Umbilical cord blood acid-base analysis at birth and long-term neurodevelopmental outcomes in children: a systematic review and meta-analysis

BACKGROUND

Umbilical cord blood acid-base sampling is routinely performed at many hospitals. Recent studies have questioned this practice and the association of acidosis with cerebral palsy.

OBJECTIVE

To investigate the associations between the results of umbilical cord blood acid-base analysis at birth and long-term neurodevelopmental outcomes and mortality in children.

SEARCH STRATEGY

We searched six databases using the search strategy: umbilical cord AND outcomes.

SELECTION CRITERIA

Randomised controlled trials, cohorts and case-control studies from high-income countries that investigated the association between umbilical cord blood analysis and neurodevelopmental outcomes and mortality from 1 year after birth in children born at term.

DATA COLLECTION AND ANALYSIS

We critically assessed the included studies, extracted data and conducted meta-analyses comparing adverse outcomes between children with and without acidosis, and the mean proportions of adverse outcomes. The certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluations approach.

MAIN RESULTS

We have very low confidence in the following findings: acidosis was associated with higher cognitive development scores compared with non-acidosis (mean difference 5.18, 95% CI 0.84-9.52; n = two studies). Children with acidosis also showed a tendency towards higher risk of death (relative risk [RR] 5.72, 95% CI 0.90-36.27; n = four studies) and CP (RR 3.40, 95% CI 0.86-13.39; n = four studies), although this was not statistically significant. The proportion of children with CP was 2.39/1000 across the studies, assessed as high certainty evidence.

CONCLUSION

Due to low certainty of evidence, the associations between umbilical cord blood gas analysis at delivery and long-term neurodevelopmental outcomes in children remains unclear.

Reduction in Perinatal Mortality after Implementation of HBB Training at a District Hospital in Mali

BACKGROUND

Mali has a high neonatal mortality rate of 38/1000 live births; in addition the fresh stillbirth rate (FSR) is 23/1000 births and of these one-third are caused by intrapartum events.

OBJECTIVES

The aims are to evaluate the effect of helping babies breathe (HBB) on mortality rate at a district hospital in Kati district, Mali.

METHODS

HBB first edition was implemented in April 2016. One year later the birth attendants were trained in HBB second edition and started frequent repetition training. This is a before and after study comparing the perinatal mortality during the period before HBB training with the period after HBB training, the period after HBB first edition and the period after HBB second edition. Perinatal mortality is defined as FSR plus neonatal deaths in the first 24 h of life.

RESULTS

There was a significant reduction in perinatal mortality rate (PMR) between the period before and after HBB training, from 21.7/1000 births to 6.0/1000 live births; RR 0.27, (95% CI 0.19-0.41; p < 0.0001). Very early neonatal mortality rate (24 h) decreased significantly from 6.3/1000 to 0.8/1000 live births; RR 0.12 (95% CI 0.05-0.33; p = 0.0006). FSR decreased from 15.7/1000 to 5.3/1000, RR 0.33 (95% CI 0.22-0.52; p < 0.0001). No further reduction occurred after introducing the HBB second edition.

CONCLUSION

HBB may be effective in a local first-level referral hospital in Mali.

Assessment of cerebral perfusion with contrast-enhanced ultrasound during constriction of the neck mimicking malposition of the BD Odon Device™: a study in newborn piglets

OBJECTIVE

The BD Odon Device™ is a new instrument for operative vaginal birth with potential for preventing maternal, fetal and newborn morbidity/mortality during a complicated second stage of labour. The device is a plastic sleeve with an air chamber inflated around the baby's head which is gently pulled through the birth canal. The aim was to monitor changes in cerebral circulation during constriction of the neck to evaluate a risk of potential malposition of the device.

DESIGN

Randomised prospective study.

POPULATION OR SAMPLE

Twelve newborn piglets.

