Research on the relationship between brain anoxia at different regional oxygen saturations and brain damage using near-infrared spectroscopy

Assessment of Autoregulation of the Cerebral Circulation during Acute Lung Injury in a Neonatal Porcine Model

In neonates with acute lung injury (ALI), targeting lower oxygenation saturations is suggested to limit oxygen toxicity while maintaining vital organ function. Although thresholds for cerebral autoregulation are studied for the management of premature infants, the impact of hypoxia on hemodynamics, tissue oxygen consumption and extraction is not well understood in term infants with ALI. We examined hemodynamics, cerebral autoregulation and fractional oxygen extraction, as measured by near-infrared spectroscopy (NIRS) and blood gases, in a neonatal porcine oleic acid injury model of moderate ALI. We hypothesized that in ALI animals, cerebral oxygen extraction would be increased to a greater degree than kidney or gut oxygen extraction as indicative of the brain's adaptive efforts to increase cerebral oxygen extraction at the expense of splanchnic end organs. Fifteen anesthetized, ventilated 5-day-old neonatal piglets were divided into moderate lung injury by treatment with oleic acid or control (sham injection). The degree of lung injury was quantified at baseline and after establishment of ALI by blood gases, ventilation parameters and calculated oxygenation deficit, hemodynamic indices by echocardiography and lung injury score by ultrasound. PaCO2 was maintained constant during ventilation. Cerebral, renal and gut oxygenation was determined by NIRS during stepwise decreases in inspired oxygen from 50% to 21%, correlated with PaO2 and PvO2; changes in fractional oxygen extraction (ΔFOE) were calculated from NIRS and from regional blood gas samples. The proportion of cerebral autoregulation impairment attributable to blood pressure, and to hypoxemia, was calculated from autoregulation nomograms. ALI manifested as hypoxemia with increasing intrapulmonary shunt fraction, decreased lung compliance and increased resistance, and marked increase in lung ultrasound score. Brain, gut and renal NIRS, obtained from probes placed over the anterior skull, central abdomen and flank, respectively, correlated with concurrent SVC (brain) or IVC (gut, renal) PvO2 and SvO2. Cerebral autoregulation was impaired after ALI as a function of blood pressure at all FiO2 steps, but predominantly by hypoxemia at FiO2 < 40%. Cerebral ΔFOE was higher in ALI animals at all FiO2 steps. We conclude that in an animal model of neonatal ALI, cerebrovascular blood flow regulation is primarily dependent on oxygenation. There is not a defined oxygenation threshold below which cerebral autoregulation is impaired in ALI. Cerebral oxygen extraction is enhanced in ALI, reflecting compensation for exhausted cerebral autoregulation due to the degree of hypoxemia and/or hypotension, thereby protecting against tissue hypoxia.

Delayed Surgical Closure of the Patent Ductus Arteriosus: Does the Brain Pay the Price?

OBJECTIVE

To investigate the relation between duration of hemodynamically significant patent ductus arteriosus (PDA), cerebral oxygenation, magnetic resonance imaging-determined brain growth, and 2-year neurodevelopmental outcome in a cohort of infants born preterm whose duct was closed surgically.

STUDY DESIGN

Infants born preterm at <30 weeks of gestational age who underwent surgical ductal closure between 2008 and 2018 (n = 106) were included in this observational study. Near infrared spectroscopy-monitored cerebral oxygen saturation during and up to 24 hours after ductal closure and a Bayley III developmental test at the corrected age of 2 years is the institutional standard of care for this patient group. Infants also had magnetic resonance imaging at term-equivalent age.

RESULTS

In total, 90 infants fulfilled the inclusion criteria (median [range]: 25.9 weeks [24.0-28.9]; 856 g [540-1350]. Days of a PDA ranged from 1 to 41. Multivariable linear regression analysis showed that duration of a PDA negatively influenced cerebellar growth and motor and cognitive outcome at 2 years of corrected age.

CONCLUSIONS

Prolonged duration of a PDA in this surgical cohort is associated with reduced cerebellar growth and suboptimal neurodevelopmental outcome.

Protecting the brain of the micropreemie

Advances in perinatal care have seen substantial improvements in survival without disability for extremely preterm infants. Protecting the developing brain and reducing neurodevelopmental sequelae of extremely preterm birth are strategic priorities for both research and clinical care. A number of evidence-based interventions exist for neuroprotection in micropreemies, inclusive of prevention of preterm birth and multiple births with implantation of only one embryo during in vitro fertilisation, as well as antenatal care to optimize fetal wellbeing, strategies for supporting neonatal transition, and neuroprotective developmental care. Avoidance of complications that trigger ischemia and inflammation is vital for minimizing brain dysmaturation and injury, particularly of the white matter. Neurodevelopmental surveillance, early diagnosis of cerebral palsy and early intervention are essential for optimizing long-term outcomes and quality of life. Research priorities include further evaluation of putative neuroprotective agents, and investigation of common neonatal interventions in trials adequately powered to assess neurodevelopmental outcome.

