Brain injury in chronically ventilated preterm neonates: collateral damage related to ventilation strategy

Baby breaths: Honoring Kurt Albertine and his contributions to respiratory research in young mammals and to The Anatomical Record

In January 2021, Kurt Albertine, PhD, stepped down as the Editor of The Anatomical Record after 15 years of dedicated service. As Editor-In-Chief, he oversaw incredible growth, expanded scope, and increased impact of the journal. At the same time, he directed an active research lab in neonatal pulmonary biology at the University of Utah, with an exceptional track record of mentoring students, fellows, clinicians, and junior faculty. This special issue of The Anatomical Record honors Kurt's contributions to the journal, as well as to the fields of respiratory anatomy, physiology, and neonatology. Several of the invited papers were contributed by Kurt's collaborators and former trainees who cover topics related to neonatal lamb development, bronchopulmonary dysplasia, postnatal lung pathology, respiratory physiology, and the relationship of anatomy to function. Additional papers relating to Kurt's passion for dinosaur anatomy and human embryonic anatomy based on the Kyoto Collection of Human Embryos and Fetuses. Kurt's tireless enthusiasm for the journal and devotion to the field are reflected in the papers in this special issue in his honor. His tenure at the journal was transformative and provided a foundation for continued growth and impact in anatomical sciences research from dinosaurs to clinical applications in humans. We celebrate Kurt's accomplishments and broader impact on anatomical sciences in this Special Issue of The Anatomical Record.

Surfactant administration and cerebral oxygenation and perfusion in preterm neonates - A systematic review of literature

BACKGROUND

Surfactant replacement is standard for preterm neonates with respiratory distress syndrome, improving survival and outcomes. Less invasive surfactant administration (LISA) and intubation-surfactant-extubation (INSURE) are preferred methods for surfactant replacement in spontaneously breathing preterm neonates. Despite the undeniable benefits of surfactant implementation in neonatal care, surfactant administration can affect vital parameters and cerebral oxygenation and perfusion, assessed by near-infrared spectroscopy (NIRS).

OBJECTIVE

This review systematically examined the literature on surfactant administration in preterm neonates and its impact on NIRS-measured cerebral oxygenation.

METHODS

A systematic search of PubMed, Embase, CINAHL, Clinical Trials, and Ovid Medline was conducted using following terms: newborn, infant, neonate, preterm, premature, prematurity, surfactant, LISA, less-invasive surfactant administration, INSURE, near-infrared-spectroscopy, NIRS, oximetry, spectroscopy, cerebral oxygenation, cerebral tissue oxygen saturation (crSO2), crSO2, cerebral perfusion. Only studies in human preterm neonates were included.

RESULTS

Sixteen studies were identified that described cerebral oxygenation measured by NIRS in the context of surfactant administration demonstrating a decrease in crSO2 during surfactant administration, followed by a subsequent increase. Three studies specifically described the course of crSO2 in neonates while receiving LISA, whereby in two of these LISA was compared to INSURE describing differences in crSO2 behaviour. Two additional studies described surfactant administration using the INSURE procedure and the influence on cerebral oxygenation. Ten studies investigated surfactant administration in intubated neonates receiving mechanical ventilation. One study described crSO2 in neonates receiving aerosolised surfactant.

CONCLUSION

This systematic review indicates that surfactant administration is associated with a transient decrease in crSO2 followed by a return to baseline levels, whereby differences between the LISA and INSURE methods were observed.

Brain age predicted using graph convolutional neural network explains neurodevelopmental trajectory in preterm neonates

OBJECTIVES

Dramatic brain morphological changes occur throughout the third trimester of gestation. In this study, we investigated whether the predicted brain age (PBA) derived from graph convolutional network (GCN) that accounts for cortical morphometrics in third trimester is associated with postnatal abnormalities and neurodevelopmental outcome.

METHODS

In total, 577 T1 MRI scans of preterm neonates from two different datasets were analyzed; the NEOCIVET pipeline generated cortical surfaces and morphological features, which were then fed to the GCN to predict brain age. The brain age index (BAI; PBA minus chronological age) was used to determine the relationships among preterm birth (i.e., birthweight and birth age), perinatal brain injuries, postnatal events/clinical conditions, BAI at postnatal scan, and neurodevelopmental scores at 30 months.