METHODS

The anaesthetised piglets were exposed to hypoxia until base excess was -20 mmol/l and/or mean arterial blood pressure had decreased to 20 mmHg. At reoxygenation, an air chamber was inflated around the neck to 300 mmHg and the piglets randomised into three groups: 10 (n = 5), 5 (n = 5) or 2 (n = 2) minutes' occlusion. Cerebral perfusion was evaluated with transcranial contrast-enhanced ultrasound at four time-points, and analysed in the carotid arteries, basal ganglia, cortex and whole brain. Statistical analysis used ANOVA, linear mixed model, Kruskal-Wallis H-test.

MAIN OUTCOME MEASURES

Perfusion parameters; peak intensity, time to peak intensity, upslope, mean transit time, area under the curve.

RESULTS

The haemodynamic response was comparable between groups. Perfusion parameters showed a slight increase at end hypoxia followed by a decrease during occlusion, especially in the cortex (P = 0.00-0.2). After deflation, perfusion returned towards baseline values.

CONCLUSIONS

Simulation of malposition of the Odon Device was performed using a newborn hypoxic piglet model. Considerable compression of the neck vessels was applied, with only a moderate decrease in perfusion and with restoration of haemodynamics/cerebral perfusion after decompression.

TWEETABLE ABSTRACT

Malposition of Odon Device™ in a piglet model revealed a reversible decrease in cerebral perfusion during neck constriction.

Physical activity and the risk of preterm birth: a systematic review and meta-analysis of epidemiological studies

BACKGROUND

Physical activity has been inconsistently associated with risk of preterm birth, and the strength of the association and the shape of the dose-response relationship needs clarification.

OBJECTIVES

To conduct a systematic review and dose-response meta-analysis to clarify the association between physical activity and risk of preterm birth.

SEARCH STRATEGY

PubMed, Embase and Ovid databases were searched for relevant studies up to 9 February 2017.

SELECTION CRITERIA

Studies with a prospective cohort, case-cohort, nested case-control or randomized study design were included.

DATA COLLECTION AND ANALYSIS

Data were extracted by one reviewer and checked for accuracy by a second reviewer. Summary relative risks (RRs) were estimated using a random effects model.

MAIN RESULTS

Forty-one studies (43 publications) including 20 randomized trials and 21 cohort studies were included. The summary RR for high versus low activity was 0.87 [95% confidence interval (CI): 0.70-1.06, I² = 17%, n = 5] for physical activity before pregnancy, and it was 0.86 (95% CI: 0.78-0.95, I² = 0%, n = 30) for early pregnancy physical activity. The summary RR for a 3 hours per week increment in leisure-time activity was 0.90 (95% CI: 0.85-0.95, I² = 0%, n = 5). There was evidence of a nonlinear association between physical activity and preterm birth, P_nonlinearity < 0.0001, with the lowest risk observed at 2-4 hours per week of activity.

CONCLUSION

This meta-analysis suggests that higher leisure-time activity is associated with reduced risk of preterm birth. Further randomized controlled trials with sufficient frequency and duration of activity to reduce the risk and with larger sample sizes are needed to conclusively demonstrate an association.

TWEETABLE ABSTRACT

Physically active compared with inactive women have an 10-14% reduction in the risk of preterm birth.

The fetal circulation, pathophysiology of hypoxemic respiratory failure and pulmonary hypertension in neonates, and the role of oxygen therapy

Neonatal hypoxemic respiratory failure (HRF), a deficiency of oxygenation associated with insufficient ventilation, can occur due to a variety of etiologies. HRF can result when pulmonary vascular resistance (PVR) fails to decrease at birth, leading to persistent pulmonary hypertension of newborn (PPHN), or as a result of various lung disorders including congenital abnormalities such as diaphragmatic hernia, and disorders of transition such as respiratory distress syndrome, transient tachypnea of newborn and perinatal asphyxia. PVR changes throughout fetal life, evident by the dynamic changes in pulmonary blood flow at different gestational ages. Pulmonary vascular transition at birth requires an interplay between multiple vasoactive mediators such as nitric oxide, which can be potentially inactivated by superoxide anions. Superoxide anions have a key role in the pathophysiology of HRF. Oxygen (O2) therapy, used in newborns long before our knowledge of the complex nature of HRF and PPHN, has continued to evolve. Over time has come the discovery that too much O2 can be toxic. Recommendations on the optimal inspired O2 levels to initiate resuscitation in term newborns have ranged from 100% (pre 1998) to the currently recommended use of room air (21%). Questions remain about the most effective levels, particularly in preterm and low birth weight newborns. Attaining the appropriate balance between hypoxemia and hyperoxemia, and targeting treatments to the pathophysiology of HRF in each individual newborn are critical factors in the development of improved therapies to optimize outcomes.