Brain temperature monitoring in newborn infants: Current methodologies and prospects

Brain tissue temperature is a dynamic balance between heat generation from metabolism, passive loss of energy to the environment, and thermoregulatory processes such as perfusion. Perinatal brain injuries, particularly neonatal encephalopathy, and seizures, have a significant impact on the metabolic and haemodynamic state of the developing brain, and thereby likely induce changes in brain temperature. In healthy newborn brains, brain temperature is higher than the core temperature. Magnetic resonance spectroscopy (MRS) has been used as a viable, non-invasive tool to measure temperature in the newborn brain with a reported accuracy of up to 0.2 degrees Celcius and a precision of 0.3 degrees Celcius. This measurement is based on the separation of chemical shifts between the temperature-sensitive water peaks and temperature-insensitive singlet metabolite peaks. MRS thermometry requires transport to an MRI scanner and a lengthy single-point measurement. Optical monitoring, using near infrared spectroscopy (NIRS), offers an alternative which overcomes this limitation in its ability to monitor newborn brain tissue temperature continuously at the cot side in real-time. Near infrared spectroscopy uses linear temperature-dependent changes in water absorption spectra in the near infrared range to estimate the tissue temperature. This review focuses on the currently available methodologies and their viability for accurate measurement, the potential benefits of monitoring newborn brain temperature in the neonatal intensive care unit, and the important challenges that still need to be addressed.

Near-infrared spectroscopy for perioperative assessment and neonatal interventions

Perioperative applications of near-infrared spectroscopy (NIRS) to monitor regional tissue oxygenation and perfusion in cardiac and noncardiac surgery are of increasing interest in neonatal care. Complex neonatal surgery can impair adequate oxygen delivery and tissue oxygen consumption and increase the risk of neurodevelopmental delay. Coupled with conventional techniques, NIRS monitoring may enable targeted hemodynamic management of the circulation in both cardiac and noncardiac surgical procedures. In this narrative review, we discuss the application of perioperative NIRS in specific neonatal interventions, including surgical intervention for congenital heart defects, definitive closure of the patent ductus arteriosus, neurological and gastrointestinal disorders, and use of extracorporeal membrane oxygenation. We identified areas for future research within disease-specific indications and offer a roadmap to aid in developing evidence-based targeted diagnostic and management strategies in neonates. IMPACT: There is growing recognition that perioperative NIRS monitoring, used in conjunction with conventional monitoring, may provide critical hemodynamic information that either complements clinical impressions or delivers novel physiologic insight into the neonatal circulatory and perfusion pathways.

Neuroprotection of the Perinatal Brain by Early Information of Cerebral Oxygenation and Perfusion Patterns

Abnormal patterns of cerebral perfusion/oxygenation are associated with neuronal damage. In preterm neonates, hypoxemia, hypo-/hypercapnia and lack of cerebral autoregulation are related to peri-intraventricular hemorrhages and white matter injury. Reperfusion damage after perinatal hypoxic ischemia in term neonates seems related with cerebral hyperoxygenation. Since biological tissue is transparent for near infrared (NIR) light, NIR-spectroscopy (NIRS) is a noninvasive bedside tool to monitor brain oxygenation and perfusion. This review focuses on early assessment and guiding abnormal cerebral oxygenation/perfusion patterns to possibly reduce brain injury. In term infants, early patterns of brain oxygenation helps to decide whether or not therapy (hypothermia) and add-on therapies should be considered. Further NIRS-related technical advances such as the use of (functional) NIRS allowing simultaneous estimation and integrating of heart rate, respiration rate and monitoring cerebral autoregulation will be discussed.

Near-Infrared Spectroscopy Monitoring of Cerebral Oxygenation and Influencing Factors in Neonates from High-Altitude Areas

BACKGROUND

Accurate detection of cerebral oxygen saturation (rSO2) may be useful for neonatal brain injury prevention, and the normal range of rSO2 of neonates at high altitude remained unclear.

OBJECTIVE

To compare cerebral rSO2 and cerebral fractional tissue oxygen extraction (cFTOE) at high-altitude and low-altitude areas in healthy neonates and neonates with underlying diseases.

METHODS

515 neonates from low-altitude areas and 151 from Tibet were enrolled. These neonates were assigned into the normal group, hypoxic-ischemic encephalopathy (HIE) group, and other diseases group. Near-infrared spectroscopy was used to measure rSO2 in neonates within 24 h after admission. The differences of rSO2, pulse oxygen saturation (SpO2), and cFTOE levels were compared between neonates from low- and high-altitude areas.

