Hypocarbia in preterm infants with periventricular leukomalacia: the relation between hypocarbia and mechanical ventilation

Oxygen saturation levels and retinopathy of prematurity in extremely preterm infants - a case control study

PURPOSE

To investigate the association of risk factors, including oxygen exposure, for developing retinopathy of prematurity (ROP) in preterm infants at increased risk of ROP.

METHODS

A case-control study was conducted where each infant born at < 28 weeks gestation with ROP was matched with another without ROP over five years (July 2015 - June 2020). Clinical information about the infants was collected from electronic medical records, including method of oxygen delivery, oxygen saturation (SpO2), fraction of inspired oxygen (FiO2) and mean airway pressure (MAP) measurements. MATLAB was used for a time-averaged analysis. Stata/SE 16.0 was used for statistical analysis.

RESULTS

123 ROP/non-ROP pairs were included in this study. The time-averaged SpO2 analysis showed non-ROP group spent more time in hyperoxia than the ROP group (p < 0.001). The non-ROP group had lower respiratory severity scores and analysis when FiO2 > 21% showed that were was no difference in SpO2 between the two groups when the infants were receiving oxygen support. Conditional logistic regressions showed neonatal surgery significantly increased the risk of ROP (OR = 1.4347, p = 0.010), while the influence of birthweight (odds ratio of 0.9965, p = 0.001) and oxygen exposure (OR = 0.9983, p = 0.012) on ROP outcome was found to be negligible as their odds ratios indicated no influence.

CONCLUSIONS

At times when infants were receiving respiratory support (FiO2 > 21%) the SpO2 data indicated no difference in SpO2 between the ROP and non-ROP groups. Analysis of clinical variables found that neonatal surgery increased the odds of developing ROP.

Capnometry during neonatal transport-Mini review

AIM

The aim of this review was to give an overview of available data on end-tidal CO2 (etCO2 ) monitoring, also called capnometry, during neonatal transport.

METHODS

Pubmed/MEDLINE database was searched using research question (capno* OR etCO2 OR detCO2 OR (['end tidal' OR 'end-tidal'] AND [CO2 OR 'carbon dioxide']) AND (neonat* OR infant* OR newborn*) AND transport*). All articles relevant to the topic were reviewed and summarised.

RESULTS

The lack of studies relevant to neonatal transport prompted us to extend the search to capnometry in a neonatal intensive care setting. The published studies are showing conflicting results. The different study populations, technologies used to measure etCO2 , types of etCO2 sampling and the diverse sites of blood gas tests make the data unsuitable for systematic comparison.

CONCLUSION

Further research to obtain more data on capnometry during neonatal transport will be necessary to define precisely under what circumstances can end-tidal monitoring of CO2 be reliably used in neonates during transport and also how to interpret the measured values.

Closed-Loop Control of Arterial CO2 in Mechanical Ventilation of Neonates

During mechanical ventilation of the neonate the main goal is to stabilize respiratory function of the often premature lungs. Ventilating the patient without inflicting harm is then the subordinated next goal. Ideally the arterial partial pressure of CO₂ lays within a normocapnic range and fluctuations are kept minimal. By closely monitoring CO₂ and controlling ventilation parameters accordingly, CO₂ levels in the blood can be managed. We present an approach consisting of a cascaded controller for arterial CO₂ by approximating arterial partial pressure PaCO₂ from end-tidal PetCO₂. As a proof of concept, feasibility of the controller was first evaluated on a mathematical patient model and subsequently in-vivo in lamb experiments. The controller is able to regulate CO₂ into a normocapnic range in both setups with satisfactory stationarity within the target range. Estimation of the arterial partial pressure of CO₂ remains a critical aspect that needs to be further investigated. Clinical relevance-Closed-loop control of CO2 in mechanical ventilation aims to avoid PaC O2 extremes and to reduce fluctuations. Both are a relevant risk factors especially for neurological complications among preterm newborns.

Hypocapnia in early hours of life is associated with brain injury in moderate to severe neonatal encephalopathy

OBJECTIVE

To evaluate the association between hypocapnia within the first 24 h of life and brain injury assessed by a detailed MRI scoring system in infants receiving therapeutic hypothermia (TH) for neonatal encephalopathy (NE) stratified by the stage of NE.

STUDY DESIGN

This retrospective cohort study included infants who received TH for mild to severe NE.

RESULTS

188 infants were included in the study with 48% having mild and 52% moderate-severe NE. Infants with moderate-severe NE spent more time in hypocapnia (PCO₂ ≤ 35 mmHg) and presented with more severe brain injury on MRI compared to mild cases. The MRI injury score increased by 6% for each extra hour spent in hypocapnic range in infants with moderate-severe NE. There was no association between hypocapnia and injury scores in mild cases.

CONCLUSION

In infants with moderate-severe NE, the hours spent in hypocapnia was an independent predictor of brain injury.

End-tidal capnography monitoring in infants ventilated on the neonatal intensive care unit

OBJECTIVE

To assess whether end-tidal capnography (EtCO2) monitoring reduced the magnitude of difference in carbon dioxide (CO2) levels and the number of blood gases in ventilated infants.

STUDY DESIGN

A case-control study of a prospective cohort (n = 36) with capnography monitoring and matched historical controls (n = 36).

RESULT

The infants had a median gestational age of 31.6 weeks. A reduction in the highest CO2 level on day 1 after birth was observed after the introduction of EtCO2 monitoring (p = 0.043). There was also a reduction in the magnitude of difference in CO2 levels on days 1 (p = 0.002) and 4 (p = 0.049) after birth. There was no significant difference in the number of blood gases.

CONCLUSION

Continuous end-tidal capnography monitoring in ventilated infants was associated with a reduction in the degree of the magnitude of difference in CO2 levels and highest level of CO2 on the first day after birth.

Temporal inversion of the acid-base equilibrium in newborns: an observational study

Background

A considerable fraction of newborn infants experience hypoxia-ischaemia and metabolic acidosis at birth. However, little is known regarding the biological response of newborn infants to the pH drift from the physiological equilibrium. The aim of this study was to investigate the relationship between the pH drift at birth and postnatal acid-base regulation in newborn infants.

Methods

Clinical information of 200 spontaneously breathing newborn infants hospitalised at a neonatal intensive care centre were reviewed. Clinical variables associated with venous blood pH on days 5-7 were assessed.

Results

The higher blood pH on days 5-7 were explained by lower cord blood pH (-0.131, -0.210 to -0.052; regression coefficient, 95% confidence interval), greater gestational age (0.004, 0.002 to 0.005) and lower partial pressure of carbon dioxide on days 5-7 (-0.005, -0.006 to -0.004) (adjusted for sex, postnatal age and lactate on days 5-7).

Conclusion

In relatively stable newborn infants, blood pH drift from the physiological equilibrium at birth might trigger a system, which reverts and over-corrects blood pH within the first week of life. Given that the infants within the study cohort was spontaneously breathing, the observed phenomenon might be a common reaction of newborn infants to pH changes at birth.

Spontaneous hypocarbia without mechanical ventilation in preterm infants with cystic periventricular leukomalacia

AIM

Hypocarbia induced by mechanical ventilation has been considered a main cause of cystic periventricular leukomalacia (cPVL). However, hypocarbia may occur spontaneously in response to intracellular metabolic acidosis. We aimed to assess whether hypocarbia is more common during mechanical respiratory support than during spontaneous ventilation in infants with cPVL.

METHOD

In this single-centre, retrospective chart analysis, we compared partial pressure of carbon dioxide (pCO₂ ) during the first 96 hours of life in infants with cPVL during endotracheal mechanical ventilation, non-invasive respiratory support, or without respiratory support.

RESULTS

Cystic periventricular leukomalacia was diagnosed in 23 infants born between 2006 and 2017. Gestational age was 24 weeks in two infants and ranged between 28 and 32 weeks in 21 infants. In these 21 infants, pCO₂ less than 35 mm Hg during the first 96 ours of life accounted for 9/60 (15%) measurements during endotracheal mechanical ventilation, 16/116 (14%) during non-invasive respiratory support and 14/42 (33%) in infants without respiratory support (P = .014).