Resuscitating preterm infants with 100% oxygen is associated with higher oxidative stress than room air

AIM

The starting fraction of inspired oxygen for preterm resuscitation is a matter of debate, and the use of room air in full-term asphyxiated infants reduces oxidative stress. This study compared oxidative stress in preterm infants randomised for resuscitation with either 100% oxygen or room air titrated to internationally recommended levels of preductal oxygen saturations.

METHODS

Blood was collected at birth, two and 12 hours of age from 119 infants <32 weeks of gestation randomised to resuscitation with either 100% oxygen (n = 60) or room air (n = 59). Oxidative stress markers, including advanced oxidative protein products (AOPP) and isoprostanes (IsoP), were measured with high-performance liquid chromatography and mass spectrometry.

RESULTS

Significantly higher levels of AOPP were found at 12 hours in the 100% oxygen group (p < 0.05). Increases between two- and 12-hour AOPP (p = 0.004) and IsoP (p = 0.032) concentrations were significantly higher in the 100% oxygen group.

CONCLUSION

Initial resuscitation with room air versus 100% oxygen was associated with lower protein oxidation at 12 hour and a lower magnitude of increase in AOPP and IsoP levels between two and 12 hours of life. Correlations with clinical outcomes will be vital to optimise the use of oxygen in preterm resuscitation.

Detection of batch effects in liquid chromatography-mass spectrometry metabolomic data using guided principal component analysis

Metabolomics based on liquid chromatography-mass spectrometry (LC-MS) is a powerful tool for studying dynamic responses of biological systems to different physiological or pathological conditions. Differences in the instrumental response within and between batches introduce unwanted and uncontrolled data variation that should be removed to extract useful information. This work exploits a recently developed method for the identification of batch effects in high throughput genomic data based on the calculation of a δ statistic through principal component analysis (PCA) and guided PCA. Its applicability to LC-MS metabolomic data was tested on two real examples. The first example involved the repeated analysis of 42 plasma samples and 6 blanks in three independent batches, and the second data set involved the analysis of 101 plasma and 18 blank samples in a single batch with a total runtime of 50h. The first and second data set were used to evaluate between and within-batch effects using the δ statistic, respectively. Results obtained showed the usefulness of using the δ statistic together with other approaches such as summary statistics of peak intensity distributions, PCA scores plots or the monitoring of IS peak intensities, to detect and identify instrumental instabilities in LC-MS.

New guidelines for newborn resuscitation--a critical evaluation

The 2010 International Liaison Committee on Resuscitation guidelines for newborn resuscitation represent important progress. The criteria for assessment are simplified based on heart rate and respiration only and there is no timing of stages after the first 60 sec. Instead of giving supplemental oxygen, the guidelines state that 'it is best to start with air'. However, the optimal oxygen concentration later in the process and for premature babies is not yet clear. A description of an adequate heart rate response is not given, and the cut-off of 100 bpm may be arbitrary. There are still no clear recommendations regarding ventilation, inspiratory time, use of positive end expiratory pressure or continuous positive airway pressure. The guidelines do not mention which paCO2 level might be optimal. As colour pink assessment and routine suctioning of airways are not recommended anymore, there is an urgent need to obtain international consensus and create a new and revised Apgar score without these two variables.

CONCLUSION

In spite of improved guidelines for newborn resuscitation, there is still a number of unanswered questions and a need for more delivery room studies.