RESULTS

(1) The mean rSO2 and cFTOE levels in normal neonates from Tibet were 55.0 ± 6.4% and 32.6 ± 8.5%, significantly lower than those from low-altitude areas (p < 0.05). (2) At high altitude, neonates with HIE, pneumonia (p < 0.05), anemia, and congenital heart disease (p < 0.05) have higher cFTOE than healthy neonates. (3) Compared with HIE neonates from plain areas, neonates with HIE at higher altitude had lower cFTOE (p < 0.05), while neonates with heart disease in plateau areas had higher cFTOE than those in plain areas (p < 0.05).

CONCLUSIONS

The rSO2 and cFTOE levels in normal neonates from high-altitude areas are lower than neonates from the low-altitude areas. Lower cFTOE is possibly because of an increase in blood flow to the brain, and this may be adversely affected by disease states which may increase the risk of brain injury.

Interrelations of Intraoperative Changes in Cerebral Tissue Oxygen Saturation with Brain Volumes and Neurodevelopment Outcome After the Comprehensive Stage II Procedure in Infants With Hypoplastic Left Heart Syndrome: A Retrospective Cohort Study

OBJECTIVES

The monitoring of cerebral tissue oxygen saturation by near-infrared spectroscopy (S_cerebO₂) is used widely in pediatric cardiac anesthesia. However, little information is available on the effects of changes in perioperative S_cerebO₂ on brain morphology and neurologic outcome. The primary hypothesis tested in this study was that intraoperative S_cerebO₂ during the comprehensive stage II procedure correlated with brain volumes assessed by magnetic resonance imaging and neurodevelopmental scores.

DESIGN

Retrospective observational cohort study.

SETTING

University Hospital, Pediatric Heart Centre.

PATIENTS AND MEASUREMENTS

In 19 infants, the intraoperative course of S_cerebO₂ during the comprehensive stage II procedure was examined. Minimal S_cerebO₂ and integrated S_cerebO₂ below 45% (AUC) during surgery, as well as cerebral magnetic resonance imaging (MRI) examinations and Bayley III test at the ages of two-to-three years, were analyzed.

MAIN RESULTS

A positive correlation between minimal S_cerebO₂ and intracranial volume (p = 0.0243), total brain volume (p = 0.0243), and white matter volume (p = 0.0276) was observed, as was a negative correlation between AUC and intracranial volume (p = 0.0454) and white matter volume (p = 0.0381), respectively. No association was found between S_cerebO₂ and Bayley-III Score.

CONCLUSION

The correlation between S_cerebO₂ and brain volumes measured by MRI pointed out a possible importance of neuroprotective strategies aimed at optimizing S_cerebO₂ during complex congenital heart surgery. That no correlation between S_cerebO₂ and Bayley III Score was found suggested multifactorial causes for neurologic outcome in children with congenital heart defects.

Cerebral Oxygenation and Autoregulation in Preterm Infants (Early NIRS Study)

OBJECTIVE

To determine if decreased cerebral oxygenation or altered cerebral autoregulation as measured by near-infrared spectroscopy (NIRS) in the first 96 postnatal hours is associated with an increased risk of death or severe neuroradiographic abnormalities in very preterm infants.

STUDY DESIGN

The Early NIRS prospective, multicenter study enrolled very preterm infants with a birth weight of <1250 g from 6 tertiary neonatal intensive care units. Mean arterial blood pressure and cerebral oxygen saturation (Csat) were continuously monitored using a neonatal sensor until 96 hours of age. Moving window correlations between Csat and mean arterial blood pressure determined time periods with altered cerebral autoregulation, and percentiles of correlation were compared between infants with and without the adverse outcome of mortality or severe neuroradiographic abnormalities by early cranial ultrasound.

RESULTS

Of 103 subjects with mean gestational age of 26 weeks, 21 (20%) died or had severe neuroradiographic abnormalities. Infants with adverse outcomes had a lower mean Csat (67 ± 9%) compared with those without adverse outcomes (72 ± 7%; P = .02). A Csat of <50% was identified as a cut-point for identifying infants with adverse outcome (area under the curve, 0.76). Infants with adverse outcomes were more likely to have significant positive or negative correlations between Csat and mean arterial blood pressure, indicating impaired cerebral autoregulation (P = .006).

CONCLUSIONS

Early NIRS monitoring may detect periods of lower cerebral oxygenation and altered cerebral autoregulation, identifying preterm infants at risk for mortality or neuroradiographic injury. An improved understanding of the relationship between altered hemodynamics and cerebral oxygenation may inform future strategies to prevent brain injury.