CONCLUSION

In our series of infants with cPVL, hypocarbia was more common without respiratory support than during endotracheal mechanical ventilation and non-invasive respiratory support. This would suggest that hypocarbia is a symptom rather than a cause of cPVL in these infants.

Assessment of sidestream end-tidal capnography in ventilated infants on the neonatal unit

OBJECTIVES

Continuous monitoring of carbon dioxide (CO₂ ) levels can be achieved by capnography. Our aims were to compare the performance of a sidestream capnograph with a low dead space and sampling rate to a mainstream device and evaluate whether its results correlated with arterial/capillary CO₂ levels in infants with different respiratory disease severities.

WORKING HYPOTHESES

End-tidal carbon dioxide (EtCO₂ ) results by sidestream and mainstream capnography would correlate, but the divergence of EtCO₂ and CO₂ results would occur in more severe lung disease.

STUDY DESIGN

Prospective cohort study.

PATIENT-SUBJECT SELECTION

Fifty infants with a median (interquartile range) gestational age of 31.1 (27.1-37.4) weeks and birth weight of 1.37 (0.76-2.95) kg.

METHODOLOGY

Concurrent measurements of EtCO₂ in ventilated infants were made using a new Microstream sidestream device and a mainstream capnograph (gold standard). Results from both devices were compared with arterial or capillary CO₂ levels. The ratio of dead space to tidal volume (Vd/Vt) was calculated to assess respiratory disease severity.

RESULTS

The mean difference between the concurrent measurements of EtCO₂ was -0.54 ± 0.67 kPa (95% agreement levels - 1.86 to 0.77 kPa), the correlation between the two was r = .85 (P < .001). Sidestream capnography results correlated better with partial pressure of CO₂ (PCO₂ ) levels in infants with less (Vd/Vt < 0.35; r²  = .66, P < .001) rather than more severe (Vd/Vt > 0.35; r²  = .33, P = .01) lung disease.

CONCLUSIONS

The sidestream capnography performed similarly to the mainstream capnography. The poorer correlation of EtCO₂ to PCO₂ levels in infants with severe respiratory disease should highlight to clinicians increased ventilation-perfusion mismatch.

Effect of high-frequency oscillatory ventilation combined with volume guarantee on preterm infants with hypoxic respiratory failure

BACKGROUND

The aim of this study was to assess the effect of volume guarantee (VG) on high-frequency oscillatory ventilation (HFOV) compared with HFOV alone in preterm infants with hypoxic respiratory failure (HRF).

METHODS

Fifty-two preterm infants with HRF refractory to conventional mechanical ventilation (CMV) were enrolled in this study. Between June 2012 and February 2016, HFOV alone was used as rescue therapy when CMV failed for 34 infants, whereas HFOV combined with VG was used as rescue therapy for the other 18 infants between March 2016 and December 2017.

RESULTS

HFOV combined with VG resulted in a reduction in the combined outcome of death or bronchopulmonary dysplasia (BPD) (p = 0.017) and also a reduction in episodes of hypercarbia (p = 0.010) compared with HFOV alone.

CONCLUSION

In this study, the preterm infants with HRF ventilated using HFOV combined with VG had a reduced combined outcome of death or BPD and hypercarbia compared with those who received HFOV alone.

Volume-targeted versus pressure-limited ventilation for preterm infants

BACKGROUND

To compare the effects of volume-targeted ventilation (VTV) with pressure-limited ventilation (PLV) in preterm infants.

METHODS

A total of 100 preterm infants who required mechanical ventilation during the two study periods were investigated. PLV was used for 50 preterm infants during period 1 and VTV was used for 50 preterm infants during period 2. Clinical outcomes including mortality rate, duration of mechanical ventilation, air leak syndrome, hypocarbia, hypercarbia, hypoxemia, combined outcome of death or bronchopulmonary dysplasia (BPD), intraventricular hemorrhage, and retinopathy of prematurity were evaluated.

RESULTS

There was no significant difference (p > 0.05) in the duration of mechanical ventilation, air leak syndrome, hypocarbia, hypoxemia, or BPD between the two study groups. The mortality rate, hypercarbia, and combined outcome of death or BPD were significantly lower (p < 0.05) in the VTV group compared with the PLV group.

CONCLUSION

Preterm infants using VTV had a lower mortality rate, less hypercarbia, and a significant decrease in the combined outcome of death or BPD.

The complex aetiology of cerebral palsy

Cerebral palsy (CP) is the most prevalent, severe and costly motor disability of childhood. Consequently, CP is a public health priority for prevention, but its aetiology has proved complex. In this Review, we summarize the evidence for a decline in the birth prevalence of CP in some high-income nations, describe the epidemiological evidence for risk factors, such as preterm delivery and fetal growth restriction, genetics, pregnancy infection and other exposures, and discuss the success achieved so far in prevention through the use of magnesium sulfate in preterm labour and therapeutic hypothermia for birth-asphyxiated infants. We also consider the complexities of disentangling prenatal and perinatal influences, and of establishing subtypes of the disorder, with a view to accelerating the translation of evidence into the development of strategies for the prevention of CP.

The role of near-infrared spectroscopy monitoring in preterm infants

Neurological morbidities such as peri/intraventricular hemorrhage and periventricular leukomalacia largely determine the neurodevelopmental outcome of vulnerable preterm infants and our aim should be to minimize their occurrence or severity. Bed-side neuromonitoring could provide valuable pieces of information about possible hemodynamic disturbances that are significantly associated with neurological morbidities and increased mortality. Near-infrared spectroscopy offers evaluation of regional cerebral oxygenation, which in conjunction with other non-invasive methods may give us a more complete picture about end-organ perfusion. This monitoring tool could help us fully understand the pathophysiology of severe neurological morbidities and guide our management in order to reduce their incidence.

Case-control study demonstrates that surfactant without intubation delayed mechanical ventilation in preterm infants

AIM

This Norwegian study explored whether administering surfactant without intubation (SWI) delayed the need for early mechanical ventilation and reduced respiratory and nonrespiratory complications in infants born before 32 weeks of gestational age.

METHODS

We compared 262 infants admitted to a level-three neonatal intensive care unit: 134 born before the introduction of SWI on 1 December 2011 were in the control group and 128 infants born after this date were in the study group.

RESULTS

The proportion of infants treated with surfactant did not differ between the groups, but mechanical ventilation before 72 hours of life was lower in the study group than the control group, with an odds ratio (OR) of 0.58 and a 95% confidence interval (CI) of 0.35-0.96. Fewer study group infants needed supplemental oxygen at 28 days of life. One study infant and nine control infants had intraventricular haemorrhage grades 3-4 and, or, cystic periventricular leukomalacia (OR 0.10, 95% CI 0.01-0.83). These results were strengthened in analyses restricted to surfactant-treated infants and the proportion needing supplemental oxygen at 36 weeks was reduced.

CONCLUSION

Surfactant without intubation reduced the need for early mechanical ventilation and major brain injuries in infants born at <32 weeks of gestation.

Relationship between PCO2 and unfavorable outcome in infants with moderate-to-severe hypoxic ischemic encephalopathy

BACKGROUND

Abnormal PCO2 is common in infants with hypoxic ischemic encephalopathy (HIE). The objective was to determine whether hypocapnia was independently associated with unfavorable outcome (death or severe neurodevelopmental disability at 18 mo) in infants with moderate-to-severe HIE.

METHODS

This was a post hoc analysis of the CoolCap Study in which infants were randomized to head cooling or standard care. Blood gases were measured at prespecified times after randomization. PCO2 and follow-up data were available for 196 of 234 infants. Analyses were performed to investigate the relationship between hypocapnia in the first 72 h after randomization and unfavorable outcome.