RESULTS

Brain morphology and GCN-based age prediction of preterm neonates without brain lesions (mean absolute error [MAE]: 0.96 weeks) outperformed conventional machine learning methods using no topological information. Structural equation models (SEM) showed that BAI mediated the influence of preterm birth and postnatal clinical factors, but not perinatal brain injuries, on neurodevelopmental outcome at 30 months of age.

CONCLUSIONS

Brain morphology may be clinically meaningful in measuring brain age, as it relates to postnatal factors, and predicting neurodevelopmental outcome.

CLINICAL RELEVANCE STATEMENT

Understanding the neurodevelopmental trajectory of preterm neonates through the prediction of brain age using a graph convolutional neural network may allow for earlier detection of potential developmental abnormalities and improved interventions, consequently enhancing the prognosis and quality of life in this vulnerable population.

KEY POINTS

•Brain age in preterm neonates predicted using a graph convolutional network with brain morphological changes mediates the pre-scan risk factors and post-scan neurodevelopmental outcomes. •Predicted brain age oriented from conventional deep learning approaches, which indicates the neurodevelopmental status in neonates, shows a lack of sensitivity to perinatal risk factors and predicting neurodevelopmental outcomes. •The new brain age index based on brain morphology and graph convolutional network enhances the accuracy and clinical interpretation of predicted brain age for neonates.

Delineating morbidity patterns in preterm infants at near-term age using a data-driven approach

BACKGROUND

Long-term survival after premature birth is significantly determined by development of morbidities, primarily affecting the cardio-respiratory or central nervous system. Existing studies are limited to pairwise morbidity associations, thereby lacking a holistic understanding of morbidity co-occurrence and respective risk profiles.

METHODS

Our study, for the first time, aimed at delineating and characterizing morbidity profiles at near-term age and investigated the most prevalent morbidities in preterm infants: bronchopulmonary dysplasia (BPD), pulmonary hypertension (PH), mild cardiac defects, perinatal brain pathology and retinopathy of prematurity (ROP). For analysis, we employed two independent, prospective cohorts, comprising a total of 530 very preterm infants: AIRR ("Attention to Infants at Respiratory Risks") and NEuroSIS ("Neonatal European Study of Inhaled Steroids"). Using a data-driven strategy, we successfully characterized morbidity profiles of preterm infants in a stepwise approach and (1) quantified pairwise morbidity correlations, (2) assessed the discriminatory power of BPD (complemented by imaging-based structural and functional lung phenotyping) in relation to these morbidities, (3) investigated collective co-occurrence patterns, and (4) identified infant subgroups who share similar morbidity profiles using machine learning techniques.

RESULTS

First, we showed that, in line with pathophysiologic understanding, BPD and ROP have the highest pairwise correlation, followed by BPD and PH as well as BPD and mild cardiac defects. Second, we revealed that BPD exhibits only limited capacity in discriminating morbidity occurrence, despite its prevalence and clinical indication as a driver of comorbidities. Further, we demonstrated that structural and functional lung phenotyping did not exhibit higher association with morbidity severity than BPD. Lastly, we identified patient clusters that share similar morbidity patterns using machine learning in AIRR (n=6 clusters) and NEuroSIS (n=8 clusters).

CONCLUSIONS

By capturing correlations as well as more complex morbidity relations, we provided a comprehensive characterization of morbidity profiles at discharge, linked to shared disease pathophysiology. Future studies could benefit from identifying risk profiles to thereby develop personalized monitoring strategies.

TRIAL REGISTRATION

AIRR: DRKS.de, DRKS00004600, 28/01/2013. NEuroSIS: ClinicalTrials.gov, NCT01035190, 18/12/2009.

Preterm lung and brain responses to mechanical ventilation and corticosteroids

Mechanical ventilation is necessary to maintain oxygenation and ventilation in many preterm infants. Unfortunately, even short periods of mechanical ventilation can cause lung and airway injury, and initiate the lung inflammation that contributes to the development of bronchopulmonary dysplasia (BPD). The mechanical stretch leads to airway cell differentiation and simplification of the alveoli, and releases cytokines that cause systemic response in other organs. Mechanical ventilation also leads to brain injury (IVH, white and gray matter) and neuronal inflammation that can affect the neurodevelopment of preterm infants. In efforts to decrease BPD, corticosteroids have been used for both prevention and treatment of lung inflammation. Corticosteroids have also been demonstrated to cause neuronal injury, so the clinician must balance the negative effects of both mechanical ventilation and steroids on the brain and lungs. Predictive models for BPD can help assess the infants who will benefit most from corticosteroid exposure. This review describes the lung and brain injury from mechanical ventilation in the delivery room and chronic mechanical ventilation in animal models. It provides updates on the current guidelines for use of postnatal corticosteroids (dexamethasone, hydrocortisone, budesonide, budesonide with surfactant) for the prevention and treatment of BPD, and the effects the timing of each steroid regimen has on neurodevelopment.