Near-Infrared spectroscopy for perfusion assessment and neonatal management

Term and preterm infants often present with adverse conditions after birth resulting in abnormal vital functions and severe organ failure, which are associated or sometimes caused by low oxygen and/or blood supply. Brain injury may lead to substantial mortality and morbidity often affecting long-term outcome. Standard monitoring techniques in the NICU focus on arterial oxygen supply and hemodynamics and include respiratory rate, heart rate, blood pressure and arterial oxygen saturation as measured by pulse oximetry but provide only limited information on end organ oxygen delivery. Near-Infrared Spectroscopy can bridge this gap by displaying continuous measurements of tissue oxygen saturation, providing information on the balance of oxygen delivery and consumption in organs of interest. Future techniques using multi-wavelength devices may provide additional information on oxidative metabolism in real time adding important information.

[Near-infrared spectroscopy : Technique, development, current use and perspectives]

Near-infrared spectroscopy (NIRS) has been available in research and clinical practice for more than four decades. Recently, there have been numerous publications and substantial developments in the field. This article describes the clinical application of NIRS in relation to current guidelines, with a focus on pediatric and cardiac anesthesia. It discusses technical and physiological principles, pitfalls in clinical use and presents (patho)physiological influencing factors and derived variables, such as fractional oxygen extraction (FOE) and the cerebral oxygen index (COx). Recommendations for the interpretation of NIRS values in connection with influencing factors, such as oxygen transport capacity, gas exchange and circulation as well as an algorithm for cardiac anesthesia are presented. Limitations of the method and the lack of comparability of values from different devices as well as generally accepted standard values are explained. Technical differences and advantages compared to pulse oxymetry and transcranial Doppler sonography are illuminated. Finally, the prognostic significance and requirements for future clinical studies are discussed.

Cerebral Oxygenation in Preterm Infants With Necrotizing Enterocolitis

BACKGROUND AND OBJECTIVES

Preterm infants with necrotizing enterocolitis (NEC) are known to have worse neurodevelopmental outcomes, but there is no substantial evidence to support an underlying pathophysiology. We aimed to examine whether cerebral oxygenation differs in those infants who develop NEC compared to cerebral oxygenation in those who do not.

METHODS

We examined 48 infants <30 weeks' gestation admitted to a tertiary level NICU from October 2016 to May 2018. Infants with birth weight less than or equal to the second percentile, abnormal antenatal dopplers or twin-to-twin-transfusion-syndrome were excluded. Cerebral oximetry measurements were performed by using a near-infrared spectroscopy (NIRS) monitor weekly for 60 minutes, allowing measurement of cerebral tissue oxygenation index from the first week of life to 36 weeks postconceptional age. Weekly clinical status was also recorded. NEC was defined as greater than or equal to Bell stage 2.

RESULTS

The median birth weight was 884 g (range of 460-1600 g), the median weeks' gestational age was 26 + 3/7 (23 + 0/7 to 29 + 6/7), and 52% were girls. In total, 276 NIRS measurements were completed, and 7 infants developed NEC. NIRS measurements from 1 infant with NEC and 4 infants without NEC who developed hemorrhagic parenchymal infarcts were excluded from analysis. Infants who developed NEC had significantly lower cerebral tissue oxygenation index than those who did not (P = .011), even when adjusted for confounders, including gestational age, birth weight, patent ductus arteriosus, enteral feeds, sex, ethnicity, and hemoglobin.

CONCLUSIONS

Infants with NEC have significantly lower cerebral tissue oxygenation throughout their neonatal intensive care stay in comparison with those who did not develop NEC. This is a novel finding and could explain their worse neurodevelopmental outcome.

Burden of hypoxia and intraventricular haemorrhage in extremely preterm infants

OBJECTIVE

Thresholds of cerebral hypoxia through monitoring of near-infrared spectroscopy tissue oxygenation index (TOI) were used to investigate the relationship between intraventricular haemorrhage (IVH) and indices of hypoxia.

DESIGN

Prospective observational study.

SETTING

A single-centre neonatal intensive care unit.

PATIENTS

Infants <28 weeks' gestation with an umbilical artery catheter.

METHODS

Thresholds of hypoxia were determined from mean values of TOI using sequential Χ² tests and used alongside thresholds from existing literature to calculate percentage of time in hypoxia and burden of hypoxia below each threshold. These indices were then compared between IVH groups.

RESULTS

44 infants were studied for a median of 18.5 (range 6-21) hours in the first 24 hours of life. Sequential Χ² analysis yielded a TOI threshold of 71% to differentiate between IVH (16 infants) and no IVH (28 infants). Percentage of time in hypoxia was significantly higher in infants with IVH than those without, using thresholds of 60%-67%. Burden of hypoxia was significantly higher in infants with IVH than without, using thresholds of 62%-80%. With the threshold of 71%, percentage of time in hypoxia was lower by 12.2% with a 95% CI of (-25.7 to 1.2) (p=0.073), and the burden of hypoxia was lower by 29.2% hour (%h) (95% CI -55.2 to -3.1)%h (p=0.012) in infants without IVH than those with IVH.