RESULTS

After adjusting for pH, amplitude-integrated electroencephalogram background and seizures, birth weight, Apgar score at 5 min, cooling status, and Sarnat stage, PCO2 was inversely associated with unfavorable outcome (P < 0.001). The probability of unfavorable outcome was 0.20 ± 0.1 (point estimate ± SE), 0.53 ± 0.23 and 0.89 ± 0.16 for a PCO2 of 40, 30, and 20 mm Hg respectively and was greater in infants with severe HIE than with moderate HIE.

CONCLUSIONS

Hypocapnia in infants with moderate-to-severe HIE was independently associated with unfavorable outcome. Future studies of controlled normocapnia will be important.

Effects of permissive hypercapnia on pulmonary and neurodevelopmental sequelae in extremely low birth weight infants: a meta-analysis

Objectives

To perform a systematic review and meta-analysis of the efficacy and safety of permissive hypercapnia in extremely low birth weight infants.

Methods

A systematic search of MEDLINE, EMBASE, the Cochrane Database of randomized trials. Eligibility and quality of trials were assessed, and data on study design, patient characteristics, and relevant outcomes were extracted.

Results

Four studies that enrolled a total of 693 participants were selected. Meta-analysis revealed no effect of permissive hypercapnia on decreasing rates of bronchopulmonary dysplasia (BPD). Permissive hypercapnia also had no significant effect on mortality, intraventricular haemorrhage (IVH), IVH (grade 3–4), periventricular leukomalacia (PVL), necrotising enterocolitis (NEC), retinopathy of prematurity (ROP) or air leaks in extremely low birth weight infants. Neurodevelopmental outcomes were comparable at 18–22 months’ corrected age in two studies. permissive hypercapnia did not increase the risk of cerebral palsy, Mental Developmental Index <70, Psychomotor Developmental Index <70, visual deficit, or hearing deficit.

Conclusions

Permissive hypercapnia did not reduce the rate of BPD in extremely low birth weight infants. The rates of mortality, IVH, PVL, NEC, ROP and neurodevelopmental outcomes did not differ between these two groups. These results suggest that permissive hypercapnia does not bring extra benefits in extremely low birth weight infants.

Cardiorespiratory events in preterm infants: etiology and monitoring technologies

Every year, an estimated 15 million infants are born prematurely (<37 weeks gestation) with premature birth rates ranging from 5 to 18% across 184 countries. Although there are a multitude of reasons for this high rate of preterm birth, once birth occurs, a major challenge of infant care includes the stabilization of respiration and oxygenation. Clinical care of this vulnerable infant population continues to improve, yet there are major areas that have yet to be resolved including the identification of optimal respiratory support modalities and oxygen saturation targets, and reduction of associated short- and long-term morbidities. As intermittent hypoxemia is a consequence of immature respiratory control and resultant apnea superimposed upon an immature lung, improvements in clinical care must include a thorough knowledge of premature lung development and pathophysiology that is unique to premature birth. In Part 1 of a two-part review, we summarize early lung development and diagnostic methods for cardiorespiratory monitoring.

Increased fetal heart rate variability in periventricular leukomalacia

OBJECTIVE

This study used quantitative analysis to determine whether increased variability in fetal heart rate (FHR) is related to the risk of developing periventricular leukomalacia (PVL).

METHODS

We analyzed 124 FHR traces of neonates delivered preterm at 27-33 weeks' gestation to 105 mothers. FHR traces 1-3h before delivery were translated into power-spectrum curves using a fast Fourier transformation. The total power (the area under the curve of 1-10 cycles per minute), segmental power of every cycle per minute, peak power, and frequency edges were calculated, and their relationship with the subsequent development of PVL was examined.

RESULTS

Total power was significantly higher in the PVL group (n=9, median 1813, range 1064-2426) compared to the non-PVL group (n=114, median 1383, range 381-3324, p=0.029). Infants in the PVL group had greater segmental power in segments with 1-2, 2-3, and 9-10 cycles per minute, than those in the non-PVL group. Total power of ⩾1550 was significantly correlated with the subsequent development of PVL and premature rupture of membranes. Furthermore, the frequency of pregnancy-induced hypertension was significantly reduced in the fetuses with a total power of ⩾1550.

CONCLUSION

Our study suggests that a fetus with increased FHR variability is at risk of developing PVL. This study provides additional evidence supporting the contribution of antenatal factors to the subsequent development of PVL.

White Matter Injury in Premature Newborns

Preterm newborns are highly susceptible to brain injury. White matter injury is among the dominant patterns of brain injury in preterm newborns. the purpose of this review is to discuss the pathogenesis, diagnosis, management, and prevention of white matter injury in premature newborns. the long-term outcome of white matter injury in children born prematurely is also addressed.

Setting the Ventilator in the NICU

Success in providing respiratory support to the neonate requires a clear understanding of the context in which it is being applied. Perhaps more than for any other age group, the array of different situations in which ventilation is applied to the newborn infant is extremely broad, with in each case different pathophysiological disturbances and often the need to use a specific approach to apply ventilation optimally. Table 42.1 provides a list of the more common situations in which conventional ventilation is used in the neonate and includes some considerations regarding ventilator settings for each situation. For each situation, a suggested mode of ventilation is indicated, along with target ranges for positive end-expiratory pressure (PEEP) and tidal volume (V_T). Further discussion of the physiological rationale and available evidence for ventilator settings is set out below.

Could cord blood cell therapy reduce preterm brain injury?

Major advances in neonatal care have led to significant improvements in survival rates for preterm infants, but this occurs at a cost, with a strong causal link between preterm birth and neurological deficits, including cerebral palsy (CP). Indeed, in high-income countries, up to 50% of children with CP were born preterm. The pathways that link preterm birth and brain injury are complex and multifactorial, but it is clear that preterm birth is strongly associated with damage to the white matter of the developing brain. Nearly 90% of preterm infants who later develop spastic CP have evidence of periventricular white matter injury. There are currently no treatments targeted at protecting the immature preterm brain. Umbilical cord blood (UCB) contains a diverse mix of stem and progenitor cells, and is a particularly promising source of cells for clinical applications, due to ethical and practical advantages over other potential therapeutic cell types. Recent studies have documented the potential benefits of UCB cells in reducing brain injury, particularly in rodent models of term neonatal hypoxia–ischemia. These studies indicate that UCB cells act via anti-inflammatory and immuno-modulatory effects, and release neurotrophic growth factors to support the damaged and surrounding brain tissue. The etiology of brain injury in preterm-born infants is less well understood than in term infants, but likely results from episodes of hypoperfusion, hypoxia–ischemia, and/or inflammation over a developmental period of white matter vulnerability. This review will explore current knowledge about the neuroprotective actions of UCB cells and their potential to ameliorate preterm brain injury through neonatal cell administration. We will also discuss the characteristics of UCB-derived from preterm and term infants for use in clinical applications.

Diffusion tensor imaging in extremely low birth weight infants managed with hypercapnic vs. normocapnic ventilation

BACKGROUND

Permissive hypercapnia is a ventilatory strategy used to prevent lung injury in ventilated extremely low birth weight (ELBW, birth weight ≤1,000 g) infants. However, there is retrospective evidence showing that high CO2 is associated with brain injury.

OBJECTIVE

The objective of this study was to compare brain white matter development at term-equivalent age in ELBW infants randomized to hypercapnic vs. normocapnic ventilation during the first week of life and in healthy non-ventilated term newborns.

MATERIALS AND METHODS

Twenty-two ELBW infants from a randomized controlled trial were included in this study; 11 received hypercapnic (transcutaneous PCO2 [tcPCO2] 50-60 mmHg) ventilation and 11 normocapnic (tcPCO2 35-45 mmHg) ventilation during the first week of life while still intubated. In addition, ten term healthy newborns served as controls. Magnetic resonance imaging (MRI) with diffusion tensor imaging (DTI) was performed at term-equivalent age for the ELBW infants and at approximately 2 weeks of age for the control infants. White matter injury on conventional MRI was graded in the ELBW and control infants using a scoring system adopted from literature. Tract-based spatial statistics (TBSS) was used to evaluate for differences in DTI measured fractional anisotropy (FA, spatially normalized to a customized template) among the ELBW and term control infants.