Neurodevelopmental outcome of Italian preterm ELBW infants: an eleven years single center cohort

BACKGROUND

Preterm extremely low birth weight infants (ELBWi) are known to be at greater risk of developing neuropsychiatric diseases. Identifying early predictors of outcome is essential to refer patients for early intervention. Few studies have investigated neurodevelopmental outcomes in Italian ELBWi. This study aims to describe neurodevelopmental outcome at 24 months of corrected age in an eleven-year single-center cohort of Italian ELBWi and to identify early risk factors for adverse neurodevelopmental outcomes.

METHODS

All infants born with birth weight < 1000 g and admitted to the Neonatal Intensive Care Unit of the "Fondazione IRCCS Policlinico San Matteo" hospital in Pavia, Italy, from Jan 1, 2005 to Dec 31, 2015 were eligible for inclusion. At 24 months, Griffiths' Mental Developmental Scales Extended Revised (GMDS-ER) were administered. Neurodevelopmental outcome was classified as: normal, minor sequelae (minor neurological signs, General Quotient between 76 and 87), major sequelae (cerebral palsy; General Quotient ≤ 75; severe sensory impairment). Univariate and multivariate multinomial logistic regression models were performed to analyze the correlation between neonatal variables and neurodevelopmental outcome.

RESULTS

176 ELBWi were enrolled (mean gestational age 26.52 weeks sd2.23; mean birthweight 777.45 g sd142.89). 67% showed a normal outcome at 24 months, 17% minor sequelae and 16% major sequelae (4.6% cerebral palsy on overall sample). The most frequent major sequela was cognitive impairment (8.52%). In the entire sample the median score on the Hearing-Speech subscale was lower than the median scores recorded on the other subscales and showed a significantly weaker correlation to each of the other subscales of the GMDS-ER. Severely abnormal cUS findings (RRR 10.22 p 0.043) and bronchopulmonary dysplasia (RRR 4.36 p 0.008) were independent risk factors for major sequelae and bronchopulmonary dysplasia for minor sequelae (RRR 3.00 p 0.018) on multivariate multinomial logistic regression.

CONCLUSIONS

This study showed an improvement in ELBWI survival rate without neurodevelopmental impairment at 24 months compared to previously reported international cohorts. Cognitive impairment was the most frequent major sequela. Median scores on GMDS-ER showed a peculiar developmental profile characterized by a selective deficit in the language domain. Severely abnormal cUS findings and bronchopulmonary dysplasia were confirmed as independent risk factors for major sequelae.

White Matter Injury in Preterm Infants: Pathogenesis and Potential Therapy From the Aspect of the Gut–Brain Axis

Very preterm infants who survive are at high risk of white matter injury (WMI). With a greater understanding of the pathogenesis of WMI, the gut microbiota has recently drawn increasing attention in this field. This review tries to clarify the possible mechanisms behind the communication of the gut bacteria and the immature brain via the gut–brain axis. The gut microbiota releases signals, such as microbial metabolites. These metabolites regulate inflammatory and immune responses characterized by microglial activation, which ultimately impact the differentiation of pre-myelinating oligodendrocytes (pre-OLs) and lead to WMI. Moreover, probiotics and prebiotics emerge as a promising therapy to improve the neurodevelopmental outcome. However, future studies are required to clarify the function of these above products and the optimal time for their administration within a larger population. Based on the existing evidence, it is still too early to recommend probiotics and prebiotics as effective treatments for WMI.

Bronchopulmonary dysplasia precursors influence risk of white matter injury and adverse neurodevelopmental outcome in preterm infants

BACKGROUND

Cumulative supplemental oxygen (CSO) and cumulative mean airway pressure (CMAP) are associated with bronchopulmonary dysplasia (BPD) in preterm infants, but their relationships to white matter injury (WMI) and neurodevelopment have not been evaluated.

METHODS

Preterm infants <32 weeks' gestation were prospectively imaged with 3 T MRI near term. CSO and CMAP were retrospectively summed over the first 14 and 28 days. Neurodevelopment was assessed at 30 months adjusted using the Bayley-III. ROC and linear regression were used to evaluate the relationship between CSO, CMAP, and BPD with WMI and neurodevelopmental performance, respectively.