CONCLUSIONS

Using defined TOI thresholds, infants with IVH spent higher percentage of time in hypoxia with higher burden of cerebral hypoxia than those without, in the first 24 hours of life.

Effect of hyperextension of the neck (rose position) on cerebral blood oxygenation in patients who underwent cleft palate reconstructive surgery: prospective cohort study using near-infrared spectroscopy

OBJECTIVES

To facilitate the best approach during cleft palate surgery, children are positioned with hyperextension of the neck. Extensive head extension may induce intraoperative cerebral ischemia if collateral flow is insufficient. To evaluate and monitor the effect of cerebral blood flow on cerebral tissue oxygenation, near-infrared spectroscopy has proved to be a valuable method. The aim of this study was to evaluate and quantify whether hyperextension affects the cerebral tissue oxygenation in children during cleft palate surgery.

MATERIALS AND METHODS

This prospective study included children (ASA 1 and 2) under the age of 3 years old who underwent cleft palate repair at the Wilhelmina Children's Hospital, in The Netherlands. Data were collected for date of birth, cleft type, date of cleft repair, and physiological parameters (MAP, saturation, heart rate, expiratory CO₂ and O₂, temperature, and cerebral blood oxygenation) during surgery. The cerebral blood oxygenation was measured with NIRS.

RESULTS

Thirty-four children were included in this study. The majority of the population was male (61.8%, n = 21). The mixed model analyses showed a significant drop at time of Rose position of - 4.25 (69-74 95% CI; p < 0.001) and - 4.39 (69-74 95% CI; p < 0.001). Postoperatively, none of the children displayed any neurological disturbance.

CONCLUSION

This study suggests that hyperextension of the head during cleft palate surgery leads to a significant decrease in cerebral oxygenation. Severe cerebral desaturation events during surgery were uncommon and do not seem to be of clinical relevance in ASA 1 and 2 children.

CLINICAL RELEVANCE

There was a significant drop in cerebral oxygenation after positioning however it is not clear whether this drop is truly significant physiologically in ASA 1 and 2 patients.

Near-Infrared Spectroscopy in Pediatric Congenital Heart Disease

Near-infrared spectroscopy (NIRS) is widely used to monitor tissue oxygenation in the pediatric cardiac surgical population. Clinicians who use NIRS must understand the underlying measurement principles in order to interpret and use this monitoring modality appropriately. The aims of this narrative review are to provide a brief overview of NIRS technology, discuss the normative and critical values of cerebral and somatic tissue oxygen saturation and the interpretation of these values, present the clinical studies (and their limitations) of NIRS as a perioperative monitoring modality in the pediatric congenital heart disease population, and introduce the emerging and future applications of NIRS.

Monitoring and management of brain hemodynamics and oxygenation

While cardiorespiratory monitoring is standard for newborns in the NICU, monitoring of brain hemodynamics and oxygenation is usually sporadic and targeted to newborns with suspected or confirmed neurologic disorders. This is unfortunate, since critically ill newborns, both preterm and term-born, are at high risk of brain injury and would benefit from improved techniques for continuous monitoring of brain hemodynamics and oxygenation, in addition to monitoring of systemic hemodynamics and oxygenation. Near-infrared spectroscopy (NIRS) and, to a lesser extent, Doppler ultrasound are techniques that have been used in research and increasingly for clinical purposes to measure and monitor brain hemodynamics and oxygenation in newborns. NIRS monitoring can be useful for detection of diverse pathologic conditions that occur frequently in very preterm newborns and in selected populations of term newborns at risk for brain injury related to disturbances of systemic hemodynamics. This chapter reviews the current state of the art with regard to brain-monitoring techniques and the research directed at this important area, and it concludes with suggestions for the use of currently available tools to manage newborns at high risk of neurologic injury from disturbances in brain hemodynamics and oxygenation.

NIRS improves hemodynamic monitoring and detection of risk for cerebral injury: cases in the neonatal intensive care nursery

Near-infrared spectroscopy (NIRS) monitoring provides a noninvasive, bedside measure of cerebral and somatic oxygenation in neonates at risk for hemodynamic instability and brain injury. This technology has been increasingly utilized in the neonatal intensive care unit, however, clinicians perceive a lack of evidence for the added value of NIRS monitoring. We present six clinical scenarios illustrating the value of NIRS monitoring for the diagnosis and management of critically ill newborns.

Monitoring cerebral oxygenation of the immature brain: a neuroprotective strategy?