Resuscitation of the term and preterm infant

Resuscitation is one of the most frequently performed procedures in the neonatal period. Since the most recent guidelines from the International Liaison Committee on Resuscitation (ILCOR) appeared in 2005, experimental and clinical research has introduced changes regarding the different components of the procedure, with the common denominator being the least aggressive to the baby. Babies should be kept warm, avoiding suctioning as a general rule, adjusting pressure, volume and oxygen to the minimum to achieve stabilisation without causing harm to the airways or oxidative stress, and applying all the available technology in the delivery room before transportation to the neonatal intensive care unit. The response to ventilation should primarily be assessed by the heart rate. Babies of gestational age >or=32 weeks should be ventilated initially with 21% oxygen and if <32 weeks with 21-30% oxygen. Intubation, chest compressions, use of drugs or volume therapy are rarely needed in term or near term babies in need of resuscitation. The first minutes of life are decisive, and what we do during these minutes will have unequivocal influence later on.

Release of hypoxanthine and phosphate from exercising human legs with and without arterial insufficiency

Release of hypoxanthine and phosphate from exercising legs was studied in eight subjects without known obstructive arterial disease and in 20 claudicants. Lower leg blood flow was measured with a thermodilution catheter in the popliteal/distal femoral vein. The catheter allowed blood sampling from the calf before, during and after exhaustive exercise on a bicycle ergometer at a stepwise increasing load. Resting plasma hypoxanthine levels were higher in claudicants than in normal subjects (p less than 0.05). Hypoxanthine concentrations increased 2-4-fold during exercise, amounting to values ten times higher than the resting levels 5 and 10 min post exercise, in the venous effluent of the normal legs. A similar rise was found in the claudicants despite half the exercise intensity at exhaustion. Popliteal venous concentrations of phosphate increased by approximately 25% during exercise without significant differences between the two groups. During exercise the release of hypoxanthine increased 38-fold and of phosphate 21-fold in the normal lower legs, while a ten-fold increase in both metabolites was recorded in the claudicating legs. The study demonstrated a high release of hypoxanthine and phosphate from the human lower leg during rhythmic, exhaustive exercise (with maximal vasodilation). The result is compatible with the assumption that metabolites from the catabolism of adenine nucleotides (adenosine) play a role in the autoregulation of blood flow in human skeletal muscle. Increased plasma hypoxanthine concentrations at rest may indicate peripheral arterial insufficiency.

High activities of erythrocyte glutathione peroxidase in patients with the Lesch-Nyhan syndrome

Antioxidant levels were determined in five patients with the Lesch-Nyhan syndrome. The erythrocyte glutathione peroxidase activity was in average 1.8 times higher in Lesch-Nyhan patients than in controls (1.68 +/- 0.36 versus 0.92 +/- 0.17 mu kat/g hemoglobin, p less than 0.001). Plasma CuZn-superoxide dismutase activity was two times higher (p less than 0.001) and Mn-superoxide dismutase activity was 1.5 times higher (p less than 0.05) than in controls, whilst erythrocyte CuZn-superoxide dismutase, plasma extracellular-superoxide dismutase and lymphocyte superoxide dismutase did not differ between Lesch-Nyhan patients and healthy controls. These data might indicate that Lesch-Nyhan patients are exposed to a higher oxidative load than healthy control persons.

Population and disease-based prevalence of the common mutations associated with surfactant deficiency

The prevalence of the common mutations in the surfactant protein-B (121ins2), surfactant protein-C (I73T), and ATP-binding cassette member A3 (E292V) genes in population-based or case-control cohorts of newborn respiratory distress syndrome (RDS) is unknown. We determined the frequencies of these mutations in ethnically diverse population and disease-based cohorts using restriction enzyme analysis (121ins2 and E292V) and a 5' nuclease assay (I73T) in DNA samples from population-based cohorts in Missouri, Norway, South Korea, and South Africa, and from a case-control cohort of newborns with and without RDS (n = 420). We resequenced the ATP-binding cassette member A3 gene (ABCA3) in E292V carriers and computationally inferred ABCA3 haplotypes. The population-based frequencies of 121ins2, E292V, and I73T were rare (<0.4%). E292V was present in 3.8% of newborns with RDS, a 10-fold greater prevalence than in the Missouri cohort (p < 0.001). We did not identify other loss of function mutations in ABCA3 among patients with E292V that would account for their RDS. E292V occurred on a unique haplotype that was derived from a recombination of two common ABCA3 haplotypes. E292V was over-represented in newborns with RDS suggesting that E292V or its unique haplotype impart increased genetic risk for RDS.