RESULTS

Of the 87 infants, 30 (34.5%) had moderate-severe BPD, which was associated with WMI (OR 5.5, 95% CI 1.1-34.9, p = 0.012). CSO and CMAP predicted WMI as well as BPD (AUC 0.68-0.77). CSO was independently associated with decreased language and cognitive performance (mean difference at 14 days: -11.0, 95% CI -19.8 to -2.2, p = 0.015 and -9.8, 95% CI -18.9 to -0.7, p = 0.035, respectively) at 30 months adjusted.

CONCLUSIONS

BPD precursors predict WMI as well as BPD. Cumulative supplemental oxygen over the first 14 days of life is independently associated with lower language and cognitive performances. These data suggest that early respiratory status influences the risk of adverse neurodevelopment in preterm infants.

IMPACT

Respiratory precursors to bronchopulmonary dysplasia (BPD), cumulative supplemental oxygen and mean airway pressure, over the first 14-28 days performed as well as BPD for the prediction of white matter injury on MRI in preterm infants. Cumulative supplemental oxygen was independently associated with lower language and cognitive performance on the Bayley-III at 30 months adjusted. These data suggest that early respiratory status may help explain why BPD is independently associated with adverse neurodevelopmental outcomes in the preterm population and highlights the importance of interventions targeting respiratory status as a potential avenue to improve neurodevelopmental outcomes.

Increased peak end-expiratory pressure in ventilated preterm lambs changes cerebral microvascular perfusion: direct synchrotron microangiography assessment

Positive end-expiratory pressure (PEEP) improves oxygenation in mechanically ventilated preterm neonates by preventing lung collapse. However, high PEEP may alter cerebral blood flow secondarily to the increased intrathoracic pressure, predisposing to brain injury. The precise effects of high PEEP on cerebral hemodynamics in the preterm brain are unknown. We aimed to assess the effect of PEEP on microvessels in the preterm brain by using synchrotron radiation (SR) microangiography, which enables in vivo real-time high-resolution imaging of the cerebral vasculature. Preterm lambs (0.8 gestation, n = 4) were delivered via caesarean section, anesthetized, and ventilated. SR microangiography of the right cerebral hemisphere was performed with iodine contrast administered into the right carotid artery during PEEP ventilation of 5 and 10 cmH₂O. Carotid blood flow was measured using an ultrasonic flow probe placed around the left carotid artery. An increase of PEEP from 5 to 10 cmH₂O increased the diameter of small cerebral vessels (<150 µm) but decreased the diameter of larger cerebral vessels (>500 µm) in all four lambs. Additionally, the higher PEEP increased the cerebral contrast transit time in three of the four lambs. Carotid blood flow increased in two lambs, which also had increased carbon dioxide levels during PEEP 10. Our results suggest that PEEP of 10 cmH₂O alters the preterm cerebral hemodynamics, with prolonged cerebral blood flow transit and engorgement of small cerebral microvessels likely due to the increased intrathoracic pressure. These microvascular changes are generally not reflected in global assessment of cerebral blood flow or oxygenation.NEW & NOTEWORTHY An increase of positive end-expiratory pressure (PEEP) from 5 to 10 cmH₂O increased the diameter of small cerebral vessels (<150 µm) but decreased the diameter of larger cerebral vessels (>500 µm). This suggests increased intrathoracic pressure due to high PEEP can drive microvessel engorgement in the preterm brain, which may play a role in cerebrovascular injury.

Respiratory Support of the Preterm Neonate: Lessons About Ventilation-Induced Brain Injury From Large Animal Models

Many preterm neonates require mechanical ventilation which increases the risk of cerebral inflammation and white matter injury in the immature brain. In this review, we discuss the links between ventilation and brain injury with a focus on the immediate period after birth, incorporating respiratory support in the delivery room and subsequent mechanical ventilation in the neonatal intensive care unit. This review collates insight from large animal models in which acute injurious ventilation and prolonged periods of ventilation have been used to create clinically relevant brain injury patterns. These models are valuable resources in investigating the pathophysiology of ventilation-induced brain injury and have important translational implications. We discuss the challenges of reconciling lung and brain maturation in commonly used large animal models. A comprehensive understanding of ventilation-induced brain injury is necessary to guide the way we care for preterm neonates, with the goal to improve their neurodevelopmental outcomes.