RESULTS

Conventional MRI white matter scores were not different (7.3 ± 1.7 vs. 6.9 ± 1.4, P = 0.65) between the hypercapnic and normocapnic ELBW infants. TBSS analysis did not show significant differences (P < 0.05, corrected) between the two ELBW infant groups, although before multiple comparisons correction, hypercapnic infants had many regions with lower FA and no regions with higher FA (P < 0.05, uncorrected) compared to normocapnic infants. When compared to the control infants, normocapnic ELBW infants had a few small regions with significantly lower FA, while hypercapnic ELBW infants had more widespread regions with significantly lower FA (P < 0.05, fully corrected for multiple comparisons).

CONCLUSIONS

Normocapnic ventilation vs. permissive hypercapnia may be associated with improved white matter development at term-equivalent age in ELBW infants. This effect, however, was small and was not apparent on conventional MRI. Further research is needed using larger sample sizes to assess if permissive hypercapnic ventilation in ELBW infants is associated with worse white matter development.

Closed-form fiducial confidence intervals for some functions of independent binomial parameters with comparisons

Approximate closed-form confidence intervals (CIs) for estimating the difference, relative risk, odds ratio, and linear combination of proportions are proposed. These CIs are developed using the fiducial approach and the modified normal-based approximation to the percentiles of a linear combination of independent random variables. These confidence intervals are easy to calculate as the computation requires only the percentiles of beta distributions. The proposed confidence intervals are compared with the popular score confidence intervals with respect to coverage probabilities and expected widths. Comparison studies indicate that the proposed confidence intervals are comparable with the corresponding score confidence intervals, and better in some cases, for all the problems considered. The methods are illustrated using several examples.

Different gestational ages and changing vulnerability of the premature brain

In recent decades, there has been a general increase in survival rates of preterm and low birth weight infants, but this overall decrease in perinatal mortality has not been accompanied by a decrease in long-term physical and mental disability. In order to reduce the long-term sequelae of prematurity and to establish preventive measures, it is important to identify risk factors since the main determinant of specific vulnerability to different types of lesions is gestational age. The regional tissue vulnerability at a given gestational age is probably determined by the local metabolic requirements together with specific cell characteristics and their level of maturation. In this article, we discuss the most common neonatal cerebral lesions (cerebellar haemorrhage, germinal matrix intraventricular haemorrhage, periventricular leukomalacia, arterial ischaemic stroke, cerebral vein sinus thrombosis and hypoxic-ischaemic encephalopathy) related to the gestational age-dependent vulnerability of the premature brain.

Incidence of hypo- and hyper-capnia in a cross-sectional European cohort of ventilated newborn infants

OBJECTIVE

To determine the incidence of hypo- and hyper-capnia in a European cohort of ventilated newborn infants.

DESIGN AND SETTING

Two-point cross-sectional prospective study in 173 European neonatal intensive care units.

PATIENTS AND METHODS

Patient characteristics, ventilator settings and measurements, and blood gas analyses were collected for endotracheally ventilated newborn infants on two separate dates.

RESULTS

A total of 1569 blood gas analyses were performed in 508 included patients with a mean±SD Pco2 of 48±12 mm Hg or 6.4±1.6 kPa (range 17-104 mm Hg or 2.3-13.9 kPa). Hypocapnia (Pco2<30 mm Hg or 4 kPa) and hypercapnia (Pco2>52 mm Hg or 7 kPa) was present in, respectively, 69 (4%) and 492 (31%) of the blood gases. Hypocapnia was most common in the first 3 days of life (7.3%) and hypercapnia after the first week of life (42.6%). Pco2 was significantly higher in preterm infants (49 mm Hg or 6.5 kPa) than term infants (43 mm Hg or 5.7 kPa) and significantly lower during pressure-limited ventilation (47 mm Hg or 6.3±1.6 kPa) compared with volume-targeted ventilation (51 mm Hg or 6.8±1.7 kPa) and high-frequency ventilation (50 mm Hg or 6.7±1.7 kPa).

CONCLUSIONS

This study shows that hypocapnia is a relatively uncommon finding during neonatal ventilation. The higher incidence of hypercapnia may suggest that permissive hypercapnia has found its way into daily clinical practice.

Apnea of prematurity--perfect storm

With increased survival of preterm infants as young as 23 weeks gestation, maintaining adequate respiration and corresponding oxygenation represents a clinical challenge in this unique patient cohort. Respiratory instability characterized by apnea and periodic breathing occurs in premature infants because of immature development of the respiratory network. While short respiratory pauses and apnea may be of minimal consequence if oxygenation is maintained, they can be problematic if accompanied by chronic intermittent hypoxemia. Underdevelopment of the lung and the resultant lung injury that occurs in this population concurrent with respiratory instability creates the perfect storm leading to frequent episodes of profound and recurrent hypoxemia. Chronic intermittent hypoxemia contributes to the immediate and long term co-morbidities that occur in this population. In this review we discuss the pathophysiology leading to the perfect storm, diagnostic assessment of breathing instability in this unique population and therapeutic interventions that aim to stabilize breathing without contributing to tissue injury.

Sidestream microstream end tidal carbon dioxide measurements and blood gas correlations in neonatal intensive care unit

OBJECTIVE

The study was designed to assess the use of newer sidestream microstream end tidal carbon dioxide (ETCO(2) ) device in predicting blood carbon dioxide (PCO(2) ) measurements in very low birth weight (VLBW = birth weight <1,500 g) and non-VLBW NICU neonates.

STUDY DESIGN

Sidestream microstream ETCO(2) detectors were allowed time to calibrate and reach steady state prior to blood gas measurements. Blood CO(2) (PCO(2) ) and simultaneous ETCO(2) were recorded. Ratio of dead space to tidal volume (VD/VT) was calculated using modified Bohr's equation. Correlation coefficient, estimates of difference, standard deviation, and 95% limits of agreement between ETCO(2) and PCO(2) concentrations were calculated.

RESULTS

Two hundred eighty-six paired samples were collected from 48 ventilated NICU patients. Average PCO(2) and ETCO(2) were 58.4 and 50.6 with a correlation of 0.76. Subgroup analysis showed a correlation of 0.73 in 204 paired blood from 34 VLBW infants and 0.82 in 82 paired samples from non-VLBW infants. Estimates of difference ± standard deviation between PCO(2) and ETCO(2) concentrations in these three groups, respectively (ALL, VLBW, and non-VLBW) were 7.84 ± 9.96, 8.2 ± 10.16, and 6.95 ± 9.45. The correlation coefficient significantly improved in the VLBW group to 0.86 with dead space to tidal volume ratio (VD/VT) <30% (0.86 vs. 0.42; P < 0.001).

CONCLUSION

ETCO(2) measurements using sidestream microstream technology in VLBW demonstrated that the correlation of ETCO(2) and PCO(2) was moderate, but the agreement was less than adequate (bias > 5 mmHg in all groups). The results improved with lower VD/VT, suggesting that sidestream capnography is more reliable in conditions of less severe lung disease.

Less invasive surfactant administration in extremely preterm infants: impact on mortality and morbidity

BACKGROUND

A new mode of surfactant administration without intubation - less invasive surfactant administration (LISA) - has recently been described for premature infants.

OBJECTIVE

We report single-center outcome data of extremely premature infants who have been managed by LISA in our department. Mortality and morbidity rates of the cohort were compared to historical controls from our own center and to data of the Vermont-Oxford Neonatal Network (VONN).

PATIENTS AND METHODS

All infants born at 23-27 weeks' gestational age during 01/2009 and 06/2011 (n = 224) were managed by LISA and included in the study group.