Monitoring of cerebral oxygenation (rScO₂) with near-infrared spectroscopy (NIRS) is a feasible noninvasive bedside technique in the NICU. This review discusses the possible neuroprotective role of "pattern recognition" of NIRS-derived rScO₂ in preterm neonates with regard to the prevention of severe intraventricular hemorrhage and hypoxia/hyperoxia-related white matter injury. This neuroprotective role of rScO₂ monitoring is discussed as a modality to aid in the early detection of cerebral oxygenation conditions predisposing to these complications. Practical guidelines are provided concerning management of abnormal rScO₂ patterns as well as a brief discussion concerning the need for international consensus and the legal aspects associated with the introduction of a new NICU bedside monitoring strategy.

Prospective observational study on assessing the hemodynamic relevance of patent ductus arteriosus with frequency domain near-infrared spectroscopy

BACKGROUND

What constitutes a hemodynamically relevant patent ductus arteriosus (hrPDA) in preterm infants is unclear. Different clinical and echocardiographic parameters are used, but a gold standard definition is lacking. Our objective was to evaluate associations between regional cerebral tissue oxygen saturation (rcStO₂), fraction of tissue oxygen extraction (rcFtO₂E) measured by frequency domain near-infrared spectroscopy (fd-NIRS) and their correlation to echocardiographic, Doppler-ultrasound, and clinical parameters in preterm infants with and without a hrPDA.

METHODS

In this prospective observational study, 22 infants < 1500 g (mean [± SD]: gestational age 28.6 [±1.8] weeks, birth weight 1076 [±284] g, median (interquartile range) postnatal age at measurement 7.6 (4.6-12.9) d) with a clinical suspicion of hrPDA were analysed. Twelve infants had left-to-right shunt through PDA, and in 6 of these the PDA was classified as hrPDA based on pre-defined clinical and echocardiographic criteria. fd-NIRS, echocardiographic and Doppler-ultrasound examinations were performed. After identification of blood hemoglobin (Hb) as confounding factor, rcStO₂ and rcFtO₂E were corrected for this effect.

RESULTS

Overall mean ± standard deviation (normalised to a median Hb of 13.8 mg/dl) was 57 ±5% for rcStO₂ and 0.39 ±0.05 for rcFtO₂E. Comparing no-hrPDA with hrPDA infants, there were no significant differences in mean rcStO₂ (58 ±5% vs. 54 ±5%; p = .102), but in mean rcFtO₂E (0.38 ±0.05 vs. 0.43 ±0.05; p = .038). Echocardiographic parameter and Doppler indices did not correlate with cerebral oxygenation.

CONCLUSION

Oxygen transport capacity of the blood may confound NIRS data interpretation. Cerebral oxygenation determined by fd-NIRS provided additional information for PDA treatment decisions not offered by routine investigations. Whether indicating PDA therapy based on echocardiography complemented by data on cerebral oxygenation results in better outcomes should be investigated in future studies.

End-Organ Saturation Differences in Early Neonatal Transition for Left- versus Right-Sided Congenital Heart Disease

BACKGROUND

For neonates with congenital heart disease (CHD), left-sided (LL) and right-sided (RL) single ventricular physiologies (LL, hypoplastic left heart syndrome; RL, tricuspid atresia or pulmonary atresia with intact ventricular septum) may demonstrate distinct changes in tissue saturation in the first 72 h of life. Near-infrared spectroscopy (NIRS) can measure regional cerebral saturation (Csat) and renal saturation (Rsat) to clarify differences between LL and RL over time.

OBJECTIVES

Our primary objective was to measure changes in Csat and Rsat in the first 72 h of life using NIRS between CHD infants with LL compared to RL. The secondary objective was to correlate NIRS values to an echocardiographic marker of perfusion.

METHOD

Newborns with hypoplastic left heart syndrome, tricuspid atresia, and pulmonary atresia with intact ventricular septum from 2013 to 2016 underwent routine NIRS monitoring. Csat, Rsat, and systemic saturations (SpO2) in the first 72 h of life were retrospectively analyzed and the echocardiographic descending aorta velocity time integral (VTI) was measured. Mixed effects models compared differences over time between LL and RL.

RESULTS

The final cohort included 13 LL, 12 RL, and 4 controls. Csat decreased for RL compared to LL (p = 0.005), while Rsat decreased for both (p = 0.008). Over time, SpO2 increased for LL but decreased for RL (p = 0.046). Compared to the controls, infants with CHD had lower Csat, lower Rsat, and lower SpO2. The descending aorta VTI was correlated with Rsat (R2 = 0.24, p = 0.02).

CONCLUSION

NIRS Csat measures were better preserved in LL compared to RL. Rsat decreased in both groups through time. The correlation between the descending aorta VTI and Rsat suggests an association between NIRS measures of renal saturation and renal perfusion.