Cognitive Development and Quality of Life Associated With BPD in 10-Year-Olds Born Preterm

OBJECTIVES

To compare neurocognitive, language, executive function, academic achievement, neurologic and behavioral outcomes, and quality of life at age 10 years in children born extremely preterm who developed bronchopulmonary dysplasia (BPD) to children who did not develop BPD.

METHODS

The Extremely Low Gestational Age Newborns study population included 863 children born extremely preterm whose BPD status before discharge was known had an IQ (Differential Ability Scales II [DAS II]) assessment at 10 years. We evaluated the association of BPD with any cognitive (DAS II), executive function (NEuroPSYchological Assessment II), academic achievement (Wechsler Individual Achievement Test-III and Oral and Written Language Scales [OWLS]) as well as social dysfunctions (Social Responsiveness Scale). We used logistic regression models, adjusting for potential confounding factors, to assess the strength of association between the severity of BPD and each outcomes.

RESULTS

Three hundred and seventy-two (43%) children were oxygen-dependent at 36 weeks postconception age, whereas an additional 78 (9%) were also oxygen- and ventilator-dependent. IQ scores 2 or more SDs below the expected mean (ie, z scores ≤-2) occurred twice as commonly among children who had BPD as among those who did not. Children with severe BPD consistently had the lowest scores on DAS II, OWLS, Wechsler Individual Achievement Test-III, NEuroPSYchological Assessment II, and Social Responsiveness Scale assessments.

CONCLUSIONS

Among 10-year-old children born extremely preterm, those who had BPD were at increased risk of cognitive, language, and executive dysfunctions; academic achievement limitations; social skill deficits; and low scores on assessments of health-related quality of life.

Early detection of neonatal hypoxic-ischemic white matter injury: an MR diffusion tensor imaging study

The purpose of this study was to compare diffusion tensor metrics in normal age-matched neonates with survivors of hypoxic–ischemic encephalopathy (HIE) and extracorporeal membrane oxygenation (ECMO). Thirty-five normal, 27 HIE, and 13 ECMO infants underwent MRI at 3 T. Neurodevelopmental assessments were performed. Fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD) of the inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, anterior commissure, genu corpus callosum and splenium of the corpus callosum, anterior and posterior limb of the internal capsule, superior longitudinal fasciculus, and the centrum semiovale were analyzed with tract-based spatial statistics modified for use in neonates. Linear regression analysis was performed, and 95% confidence intervals were created for age effects on the tensor metrics with the control patients. Two-sample t-test was done to determine whether there was a difference in the tensor metrics between the normal and patient cohort. There was a statistically significant age effect on the FA and RD in the selected regions of the brain (F<0.05) and a group difference in the FA and RD between the normal and the HIE group (P<0.05). The group difference in the FA and RD between the normal and ECMO groups was seen in the anterior commissure, genu corpus callosum, right inferior longitudinal fasciculus, fronto-occipital fasciculus, centrum semiovale, and superior longitudinal fasciculus (P<0.05). Patients who were outside the 95% confidence intervals of the FA, AD, and RD overlapped with those with abnormalities clinically and on the conventional MRI. In conclusion, diffusion tensor imaging can play a significant role in detecting infants with early indications of hypoxic–ischemic brain injury.

Effects of Intrauterine Inflammation on Cortical Gray Matter of Near-Term Lambs

Introduction: Ventilation causes cerebral white matter inflammation and injury, which is exacerbated by intrauterine inflammation. However, the effects on cortical gray matter are not well-known. Our aim was to examine the effect of ventilation on the cerebral cortex of near-term lambs exposed to intrauterine inflammation. Method:Pregnant ewes at 119 ± 1 days gestation received an intra-amniotic injection of saline or lipopolysaccharide (LPS; 10 mg). Seven days later, lambs were randomized to either a high tidal volume injurious ventilation strategy (INJ_SALN = 6, INJ_LPSN = 5) or a protective ventilation strategy (PROT_SALN = 5, PROT_LPSN = 6). Respiratory parameters, heart rate and blood gases were monitored during the neonatal period. At post-mortem, the brain was collected and processed for immunohistochemical assessment. Neuronal density (NeuN), apoptotic cell death (caspase 8 and TUNEL), microglial density (Iba-1), astrocytic density (GFAP), and vascular protein extravasation (sheep serum) were assessed within the frontal, parietal, temporal and occipital lobes of the cerebral cortex. Results:A significant reduction in the number of neurons in all cortical layers except 4 was observed in LPS-exposed lambs compared to controls (layer #1: p = 0.041; layers #2 + 3: p = 0.023; layers #5 + 6: p = 0.016). LPS treatment caused a significant increase in gray matter area, indicative of edema. LPS+ventilation did not cause apoptotic cell death in the gray matter. Astrogliosis was not observed following PROT or INJ ventilation, with or without LPS exposure. LPS exposure was associated with vascular protein extravasation. Conclusion:Ventilation had little effect on gray matter inflammation and injury. Intrauterine inflammation reduced neuronal cell density, caused edema of the cortical gray matter, and blood vessel extravasation in the brain of near-term lambs.