RESULTS

LISA was tolerated by 94% of all infants. 68% of infants stayed on continuous positive airway pressure on day 3. The rate of mechanical ventilation was 35% within the first week and 59% during the entire hospital stay. Compared to historical controls, we found significantly higher survival rates (75.8 vs. 64.1%) and significantly less intraventricular hemorrhage (IVH) (28.1 vs. 45.9%), severe IVH (13.1 vs. 23.9%) and cystic periventricular leukomalacia (1.2 vs. 5.6%); only persistent ductus arteriousus (PDA) (74.7 vs. 52.6%) and retinopathy of prematurity (ROP) (40.5 vs. 21.1%) occurred significantly more often. Compared to VONN data, we found significantly less chronic lung disease (20.6 vs. 46.4%), severe cerebral lesions (IVH 3/4 + cystic PVL; 9.4 vs. 16.1%) and ROP (all grades) (40.5 vs. 56.5%); only PDA (74.7 vs. 63.1%) and severe ROP (> grade 2) (24.1 vs. 14.1%) occurred significantly more often in our cohort.

CONCLUSION

Surfactant can be effectively and safely delivered via LISA and this is associated with low rates of mechanical ventilation and various adverse outcomes in extremely premature infants.

Cerebral white matter and neurodevelopment of preterm infants after coagulase-negative staphylococcal sepsis

OBJECTIVE

Coagulase-negative staphylococci are the most common pathogens causing late-onset sepsis in the neonatal intensive care unit. Neonatal sepsis can be associated with cerebral white matter damage in preterm infants. Neurodevelopment has been shown to be correlated with apparent diffusion coefficients, fractional anisotropy, and axial and radial diffusivities of the white matter.

DESIGN

Prospective cohort study.

SETTING

Twenty-eight-bed neonatal intensive care unit at a tertiary care children's hospital.

PATIENTS

Seventy preterm infants (gestational age <32 wks), 28 with coagulase-negative staphylococcal sepsis (group 1) and 42 without sepsis (group 2).

INTERVENTION

The values of apparent diffusion coefficients, fractional anisotropy, and axial and radial diffusivity of three white matter regions (parietal, frontal, and occipital), estimated with diffusion-tensor magnetic resonance imaging with a 3.0-T magnetic resonance imaging system, were obtained at term-equivalent age. Neurodevelopmental outcome assessments were performed at 15 months (Griffiths Mental Developmental Scales) and 24 months (Bayley Scales of Infant and Toddler Development, Third Edition) corrected age.

MEASUREMENTS AND MAIN RESULTS

Values of apparent diffusion coefficients, fractional anisotropy, and axial and radial diffusivity of the left and right white matter regions were equal in all patients. There was no significant difference in apparent diffusion coefficient values (mean of total: 1.593 ± 0.090 × 10mm(-3)/sec(2) and 1.601 ± 0.117 × 10mm(-3)/sec(2), respectively, p = .684), fractional anisotropy values (mean of total: 0.19 ± 0.04 and 0.19 ± 0.03, respectively, p = .350), radial diffusivity (mean of total: 1.420 ± 0.09 × 10mm(-3)/sec(2)and 1.425 ± 0.12 × 10mm(-3)/sec(2), respectively, p = .719), and axial diffusivity (mean of total: 1.940 ± 0.12 × 10mm(-3)/sec(2) and 1.954 ± 0.13 × 10mm(-3)/sec(2), respectively, p = .590) in the three combined regions between the two groups. No significant differences were found in neurodevelopmental outcome at 24 months.

CONCLUSIONS

No association was found between coagulase-negative staphylococcal sepsis in preterm infants and cerebral white matter damage as determined by values of apparent diffusion coefficients, fractional anisotropy, and radial and axial diffusivity at term-equivalent age, and no adverse effect was seen on early neurodevelopmental outcome.

Maternal carbon dioxide level during labor and its possible effect on fetal cerebral oxygenation: mini review

During pregnancy, and especially during labor, the maternal carbon dioxide level declines considerably. Maternal carbon dioxide levels show a close relation with fetal carbon dioxide levels. The latter affects fetal cerebral oxygenation by regulating cerebral blood flow and shifting the oxyhemoglobin dissociation curve. In addition, maternal hypocapnia appears to impair placental oxygen transfer. Thus, maternal hyperventilation may interfere with optimal fetal cerebral oxygenation. Here, we provide a brief overview of the literature relevant to this issue.

End-tidal carbon dioxide monitoring in very low birth weight infants: correlation and agreement with arterial carbon dioxide

OBJECTIVE

We aimed to determine the correlation and the agreement between end-tidal carbon dioxide (ETCO(2)) and partial pressure of arterial carbon dioxide (PaCO(2) ) in very low birth weight infants (VLBWI); furthermore, we assessed factors that could affect the ETCO(2)-PaCO(2) relationship.

METHODS

Simultaneous end-tidal and arterial CO(2) pairs were obtained from ventilated VLBWI who were monitored by mainstream capnography and had umbilical arterial catheter. Correlation and agreement between ETCO(2) and PaCO(2) were evaluated by using Spearman test and Bland-Altman method, respectively.

RESULTS

A total of 143 simultaneous ETCO(2)-PaCO(2) pairs were analyzed from 45 ventilated VLBWI. There was a significant correlation (r = 0.69; P < 0.0001) between ETCO(2) and PaCO(2) values. The ETCO(2) value was lower than the corresponding PaCO(2) value in 94% pairs, with a mean bias of 13.5 ± 8.4 mmHg (95% agreement levels, -3.0 to 29.9 mmHg). Mean PaCO(2)-ETCO(2) bias was similar between ELBWI (13.1 ± 7.7 mmHg; 95% agreement levels, -1.9 and 28.2 mmHg) and infants with birth weight 1,001-1,500 g (14.8 ± 9.7 mmHg; 95% agreement levels -4.3 and 33.8 mmHg). The bias between ETCO(2) and PaCO(2) was significantly increased with increasing FiO(2), mean airway pressure and oxygenation index. Within each patient, there was a positive correlation (r = 0.78, P < 0.0001) between the changes in PaCO(2) and the simultaneous changes in ETCO(2).

CONCLUSIONS

In ventilated VLBWI, the correlation between mainstream ETCO(2) and PaCO(2) is good, but the agreement is poor and negatively influenced by the severity of pulmonary disease. Capnography is feasible in ELBWI. ETCO(2) should not replace PaCO(2) measurements in ventilated VLBWI, but may have a role to detect trends of PaCO(2).

Morbidity and mortality of neonatal respiratory failure in China: surfactant treatment in very immature infants

OBJECTIVES

We retrospectively investigated incidence, morbidity, and mortality of neonatal respiratory failure (NRF) in China, with special emphasis on surfactant treated very immature infants.

METHODS

NRF was defined as respiratory hypoxemia requiring mechanical ventilation and/or nasal continuous positive airway pressure for at least 24 hours.

RESULTS

There were 6864 cases of NRF, composing 19.7% of total admissions to 55 NICUs in 2008. Of these cases, 62.8% were preterm, and 16.4% of very low birth weight (VLBW, <1500 g). The primary diseases were respiratory distress syndrome (RDS, 43.9%), pneumonia/sepsis (21.7%), transient respiratory insufficiency (14.7%), transient tachypnea (8.1%), and meconium aspiration syndrome (7.0%). Surfactant was given to 26.8% of infants with NRF and 54.8% infants with RDS. The survival rate of surfactant-treated RDS was 79.9% compared to 71.8% in those not receiving surfactant (P < .001). This was also true in those of VLBW, 59.8% vs 52.2% (P = .035), respectively. The overall survival rate in NRF cases was 75.3%, but it was 58.1% among VLBW infants; for those infants of 25, 26, and 27 to 28 weeks' gestational age, the survival rates were ∼6%, 30%, and 50%, respectively; and the survival rates for infants with meconium aspiration syndrome and pneumonia/sepsis were 70.3% and 71.4%, respectively. The care burden was associated with high treatment withdrawal and death rate.

CONCLUSIONS

The outcomes of NRF, especially in extremely premature infants, reflect both progress and persistent limitations in providing respiratory support in the emerging NICUs of China, but overall survival for sick newborns had improved steadily.