Cerebral near-infrared spectroscopy monitoring for prevention of brain injury in very preterm infants

BACKGROUND

Cerebral injury and long-term neurodevelopmental impairment is common in extremely preterm infants. Cerebral near-infrared spectroscopy (NIRS) enables continuous estimation of cerebral oxygenation. This diagnostic method coupled with appropriate interventions if NIRS is out of normal range (that is cerebral oxygenation within the 55% to 85% range) may offer benefits without causing more harms. Therefore, NIRS coupled with appropriate responses to abnormal findings on NIRS needs assessment in a systematic review of randomised clinical trials and quasi-randomised studies.

OBJECTIVES

To evaluate the benefits and harms of interventions that attempt to alter cerebral oxygenation guided by cerebral NIRS monitoring in order to prevent cerebral injury, improve neurological outcome, and increase survival in preterm infants born more than 8 weeks preterm.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 8), MEDLINE via PubMed (1966 to 10 September 2016), Embase (1980 to 10 September 2016), and CINAHL (1982 to 10 September 2016). We also searched clinical trial databases, conference proceedings, and the reference lists of retrieved articles for randomised clinical trials and quasi-randomised studies.

SELECTION CRITERIA

Randomised clinical trials and quasi-randomised clinical studies comparing continuous cerebral NIRS monitoring for at least 24 hours versus blinded NIRS or versus no NIRS monitoring.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected, assessed the quality of, and extracted data from the included trials and studies. If necessary, we contacted authors for further information. We conducted assessments of risks of bias; risks of design errors; and controlled the risks of random errors with Trial Sequential Analysis. We assessed the quality of the evidence with GRADE.

MAIN RESULTS

One randomised clinical trial met inclusion criteria, including infants born more than 12 weeks preterm. The trial employed adequate methodologies and was assessed at low risk of bias. One hundred and sixty-six infants were randomised to start continuous cerebral NIRS monitoring less than 3 hours after birth until 72 hours after birth plus appropriate interventions if NIRS was out of normal range according to a guideline versus conventional monitoring with blinded NIRS. There was no effect of NIRS plus guideline of mortality until term-equivalent age (RR 0.50, 95% CI 0.29 to 1.00; one trial; 166 participants). There were no effects of NIRS plus guideline on intraventricular haemorrhages: all grades (RR 0.93, 95% CI 0.65 to 1.34; one trial; 166 participants); grade III/IV (RR 0.57, 95% CI 0.25 to 1.31; one trial; 166 participants); and cystic periventricular leukomalacia (which did not occur in either group). Likewise, there was no effect of NIRS plus guideline on the occurrence of a patent ductus arteriosus (RR 1.96, 95% CI 0.94 to 4.08; one trial; 166 participants); chronic lung disease (RR 1.27, 95% CI 0.94 to 1.50; one trial; 166 participants); necrotising enterocolitis (RR 0.83, 95% CI 0.33 to 1.94; one trial; 166 participants); and retinopathy of prematurity (RR 1.64, 95% CI 0.75 to 3.00; one trial; 166 participants). There were no serious adverse events in any of the intervention groups. NIRS plus guideline caused more skin marks from the NIRS sensor in the control group than in the experimental group (unadjusted RR 0.31, 95% CI 0.10 to 0.92; one trial; 166 participants). There are no data regarding neurodevelopmental outcome, renal impairment or air leaks.The quality of evidence for all comparisons discussed above was assessed as very low apart from all-cause mortality and adverse events: these were assessed as low and moderate, respectively. The validity of all comparisons is hampered by a small sample of randomised infants, risk of bias due to lack of blinding, and indirectness of outcomes.

AUTHORS' CONCLUSIONS

The only eligible randomised clinical trial did not demonstrate any consistent effects of NIRS plus a guideline on the assessed clinical outcomes. The trial was, however, only powered to detect difference in cerebral oxygenation, not morbidities or mortality. Our systematic review did not reach sufficient power to prove or disprove effects on clinical outcomes. Further randomised clinical trials with low risks of bias and low risks of random errors are needed.

Neonatal Hypoxia Ischaemia: Mechanisms, Models, and Therapeutic Challenges

Neonatal hypoxia-ischaemia (HI) is the most common cause of death and disability in human neonates, and is often associated with persistent motor, sensory, and cognitive impairment. Improved intensive care technology has increased survival without preventing neurological disorder, increasing morbidity throughout the adult population. Early preventative or neuroprotective interventions have the potential to rescue brain development in neonates, yet only one therapeutic intervention is currently licensed for use in developed countries. Recent investigations of the transient cortical layer known as subplate, especially regarding subplate's secretory role, opens up a novel set of potential molecular modulators of neonatal HI injury. This review examines the biological mechanisms of human neonatal HI, discusses evidence for the relevance of subplate-secreted molecules to this condition, and evaluates available animal models. Neuroserpin, a neuronally released neuroprotective factor, is discussed as a case study for developing new potential pharmacological interventions for use post-ischaemic injury.