Preterm birth and ventilation decrease surface density of glomerular capillaries in lambs, regardless of postnatal respiratory support mode

BACKGROUND

Prematurity is often complicated by respiratory support, including invasive mechanical ventilation (IMV) and noninvasive support (NIS). Compared with IMV, NIS reduces injury to the lung and brain. Prematurity may also disrupt glomerular architecture. Whether NIS differentially affects glomerular architecture is incompletely understood. We hypothesized that IMV would lead to greater disruption of glomerular architecture than NIS.

METHODS

This is a secondary analysis of kidneys from moderately preterm lambs delivered at ~131 d gestation (term ~150 d) that had antenatal steroid exposure and surfactant treatment before resuscitation by IMV. At ~3 h of age, half of the lambs were switched to NIS. Support was for 3 d or 21 d. Structural indices of glomerular architecture were quantified.

RESULTS

The number of glomerular generations was unaffected by moderate preterm birth and respiratory support, either IMV or NIS. At 3 d and 21 d of IMV or NIS, glomerular capillary surface density was not different. Glomerular capillary surface density was significantly lower in the inner and outer cortex compared with unventilated gestation age-matched or postnatal age-matched reference lambs.

CONCLUSION

Moderate preterm birth and invasive or noninvasive respiratory support decreases glomerular capillarization in the lamb kidney. This adverse effect on glomerular development may contribute to increased risk for adult-onset hypertension and renal dysfunction.

Isolated Cystic Periventricular Leukomalacia Differs from Cystic Periventricular Leukomalacia with Intraventricular Hemorrhage in Prevalence, Risk Factors and Outcomes in Preterm Infants

BACKGROUND

Cystic periventricular leukomalacia (cPVL) is the most severe white matter injury and is often associated with intraventricular hemorrhage (IVH) in preterm infants.

OBJECTIVE

The aim of this study was to investigate the prevalence, risk factors and neurodevelopmental outcomes of isolated cPVL and cPVL with low-grade and high-grade IVH in premature infants.

METHODS

From 2001 to 2012, 9,964 infants with <31 weeks' gestational age (GA) admitted to Taiwan hospitals were enrolled. cPVL was classified into three groups: isolated cPVL, cPVL with low-grade (I/II) IVH, and cPVL with high-grade (III) IVH.

RESULTS

Of 7,805 infants with complete ultrasound data, 286 (3.7%) had cPVL. Among the cPVL infants, 93 (32.5%) were isolated, 118 (41.3%) had low-grade IVH and 75 (26.2%) had high-grade IVH. The risk of cPVL with IVH was significantly higher among infants with <27 weeks' GA than those with ≥27 weeks' GA, in contrast to that of isolated cPVL. Using infants without cPVL and IVH as the reference group, the most significant predictor of isolated cPVL was neonatal sepsis (odds ratio 2.39; 95% confidence interval 1.52-3.77), while 5-min Apgar score <5 (2.50; 1.48-4.21) and prolonged mechanical ventilation (2.19; 1.42-3.42) were associated with cPVL with low-grade IVH, and GA <27 weeks (2.63; 1.56-4.42), pneumothorax (3.04; 1.40-6.65) and prolonged mechanical ventilation (3.36; 1.88-6.01) contributed to cPVL with high-grade IVH. cPVL infants with low-grade and high-grade IVH had a higher risk of abnormal neurodevelopmental outcomes than infants with isolated cPVL at the age of 24 months.

CONCLUSIONS

Isolated cPVL, cPVL with low-grade IVH and cPVL with high-grade IVH had different risk factors and neurodevelopmental outcomes, suggestive of different causal pathways.

Bronchopulmonary dysplasia: new becomes old again!

