phosphocreatine (p < 0.001); glutamate and glutamine (p < 0.001); and myo-inositol (p = 0.049) in the deep gray matter; and tNAA (p < 0.001) in the centrum semiovale. A significant interaction was noted among the tNAA slopes of the four groups in the deep gray matter (p = 0.022), and we found a significant difference between the <70 and 85-100 groups (post hoc, p = 0.024).

CONCLUSIONS

In VLBW preterm infants, the slopes of tNAA concentrations (adjusted for postmenstrual age) were associated with lower developmental quotients at 3-4 years.

IMPACT

In very-low-birth-weight preterm-born infants, a slower increase in tNAA brain concentration at term-equivalent age was associated with poorer developmental outcomes at 3-4 years. The increase in tNAA concentration in very-low-birth-weight infants was slower in poorer developmental outcomes, and changes in tNAA concentration appeared to be more critical than changes in tCho for predicting developmental delays. While tNAA/tCho ratios were previously used to examine the correlation with neurodevelopment at 1-2 years, we used brain metabolite concentrations.

An age- and sex-dependent role of catecholaminergic neurons in the control of breathing and hypoxic chemoreflex during postnatal development

The respiratory system undergoes significant development during the postnatal phase. Maturation of brainstem catecholaminergic (CA) neurons is important for the control and modulation of respiratory rhythmogenesis, as well as for chemoreception in early life. We demonstrated an inhibitory role for CA neurons in CO₂ chemosensitivity in neonatal and juvenile male and female rats, but information regarding their role in the hypoxic ventilatory response (HVR) is lacking. We evaluated the contribution of brainstem CA neurons in the HVR during postnatal (P) development (P7-8, P14-15 and P20-21) in male and female rats through chemical injury with conjugated saporin anti-dopamine beta-hydroxylase (DβH-SAP, 420 ng·μL^-1) injected in the fourth ventricle. Ventilation (V̇_E) and oxygen consumption were recorded one week after the lesion in unanesthetized rats during exposure to normoxia and hypoxia. Hypoxia reduced breathing variability in P7-8 control rats of both sexes. At P7-8, the HVR for lesioned males and females increased 27% and 24%, respectively. Additionally, the lesion reduced the normoxic breathing variability in both sexes at P7-8, but hypoxia partially reverted this effect. For P14-15, the increase in V̇_E during hypoxia was 30% higher for male and 24% higher for female lesioned animals. A sex-specific difference was detected at P20-21, as lesioned males exhibited a 24% decrease in the HVR, while lesioned females experienced a 22% increase. Furthermore, the hypoxia-induced body temperature reduction was attenuated in P20-21 lesioned females. We conclude that brainstem CA neurons modulate the HRV during the postnatal phase, and possibly thermoregulation during hypoxia.

Oxygen Sensing in Early Life

From birth, animals should possess functional machinery to appropriately regulate its respiration. This machinery has to detect the available oxygen quantity in order to efficiently modulate breathing movements in accordance with body requirements. The chemosensitivity process responsible for this detection is known to be mainly performed by carotid bodies. However, pulmonary neuroendocrine cells, which are mainly gathered in neuroepithelial bodies, also present the capability to exert chemosensitivity. The goal of this article is to put in perspective the potential complementarity in the activity of these two peripheral chemosensors in the context of neonatal oxygen chemosensitivity.

Understanding the sequence of pulmonary injury in the extremely low birth weight, surfactant-deficient infant

Human lung development begins around day 26 postconception and continues throughout early childhood. Many crucial events can affect this delicate tissue as it develops, leading to altered and abnormal growth and development of the lungs, thereby yielding a variety of morbidities and sometimes even mortality. Understanding the pathophysiology of lung injury in the extremely low birth weight neonate is essential when caring for these infants, especially during the first hours of life. This article provides bedside clinicians with foundational information related to acute lung injury and the sequence of events that can ultimately lead to neonatal chronic lung disease and bronchopulmonary dysplasia.

Perinatal assessment of infant, parents, and parent-infant relationship: prematurity as an example

This article reviews the stresses for parents, infants, and other caregivers during the period surrounding the birth of the premature infant. Principles of assessment of infant discomfort, parental stress, the parent-infant relationship, and the match of the medical caregiving environment to the individual infant's needs are discussed. Relevant tools to aide in these aspects of assessment are reviewed. The role of early assessment as preventive intervention and the indication for subsequent intervention in complicated cases of premature infants and their parents are further discussed. The article offers detailed clinical examples to illustrate these and other points throughout.