Does after-hours in-house senior physician cover improve standard of care and outcomes in high-risk preterm neonates? A retrospective cohort study

AIM

To compare the standard of care and outcomes to discharge for inborn high-risk preterm (gestation <32 weeks) neonates admitted to the neonatal intensive care unit (NICU) before and after adopting an after-hours in-house senior physician cover roster (ISPCR). The ISPCR involved the presence of a consultant neonatologist or neonatal fellow in the NICU until 11 pm.

METHODS

This was a retrospective analysis of prospectively collected data for 12 months before (1 February 2002 to 31 January 2003, epoch 1) and after (1 April 2003 to 31 March 2004, epoch 2) adopting the ISPCR. Short-term neonatal outcomes, including mortality and morbidity such as intraventricular haemorrhage, retinopathy of prematurity, necrotising enterocolitis and chronic lung disease, were examined. The standard of acute care, including admission temperature, correct positioning of tubes and lines, and preventable ventilatory complications in the first 8 h following admission, was also compared.

RESULTS

The numbers (235 in epoch 1, 245 in epoch 2), demographic characteristics and severity of illness (CRIB score) of neonates admitted to the NICU was comparable between epochs. Overall neonatal outcomes did not show significant improvement after adopting an ISPCR, nor were they improved for after-hours admissions in the presence of senior in-house physicians. The standard of acute care was also not significantly different. Minor improvements, such as earlier administration of surfactant, were noted in epoch 2.

CONCLUSIONS

Adoption of an ISPCR was not associated with any significant change in the standard of acute care and short-term outcomes for inborn neonates <32 weeks' gestation.

Clinical characterization and long-term prognosis of neurological development in preterm infants with late-onset circulatory collapse

OBJECTIVE

To characterize the risk factors for late-onset circulatory collapse (LCC) in preterm infants responsive to corticosteroid therapy and evaluate the long-term neurological prognosis.

STUDY DESIGN

A retrospective case-control study for preterm infants (≤32 weeks' gestation) admitted to our neonatal intensive care unit from 1994 through 2002.

RESULT

Sixty-five infants (11%) were diagnosed with LCC. Infants with a shorter gestation and lower birth weight had a higher incidence of LCC. LCC infants had a significantly lower 1-min Apgar score, significantly higher incidence of severe intraventricular hemorrhage, chronic lung disease, and postnatal periventricular leukomalacia, and significantly longer duration of ventilation use, oxygen use, and hospital stay. Somatic growth at 36 weeks' postmenstrual age was poorer in infants with LCC than without LCC (controls). LCC infants were significantly more likely than controls to have cerebral palsy at 3 years.

CONCLUSION

LCC is associated with poor neurodevelopmental outcomes. Prevention of LCC can lead to improved neurological prognoses.

Detection of carbon dioxide thresholds using low-flow sidestream capnography in ventilated preterm infants

BACKGROUND

Monitoring CO2 levels in preterm infants receiving mechanical ventilation is designed to avoid the harmful consequences of hypocapnia or hypercapnia. Capnography is of questionable accuracy for monitoring PCO2 in preterm infants.

OBJECTIVES

To determine the accuracy of sidestream capnography in ventilated preterm infants by comparing end-tidal carbon dioxide (EtCO2) values to mixed venous carbon dioxide pressure (PvCO2) and to transcutaneous carbon dioxide pressure (TcPCO2).

METHODS

Simultaneous recordings of EtCO2, TcPCO2 and PvCO2 in 37 ventilated preterm infants. The PvCO2-EtCO2 gradient was calculated. The Bland-Altman technique and the intra-class correlation coefficient (ICC) were used to assess agreement between methods. The area under the curve (AUC) was calculated.

RESULTS

Ninety-nine EtCO2/PvCO2 pairs were studied from 37 preterm infants with a mean gestational age of 27.7 +/- 1.9 weeks and a mean birth weight of 1,003 +/- 331 g. The mean PvCO2-EtCO2 gradient was 11.2 +/- 8.0 mmHg, and the ICC was 0.28. The mean PvCO2-TcPCO2 gradient was 0 +/- 7.8 mmHg, and the ICC was 0.78. AUCs for EtCO2 and TcPCO2 were similar in detecting high or low PvCO2.

CONCLUSION

Despite an insufficient correlation between EtCO2 and PvCO2, capnography was able to detect low and high CO2 warning levels with a similar efficacy to that of TcPCO2, and may therefore be of clinical interest.

The role of systemic hemodynamic disturbances in prematurity-related brain injury

Premature infants who experience cerebrovascular injury frequently have acute and long-term neurologic complications. In this article, we explore the relationship between systemic hemodynamic insults and brain injury in this patient population and the mechanisms that might be at play.

The effect of changes in tPCO2 on the fractional tissue oxygen extraction--as measured by near-infrared spectroscopy--in neonates during the first days of life

The cerebral fractional oxygen extraction (FOE) reflects the balance between cerebral oxygen delivery (OD) and consumption (VO(2)). PCO(2) affects the cerebral blood flow (CBF): hypocapnia decreases CBF and OD and increases FOE. We recently showed that the fractional tissue oxygen extraction (FTOE) reflects FOE and hypothesized that a decrease in tPCO(2) increases FTOE. In this study we looked at the effect of changes in tPCO(2) on FTOE. We analysed 23 measurements in 13 neonates with birth weight below 1500 g and need for intensive care. Exclusion criteria were congenital malformations or cerebral complications. The tissue oxygenation index (TOI), tPCO(2), mean arterial blood pressure (MABP), heart rate (HR) and peripheral oxygen saturation (SaO(2)) were continuously recorded for 4h during the first days of life and FTOE was calculated. Over the whole group we found a significant negative (r=-0.227) correlation between tPCO(2) and FTOE and a significant positive (r=0.258) correlation between tPCO(2) and TOI. After correction for MABP these correlations remained significant. Over the whole group we found a significant positive correlation between tPCO(2) and TOI and a significant negative correlation between tPCO(2) and FTOE, which remained significant after correction for MABP. This implies that tPCO(2) influences the cerebral oxygenation independently of MABP. We therefore believe that for the interpretation of cerebral oxygenation in mechanically ventilated neonates during the first days of life continuous measurements of tPCO(2) are needed. Moreover we suggest FTOE to become a continuous parameter in the clinical setting for the non-invasive measurement of the neonatal brain oxygenation.

New and alternative modes of mechanical ventilation in neonates

Innovative ventilation modes for infants attempt to reduce volume-induced lung damage, to decrease airway pressure and oxygen exposure, and to improve patient comfort. Volume-targeted ventilation results in more consistent tidal volumes, allows automatic weaning of airway pressure, may avoid hypocapnia and may be associated with long-term clinical benefits. Pressure support ventilation allows the patient to control the duration of mechanical breaths. It requires a stable respiratory drive or back-up for apnoea. Pressure support ventilation may be effective for weaning. Proportional assist ventilation was studied in small animal species. In preterm infants with acute and chronic lung disease, ventilator pressure requirements were lower in cross-over short-term comparisons with conventional triggered ventilation. Neurally adjusted ventilatory assist delivers ventilator pressure in proportion and in synchrony with the phasic inspiratory diaphragmatic electrical activity obtained from intra-oesophageal electrodes. Large multicentre clinical trials are required to prove long-term clinical benefits of these new modes.

Prediction of periventricular leukomalacia. Part I: Selection of hemodynamic features using logistic regression and decision tree algorithms

OBJECTIVE

Periventricular leukomalacia (PVL) is part of a spectrum of cerebral white matter injury which is associated with adverse neurodevelopmental outcome in preterm infants. While PVL is common in neonates with cardiac disease, both before and after surgery, it is less common in older infants with cardiac disease. Pre-, intra-, and postoperative risk factors for the occurrence of PVL are poorly understood. The main objective of the present work is to identify potential hemodynamic risk factors for PVL occurrence in neonates with complex heart disease using logistic regression analysis and decision tree algorithms.