Despite the many advances in neonatology, bronchopulmonary dysplasia (BPD) continues to be a frustrating disease of prematurity. BPD is a disease which is defined oddly by its treatment rather than its pathophysiology, leading to frequently changing nomenclature which has widespread implications on our ability to both understand and follow the progression of BPD. As various treatment modalities for BPD were developed and a larger number of extremely preterm infants survived, the "old" BPD based on lung injury from oxygen therapy and mechanical ventilation transitioned into a "new" BPD focused more on the interruption of normal development. However, the interruption of normal development does not solely apply to lung development. The effects of prematurity on vascular development cannot be overstated and pulmonary vascular disease has become the new frontier of BPD. As we begin to better understand the complex, multifactorial pathophysiology of BPD, it is necessary to again focus on appropriate, pathology-driven nomenclature that can effectively describe the multiple clinical phenotypes of BPD.

Diffusion tensor imaging and histology of developing hearts

Diffusion tensor imaging (DTI) has emerged as a promising method for noninvasive quantification of myocardial microstructure. However, the origin and behavior of DTI measurements during myocardial normal development and remodeling remain poorly understood. In this work, conventional and bicompartmental DTI in addition to three-dimensional histological correlation were performed in a sheep model of myocardial development from third trimester to postnatal 5 months of age. Comparing the earliest time points in the third trimester with the postnatal 5 month group, the scalar transverse diffusivities preferentially increased in both left ventricle (LV) and right ventricle (RV): secondary eigenvalues D2 increased by 54% (LV) and 36% (RV), whereas tertiary eigenvalues D3 increased by 85% (LV) and 67% (RV). The longitudinal diffusivity D1 changes were small, which led to a decrease in fractional anisotropy by 41% (LV) and 33% (RV) in 5 month versus fetal hearts. Histological analysis suggested that myocardial development is associated with hyperplasia in the early stages of the third trimester followed by myocyte growth in the later stages up to 5 months of age (increased average myocyte width by 198%, myocyte length by 128%, and decreased nucleus density by 70% between preterm and postnatal 5 month hearts.) In a few histological samples (N = 6), correlations were observed between DTI longitudinal diffusivity and myocyte length (r = 0.86, P < 0.05), and transverse diffusivity and myocyte width (r = 0.96, P < 0.01). Linear regression analysis showed that transverse diffusivities are more affected by changes in myocyte size and nucleus density changes than longitudinal diffusivities, which is consistent with predictions of classical models of diffusion in porous media. Furthermore, primary and secondary DTI eigenvectors during development changed significantly. Collectively, the findings demonstrate a role for DTI to monitor and quantify myocardial development, and potentially cardiac disease. Copyright © 2016 John Wiley & Sons, Ltd.

Modalities of Mechanical Ventilation: Volume-Targeted Versus Pressure-Limited

BACKGROUND

Respiratory distress syndrome remains the most common admission diagnosis in the neonatal intensive care unit. Healthcare providers have a clear appreciation for the potential harm to pulmonary structures that have been associated with mechanical ventilation (MV) in the preterm infant. Although life sustaining, the goal is to optimally ventilate while limiting trauma to the neonatal lung in order to preserve long-term cardiopulmonary and neurodevelopmental outcomes.

PURPOSE

To describe, compare, and contrast 2 primary methods of neonatal MV, pressure-limited ventilation (PLV) and volume-targeted ventilation (VTV), highlighting key considerations during therapy.

METHODS

A comprehensive search of the literature was completed using the following databases: CINAHL, Cochrane, Google Scholar, and PubMed. Research articles that were published in English over the last 10 years were reviewed for key information to describe and support the topic. Expert content review was conducted prior to publication by respiratory care providers, neonatal nurse practitioners, staff nurses, and neonatologist.

FINDINGS

Technology is rapidly evolving, with the newest mechanical ventilators providing the clinician with real-time data not previously available. Advanced microprocessors and feedback mechanisms can better support various ventilatory strategies including PLV and VTV. Renewed interest in volume ventilation has led many clinicians to ask about current evidence to support ventilatory modalities with regard to timing, settings, and short- and long-term effects.

IMPLICATIONS FOR PRACTICE

The clinician understands that neonatal pulmonary status is frequently changing based on gestational age, current age, and physiologic influences. Evidence supporting recommendations for the described MV modalities of PLV and VTV is provided for both preterm and term neonates.

IMPLICATIONS FOR RESEARCH

Comparison between MV strategies, specifically PLV and VTV, including short- and long-term neurodevelopmental outcomes, is needed. Recommendations regarding physiologic tidal volume for the extremely preterm infant are lacking.