Oxygen and retinopathy of prematurity

Retinopathy of prematurity is on the rise and a third epidemic has been identified. In spite of extensive research and progress in the understanding of this disease in recent years, 50 000 children worldwide are blinded by this condition each year. The relation between hyperoxia, low-gestational age, growth retardation, oxygen dependent growth factors, and oxidative stress are now being understood more clearly. We know that in the first phase of retinopathy of prematurity, hyperoxia inhibits vascular endothelial growth factor. In the second phase, vascular endothelial growth factor rises, and when insulin-like growth factor-1 reaches a threshold around 32 to 34 weeks postconceptional age, uncontrolled neovascularization may occur. It is not known whether this new knowledge will have implications for future therapy. However, by strictly avoiding hyperoxia, that is, SaO2>92-93% and avoiding fluctuations in SaO2, it is possible to control and prevent severe retinopathy of prematurity in most cases.

Restoration of cardiopulmonary function with 21% versus 100% oxygen after hypoxaemia in newborn pigs

OBJECTIVE

To assess the consequences of hypoxaemia and resuscitation with room air versus 100% O(2) on cardiac troponin I (cTnI), cardiac output (CO), and pulmonary artery pressure (PAP) in newborn pigs.

DESIGN

Twenty anaesthetised pigs (12-36 hours; 1.7-2.7 kg) were subjected to hypoxaemia by ventilation with 8% O(2). When mean arterial blood pressure fell to 15 mm Hg, or arterial base excess was < or = -20 mmol/l, resuscitation was performed with 21% (n = 10) or 100% (n = 10) O(2) for 30 minutes, then ventilation with 21% O(2) for 120 minutes. Blood was analysed for cTnI. Ultrasound examinations of CO and PAP (estimated from tricuspid regurgitation velocity (TR-Vmax)) were performed at baseline, during hypoxia, and at the start of and during reoxygenation.

RESULTS

cTnI increased from baseline to the end point (p<0.001), confirming a serious myocardial injury, with no differences between the 21% and 100% O(2) group (p = 0.12). TR-Vmax increased during the insult and returned towards baseline values during reoxygenation, with no differences between the groups (p = 0.11) or between cTnI concentrations (p = 0.31). An inverse relation was found between increasing age and TR-Vmax during hypoxaemia (p = 0.034). CO per kg body weight increased during the early phase of hypoxaemia (p<0.001), then decreased. Changes in CO per kg were mainly due to changes in heart rate, with no differences between the groups during reoxygenation (p = 0.298).

CONCLUSION

Hypoxaemia affects the myocardium and PAP. During this limited period of observation, reoxygenation with 100% O(2) showed no benefits compared with 21% O(2) in normalising myocardial function and PAP. The important issue may be resuscitation and reoxygenation without hyperoxygenation.

Meconium Aspiration Syndrome Induces Complement-Associated Systemic Inflammatory Response in Newborn Piglets

The pathophysiology of meconium aspiration syndrome (MAS) is complex. We recently showed that meconium is a potent activator of complement. In the present study, we investigated whether the complement activation occurring in experimental MAS is associated with a systemic inflammatory response as judged by granulocyte activation and cytokine and chemokine release. MAS was induced by the instillation of meconium into the lungs of newborn piglets (n = 8). Control animals (n = 5) received saline under otherwise identical conditions. Haemodynamic and lung dynamic data were recorded. Complement activation, revealed by the terminal sC5b-9 complex (TCC), and cytokines [interleukin (IL)-6 and IL-8] were measured in plasma samples by enzyme immunoassays. The expression of CD18, CD11b and oxidative burst in granulocytes was measured in whole blood by flow cytometry. Plasma TCC increased rapidly in the MAS animals in contrast with controls (P < 0.0005). The TCC concentration correlated closely with oxygenation index (r = 0.48, P < 0.0005) and ventilation index (r = 0.57, P < 0.0005) and inversely with lung compliance (r = -0.63, P < 0.0005). IL-6 and IL-8 increased in MAS animals compared with the controls (P = 0.002 and P < 0.001, respectively). Granulocyte oxidative burst declined significantly in the MAS animals compared with the controls (P < 0.02). TCC correlated significantly with IL-6 (r = 0.64, P < 0.0005) and IL-8 (r = 0.32; P = 0.03) and inversely with oxidative burst (r = -0.37; P = 0.02). A systemic inflammatory response associated with complement activation is seen in experimental MAS. This reaction may contribute to the pathogenesis of MAS.