METHODS

The postoperative hemodynamic and arterial blood gas data (monitoring variables) collected in the cardiac intensive care unit of Children's Hospital of Philadelphia were used for predicting the occurrence of PVL. Three categories of datasets for 103 infants and neonates were used-(1) original data without any preprocessing, (2) partial data keeping the admission, the maximum and the minimum values of the monitoring variables, and (3) extracted dataset of statistical features. The datasets were used as inputs for forward stepwise logistic regression to select the most significant variables as predictors. The selected features were then used as inputs to the decision tree induction algorithm for generating easily interpretable rules for prediction of PVL.

RESULTS

Three sets of data were analyzed in SPSS for identifying statistically significant predictors (p<0.05) of PVL through stepwise logistic regression and their correlations. The classification success of the Case 3 dataset of extracted statistical features was best with sensitivity (SN), specificity (SP) and accuracy (AC) of 87, 88 and 87%, respectively. The identified features, when used with decision tree algorithms, gave SN, SP and AC of 90, 97 and 94% in training and 73, 58 and 65% in test. The identified variables in Case 3 dataset mainly included blood pressure, both systolic and diastolic, partial pressures pO(2) and pCO(2), and their statistical features like average, variance, skewness (a measure of asymmetry) and kurtosis (a measure of abrupt changes). Rules for prediction of PVL were generated automatically through the decision tree algorithms.

CONCLUSIONS

The proposed approach combines the advantages of statistical approach (regression analysis) and data mining techniques (decision tree) for generation of easily interpretable rules for PVL prediction. The present work extends an earlier research [Galli KK, Zimmerman RA, Jarvik GP, Wernovsky G, Kuijpers M, Clancy RR, et al. Periventricular leukomalacia is common after cardiac surgery. J Thorac Cardiovasc Surg 2004;127:692-704] in the form of expanding the feature set, identifying additional prognostic factors (namely pCO(2)) emphasizing the temporal variations in addition to upper or lower values, and generating decision rules. The Case 3 dataset was further investigated in Part II for feature selection through computational intelligence.

Prediction of periventricular leukomalacia. Part II: Selection of hemodynamic features using computational intelligence

OBJECTIVE

The objective of Part II is to analyze the dataset of extracted hemodynamic features (Case 3 of Part I) through computational intelligence (CI) techniques for identification of potential prognostic factors for periventricular leukomalacia (PVL) occurrence in neonates with congenital heart disease.

METHODS

The extracted features (Case 3 dataset of Part I) were used as inputs to CI based classifiers, namely, multi-layer perceptron (MLP) and probabilistic neural network (PNN) in combination with genetic algorithms (GA) for selection of the most suitable features predicting the occurrence of PVL. The selected features were next used as inputs to a decision tree (DT) algorithm for generating easily interpretable rules of PVL prediction.

RESULTS

Prediction performance for two CI based classifiers, MLP and PNN coupled with GA are presented for different number of selected features. The best prediction performances were achieved with 6 and 7 selected features. The prediction success was 100% in training and the best ranges of sensitivity (SN), specificity (SP) and accuracy (AC) in test were 60-73%, 74-84% and 71-74%, respectively. The identified features when used with the DT algorithm gave best SN, SP and AC in the ranges of 87-90% in training and 80-87%, 74-79% and 79-82% in test. Among the variables selected in CI, systolic and diastolic blood pressures, and pCO(2) figured prominently similar to Part I. Decision tree based rules for prediction of PVL occurrence were obtained using the CI selected features.

CONCLUSIONS

The proposed approach combines the generalization capability of CI based feature selection approach and generation of easily interpretable classification rules of the decision tree. The combination of CI techniques with DT gave substantially better test prediction performance than using CI and DT separately.

Cerebrovascular injury in premature infants: current understanding and challenges for future prevention

Cerebrovascular insults are a leading cause of brain injury in premature infants, contributing to the high prevalence of motor, cognitive, and behavioral deficits. Understanding the complex pathways linking circulatory immaturity to brain injury in premature infants remains incomplete. These mechanisms are significantly different from those causing injury in the mature brain. The gaps in knowledge of normal and disturbed cerebral vasoregulation need to be addressed. This article reviews current understanding of cerebral perfusion, in the sick premature infant in particular, and discusses challenges that lie ahead.

Hypercapnia and hypocapnia in neonates

BACKGROUND

The arterial partial pressure of carbon dioxide (PaCO2) represents the balance between CO2 production and consumption. Abnormal increase or decrease in PaCO2 can affect the body's internal environment and function. Permissive hypercapnia has aroused more attention as a novel ventilatory therapy. The aim of this study was to elucidate the effects of hypercapnia and hypocapnia on the functions of such neonatal organs as the lung and brain.

DATA SOURCES

The PubMed database was searched with the keywords "hypocapnia", "hypercapnia" and "newborn".

RESULTS

Hypocapnia is a risk factor for potential damage to the central nervous system, such as periventricular leukomalacia, intraventricular hemorrhage, cerebral palsy, cognition developmental disorder, and auditory deficit. Hyperventilation can lessen pulmonary artery hypertension to certain extent, but hypocapnia can aggravate ischemia/reperfusion-induced acute lung injury. Severe hypercapnia can induce intracranial hemorrhage, even consciousness alterations, cataphora, and hyperspasmia. Permissive hypercapnia can improve lung injury caused by diseases of the respiratory system, lessen mechanical ventilation-associated lung injury, reduce the incidence of bronchopulmonary dysplasia and protect against ventilation-induced brain injury. In addition, permissive hypercapnia plays a role in expanding cerebral vessels and increasing cerebral blood flow.

CONCLUSIONS

Severe hypercapnia and hypocapnia can cause neonatal brain injury and lung injury. Permissive hypercapnia can increase the survival of neonates with brain injury or respiratory system disease, and lessen the brain injury and lung injury caused by mechanical ventilation. However, the mechanism of permissive hypercapnia needs further exploration to confirm its safety and therapeutic utility.

Pathogenesis of cerebral white matter injury of prematurity

Cerebral white matter injury, characterised by loss of premyelinating oligodendrocytes (pre-OLs), is the most common form of injury to the preterm brain and is associated with a high risk of neurodevelopmental impairment. The unique cerebrovascular anatomy and physiology of the premature baby underlies the exquisite sensitivity of white matter to the abnormal milieu of preterm extrauterine life, in particular ischaemia and inflammation. These two upstream mechanisms can coexist and amplify their effects, leading to activation of two principal downstream mechanisms: excitotoxicity and free radical attack. Upstream mechanisms trigger generation of reactive oxygen and nitrogen species. The pre-OL is intrinsically vulnerable to free radical attack due to immaturity of antioxidant enzyme systems and iron accumulation. Ischaemia and inflammation trigger glutamate receptor-mediated injury leading to maturation-dependent cell death and loss of cellular processes. This review looks at recent evidence for pathogenetic mechanisms in white matter injury with emphasis on targets for prevention and treatment of injury.

Current definitions of hypotension do not predict abnormal cranial ultrasound findings in preterm infants

OBJECTIVE

Hypotension is a commonly treated complication of prematurity, although definitions and management guidelines vary widely. Our goal was to examine the relationship between current definitions of hypotension and early abnormal cranial ultrasound findings.

METHODS

We prospectively measured mean arterial pressure in 84 infants who were < or = 30 weeks' gestational age and had umbilical arterial catheters in the first 3 days of life. Sequential 5-minute epochs of continuous mean arterial pressure recordings were assigned a mean value and a coefficient of variation. We applied to our data 3 definitions of hypotension in current clinical use and derived a hypotensive index for each definition. We examined the association between these definitions of hypotension and abnormal cranial ultrasound findings between days 5 and 10. In addition, we evaluated the effect of illness severity (Score for Neonatal Acute Physiology II) on cranial ultrasound findings.