The breadth and type of systemic inflammation and the risk of adverse neurological outcomes in extremely low gestation newborns

BACKGROUND

We hypothesized that the risk of brain damage in extremely preterm neonates increases with the breadth and type of systemic inflammation, indexed by the number of elevated inflammation-related proteins and the number of functional categories of inflammation-related proteins exhibiting an elevated concentration.

METHODS

In blood from 881 infants born before 28 weeks gestation, we measured the concentrations of 25 inflammation-related proteins, representing six functional categories (cytokines, chemokines, growth factors, adhesion molecules, metalloproteinases, and liver-produced acute phase reactant proteins) on postnatal days 1, 7, and 14. We evaluated associations between the number and type of proteins whose concentrations were elevated on two separate occasions a week apart and the diagnoses of ventriculomegaly as a neonate, and at 2 years, microcephaly, impaired early cognitive functioning, cerebral palsy, and autism risk as assessed with the Modified Checklist for Autism in Toddlers screen, and in a subset of these children from 12 of 14 sites (n = 826), an attention problem identified with the Child Behavior Checklist.

RESULTS

The risk of abnormal brain structure and function overall was increased among children who had recurrent and/or persistent elevations of the 25 proteins. The risk for most outcomes did not rise until at least four proteins in at least two functional categories were elevated. When we focused our analysis on 10 proteins previously found to be associated consistently with neurological outcomes, we found the risk of low Mental Development Index on the Bayley Scales of Infant Development-II, microcephaly, and a Child Behavior Checklist-defined attention problem increased with higher numbers of these recurrently and/or persistently elevated proteins.

INTERPRETATION

Increasing breadth of early neonatal inflammation, indexed by the number of protein elevations or the number of protein functional classes elevated, is associated with increasing risk of disorders of brain structure and function among infants born extremely preterm.

Impaired visual fixation at the age of 2 years in children born before the twenty-eighth week of gestation. Antecedents and correlates in the multicenter ELGAN study

BACKGROUND

Very little is known about the prevalence, antecedents, and correlates of impaired visual fixation in former very preterm newborns.

METHODS

In the multicenter ELGAN study sample of 1057 infants born before the twenty-eighth week of gestation who had a developmental assessment at 2 years corrected age, we identified 73 who were unable to follow an object across the midline. We compared them to the 984 infants who could follow an object across the midline.

RESULTS

In this sample of very preterm newborns, those who had impaired visual fixation were much more likely than those without impaired visual fixation to have been born after the shortest of gestations (odds ratio, 3.2; 99% confidence interval, 1.4-7.5) and exposed to maternal aspirin (odds ratio, 5.2; 99% confidence interval, 2.2-12). They were also more likely than their peers to have had prethreshold retinopathy of prematurity (odds ratio, 4.1; 99% confidence interval, 1.8-9.0). At age 2 years, the children with impaired fixation were more likely than others to be unable to walk (even with assistance) (odds ratio, 7.5; 99% confidence interval, 2.2-26) and have a Mental Development Index more than three standard deviations below the mean of a normative sample (odds ratio, 3.6; 99% confidence interval, 1.4-8.2).

CONCLUSION

Risk factors for brain and retinal damages, such as very low gestational age, appear to be risk factors for impaired visual fixation. This inference is further supported by the co-occurrence at age 2 years of impaired visual fixation, inability to walk, and a very low Mental Development Index.

Respiratory support for premature neonates in the delivery room: effects on cardiovascular function and the development of brain injury

The transition to newborn life in preterm infants is complicated by immature cardiovascular and respiratory systems. Consequently, preterm infants often require respiratory support immediately after birth. Although aeration of the lung underpins the circulatory transition at birth, positive pressure ventilation can adversely affect cardiorespiratory function during this vulnerable period, reducing pulmonary blood flow and left ventricular output. Furthermore, pulmonary volutrauma is known to initiate pulmonary inflammatory responses, resulting in remote systemic involvement. This review focuses on the downstream consequences of positive pressure ventilation, in particular, interactions between cardiovascular output and the initiation of a systemic inflammatory cascade, on the immature brain. Recent studies have highlighted that positive pressure ventilation strategies are precursors of cerebral injury, probably mediated through cerebral blood flow instability. The presence of, or initiation of, an inflammatory cascade accentuates adverse cerebral blood flow, in addition to being a direct source of brain injury. Importantly, the degree of brain injury is dependent on the nature of the initial ventilation strategy used.