Increased myocardial matrix metalloproteinases in hypoxic newborn pigs during resuscitation: effects of oxygen and carbon dioxide

BACKGROUND

Perinatal asphyxia is associated with cardiac dysfunction, and it is important to prevent further tissue injury during resuscitation. There is increasing evidence that myocardial matrix metalloproteinases (MMPs) are involved in myocardial hypoxaemia-reoxygenation injury.

OBJECTIVE

To assess MMPs and antioxidant capacity in newborn pigs after global ischaemia and subsequent resuscitation with ambient air or 100% O(2) at different PaCO(2)-levels.

METHODS

Newborn pigs (12-36 h of age) were resuscitated for 30 min by ventilation with 21% or 100% O(2) at different PaCO(2) levels after a hypoxic insult, and thereafter observed for 150 min. In myocardial tissue extracts, MMPs were analyzed by gelatin zymography and broad matrix-degrading capacity (total MMP). Total endogenous antioxidant capacity in myocardial tissue extracts was measured by the oxygen radical absorbance capacity (ORAC) assay.

RESULTS

Matrix metalloproteinase-2 more than doubled from baseline values (P < 0.001), and was higher in piglets resuscitated with 100% O(2) than with ambient air (P = 0.012). The ORAC value was considerably decreased (P < 0.001). In piglets with elevated PaCO(2), total MMP-activity in the right ventricle was more increased than in the left ventricle (P = 0.008). In the left ventricle, total MMPactivity was higher in the piglets with low PaCO(2) than in the piglets with elevated PaCO(2) (P = 0.013).

CONCLUSION

In hypoxaemia-reoxygenation injury the MMP-2 level was highly increased and was most elevated in the piglets resuscitated with 100% O(2). Antioxidant capacity was considerably decreased. Assessed by total MMP-activity, elevated PaCO(2) during resuscitation might protect the left ventricle, and probably increase right ventricle injury of the myocardium.

Resuscitation with 100% O(2) does not protect the myocardium in hypoxic newborn piglets

BACKGROUND

Perinatal asphyxia is associated with cardiac dysfunction secondary to myocardial ischaemia. Cardiac troponin I (cTnI) is a marker of myocardial necrosis. Raised concentrations in the blood are related to perinatal asphyxia and increased morbidity.

OBJECTIVE

To assess porcine myocardial damage from enzyme release during hypoxaemia induced global ischaemia, and subsequent resuscitation with ambient air or 100% O(2). To investigate whether CO(2) level during resuscitation influences myocardial damage.

DESIGN

Newborn piglets (12-36 hours) were exposed to hypoxaemia by ventilation with 8% O(2) in nitrogen. When mean arterial blood pressure had fallen to 15 mm Hg, or base excess to < -20 mmol/l, the animals were randomly resuscitated by ventilation with either 21% O(2) (group A, n = 29) or 100% O(2) (group B, n = 29) for 30 minutes. Afterwards they were observed in ambient air for another 150 minutes. During resuscitation, the two groups were further divided into three subgroups with different CO(2) levels.

ANALYSIS

Blood samples were analysed for cTnI, myoglobin, and creatine kinase-myocardial band (CK-MB) at baseline and at the end of the study.

RESULTS

cTnI increased more than 10-fold (p < 0.001) in all the groups. Myoglobin and CK-MB doubled in concentration.

CONCLUSION

The considerable increase in cTnI indicates seriously affected myocardium. Reoxygenation with 100% oxygen offered no biochemical benefit over ambient air. CK-MB and myoglobin were not reliable markers of myocardial damage. Normoventilation tended to produce better myocardial outcome than hyperventilation or hypoventilation.