RESULTS

Acquired lesions as shown on cranial ultrasound, present in 34 (40%) infants, were not predicted by any of the standard definitions of hypotension or by mean arterial pressure variability. With hypotension defined as mean arterial pressure < 10th percentile (< 33 mmHg) for our overall cohort, mean value for mean arterial pressure and hypotensive index predicted abnormal ultrasound findings but only in infants who were > or = 27 weeks' gestational age and those with lower illness severity scores.

CONCLUSIONS

Hypotension as diagnosed by currently applied thresholds for preterm infants is not associated with brain injury on early cranial ultrasounds. Blood pressure management directed at these population-based thresholds alone may not prevent brain injury in this vulnerable population.

Relationship between serum lactate level and periventricular leukomalacia

In a case control study, we evaluated the serum lactate levels during the early days of life in preterm infants with periventricular leukomalacia (PVL), who were presumed to have suffered injury around birth. Thirteen infants diagnosed by ultrasonography as suffering from cystic PVL during the neonatal period and 26 normally developed infants matched by gestational age were enrolled in the study. The serum lactate level was measured repeatedly during the 72 h after birth. The mean serum lactate levels on admission were 2.95+/-0.43 and 3.21+/-0.29 mmol/L in the PVL and control groups, respectively. There was no statistically significant difference in the serum lactate level between the groups at any point during the first 72 h after birth. In conclusion, the serum lactate level was not elevated in preterm infants with PVL suggesting that the serum lactate level is not a useful predictor for the development of PVL in infants.

Relationship between white matter apparent diffusion coefficients in preterm infants at term-equivalent age and developmental outcome at 2 years

OBJECTIVE

The aim of this study was to develop a simple reproducible method for the measurement of apparent diffusion coefficient values in the white matter of preterm infants using diffusion-weighted imaging to test the hypothesis that elevated mean apparent diffusion coefficient values are associated with lower developmental quotient scores at 2 years' corrected age.

METHODS

We obtained diffusion-weighted imaging in 38 preterm infants at term-equivalent age who had no evidence of overt cerebral pathology on conventional MRI. Mean apparent diffusion coefficient values at the level of the centrum semiovale were determined. The children were assessed using a standardized neurologic examination, and the Griffiths Mental Development Scales were administered to obtain a developmental quotient at 2 years' corrected age. The relationship between mean apparent diffusion coefficient values and developmental quotient was examined. Clinical data relating to postnatal sepsis, antenatal steroid exposure, supplemental oxygen, gender, patent ductus arteriosus, and inotrope requirement were collected, and the mean apparent diffusion coefficient values for each group were compared.

RESULTS

The mean (+/-SD) apparent diffusion coefficient value in the white matter was 1.385 +/- 0.07 x 10(-3) mm2/second, and the mean developmental quotient was 108.9 +/- 11.5. None of the children had a significant neurologic problem. There was a significant negative correlation between mean apparent diffusion coefficient and developmental quotient.

CONCLUSION

These findings suggest that higher white matter apparent diffusion coefficient values at term-equivalent age in preterm infants without overt lesions are associated with poorer developmental performance in later childhood. Consequently, apparent diffusion coefficient values at term may be of prognostic value for neurodevelopmental outcome in infants who are born preterm and who have no other imaging indicators of abnormality.

Mild oliguria in preterm infants who later developed periventricular leukomalacia

The aim of this study is to determine whether or not renal involvement was present during the early neonatal period in preterm infants with PVL. We conducted a case-control study. The following items were evaluated; urine output, serum levels of sodium (Na), potassium (K), chloride (Cl), urea nitrogen (UN), and creatinine (Cr). The factors that could influence the urine output were also compared between the PVL and the control group. The mean urine output during the first 24h in the PVL group was 19.8ml/kg/day, and was significantly lower than in the control group (28.8ml/kg/day, p<0.05). The mean UN and Cr were not significantly different between the two groups. The minimal serum Na and Cl levels in the PVL group were significantly lower (128.3 and 94.3mEq/l) than those in the control group (134.8 and 100.7mEq/l, p<0.01 each). The maximal serum K level was significantly higher in the PVL group (6.47mEq/l) as compared to the control group (5.57mEq/l, p<0.05). There were no differences in any postnatal variables between the two groups. The preterm infants who later developed PVL had mild but significant oliguria during the first 24h of life. This suggests that preterm infants with PVL will have renal involvement immediately after birth.

Minimising neonatal brain injury: how research in the past five years has changed my clinical practice

With improving neonatal survival for extremely premature babies, the challenge for neonatology is to improve outcome of surviving babies. This review concentrates on best evidence emerging in recent years on prevention of brain damage by early administration of drugs as well as avoidance of induced brain damage by hyperventilation and dexamethasone therapy given postnatally for chronic lung disease.

Oxygenation and ventilation in spontaneously breathing very preterm infants with nasopharyngeal CPAP in the delivery room

AIM

To provide data on ventilation, oxygenation and acid-base state from birth to 48 h in very preterm infants treated with lung recruitment manoeuvre and nasopharyngeal continuous positive airway pressure in the delivery room.

METHODS

Subjects of this prospective observational cohort study were 48 of 61 infants enrolled in a randomised controlled trial to test two lung recruitment manoeuvres after birth. The infants had received an arterial line in the delivery room. The outcome measures were data on oxygenation, ventilation and acid-base state during spontaneous breathing.

RESULTS

Data are presented as (n [%]; median [minimum-maximum]). 22 of 48 (46%) infants (gestational age, 26.4 [25.0-28.9] weeks; birth weight 870 [540-1310] g) were never intubated during the study. The FiO(2) of these infants was low (0.4 [0.21-0.45] at 45 min and 0.21 [0.21-0.5] at 48 h). PCO(2) reached its maximum at 24 (11-44) min (8 [6.4-10.8] kPa) and decreased below 6.7 kPa (median) within 3 h. The incidence of intracranial haemorrhage/periventricular leukomalacia did not increase with hypercapnia (pCO(2) > 8 kPa).

CONCLUSION

A transient period of hypercapnia after birth may occur in spontaneously breathing very preterm infants supported with nasopharyngeal continuous positive airway pressure in the delivery room. The incidence of cerebral damage was not increased in infants with hypercapnia.

Cumulative index of exposure to hypocarbia and hyperoxia as risk factors for periventricular leukomalacia in low birth weight infants

BACKGROUND

Hypocarbia and hyperoxia are risk factors for periventricular leukomalacia in low birth weight infants. The association of a cumulative index of exposure to hypocarbia and hyperoxia and periventricular leukomalacia has not been evaluated.

OBJECTIVE

Our goal was to examine the relationship between cumulative index of exposure to hypocarbia and hyperoxia and periventricular leukomalacia during the first 7 days of life in low birth weight infants.

METHODS

Blood gas results were recorded in 6-hour intervals among low birth weight infants in a prospective data registry. Cumulative index of exposure to hypocarbia was calculated as the difference between arterial carbon dioxide level and 35 mmHg multiplied by the time interval in hours for each 6-hour block in a 24-hour day for the first 7 days of life. Cumulative index of exposure to hyperoxia was calculated in the same manner for arterial oxygen level >80 mm Hg. The relationship between exposure to hypocarbia, hyperoxia, and periventricular leukomalacia was examined in 778 infants with blood gas and cranial sonography data.

RESULTS

Twenty-one infants had periventricular leukomalacia. Hypocarbia occurred in 489 infants and hyperoxia in 502 infants. Infants with periventricular leukomalacia were more likely to have a lower gestational age and to require delivery room resuscitation than those without periventricular leukomalacia. More infants in the highest quartile of exposure to hypocarbia had periventricular leukomalacia compared to those with no hypocarbia. Risk of periventricular leukomalacia was increased in infants with the highest quartile of exposure to hypocarbia after adjusting for maternal and neonatal variables, none to be associated with periventricular leukomalacia. Cumulative index exposure to hyperoxia was not related to periventricular leukomalacia.

CONCLUSIONS

Cumulative exposure to hypocarbia and not hyperoxia was independently related to risk of periventricular leukomalacia in low birth weight infants.