Early biomarkers of brain injury and cerebral hypo- and hyperoxia in the SafeBoosC II trial

BACKGROUND

The randomized clinical trial, SafeBoosC II, examined the effect of monitoring of cerebral oxygenation by near-infrared spectroscopy combined with a guideline on treatment when cerebral oxygenation was out of the target range. Data on cerebral oxygenation was collected in both the intervention and the control group. The primary outcome was the reduction in the burden of cerebral hypo- and hyperoxia between the two groups. In this study we describe the associations between the burden of cerebral hypo- and hyperoxia, regardless of allocation to intervention or control group, and the biomarkers of brain injury from birth till term equivalent age that was collected as secondary and explorative outcomes in the SafeBoosC II trial.

METHODS

Cerebral oxygenation was continuously monitored during the first 72h of life in 166 extremely preterm infants. Cranial ultrasound was performed at day 1,4,7,14, and 35 and at term. Electroencephalogram (EEG) was recorded at 64h. Blood-samples taken at 6 and 64 hours were analysed for the brain injury biomarkers; S100beta, brain-fatty-acid-binding-protein, and neuroketal. All analyses were conducted post hoc.

RESULTS

Significantly more infants with a cerebral burden of hypoxia within the 4th quartile versus infants within quartile 1-3 were diagnosed with severe intracranial haemorrhage (11/39 versus 11/117, p = 0.003), had low burst rate on EEG (12/28 versus 21/103, p = 0.015), or died (14/41 versus 18/123, p = 0.006), whereas none of these events were significantly associated with cerebral hyperoxia. The blood biomarkers were not significantly associated with the burden of cerebral hypo- or hyperoxia.

CONCLUSIONS

The explorative analysis showed that early burden of cerebral hypoxia, but not hyperoxia was significantly associated with low brain electrical activity and severe intracranial haemorrhage while none of the three blood biomarkers were associated with the burden of either cerebral hypo- or hyperoxia.

Monitoring Cerebral Oxygenation in Neonates: An Update

Cerebral oxygenation is not always reflected by systemic arterial oxygenation. Therefore, regional cerebral oxygen saturation (rScO₂) monitoring with near-infrared spectroscopy (NIRS) is of added value in neonatal intensive care. rScO₂ represents oxygen supply to the brain, while cerebral fractional tissue oxygen extraction, which is the ratio between rScO₂ and systemic arterial oxygen saturation, reflects cerebral oxygen utilization. The balance between oxygen supply and utilization provides insight in neonatal cerebral (patho-)physiology. This review highlights the potential and limitations of cerebral oxygenation monitoring with NIRS in the neonatal intensive care unit.

Cerebral oxygenation and echocardiographic parameters in preterm neonates with a patent ductus arteriosus: an observational study

BACKGROUND

A haemodynamically significant patent ductus arteriosus (hsPDA) is clinically suspected and confirmed by echocardiographic examination. A hsPDA decreases cerebral blood flow and oxygen saturation by the ductal steal phenomenon.

AIM

To determine the relationship between echocardiographic parameters, cerebral oxygenation and a hsPDA in preterm infants.

METHODS

380 preterm infants (<32 weeks gestational age) born between 2008 and 2010 were included. Blinded echocardiographic examination was performed on the second, fourth and sixth day after birth. Examinations were deblinded when hsPDA was clinically suspected. Regional cerebral oxygen saturation (rScO₂) was continuously monitored by near-infrared spectroscopy during 72 h after birth, and afterwards for at least 1 h before echocardiography. Echocardiographic parameters included ductal diameter, end-diastolic flow in the left pulmonary artery, left atrium/aorta ratio and ductal flow pattern.

RESULTS

rScO₂ was significantly related only to ductal diameter over time. Mixed modelling analysed the course of rScO₂ over time, where infants were divided into four groups: a closed duct, an open haemodynamically insignificant duct (non-sPDA), a hsPDA, which was successfully closed during study period (SC hsPDA) or a hsPDA, which was unsuccessfully closed during study period (UC hsPDA). SC hsPDA infants showed the highest rScO₂ on day 6, while UC hsPDA infants had the lowest rScO₂ values.

CONCLUSIONS

Ductal diameter is the only echocardiographic parameter significantly related to cerebral oxygenation over time. Cerebral oxygenation takes a different course over time depending on the status of the duct. Low cerebral oxygenation may be suggestive of a hsPDA.

Near-infrared spectroscopy for detection of a significant patent ductus arteriosus

BACKGROUND

Near-infrared spectroscopy (NIRS) may assist with characterization of a hemodynamically significant patent ductus arteriosus (hsPDA) by measuring cerebral and renal saturation (Csat and Rsat) levels. We hypothesized that Csat and Rsat in preterm infants with an hsPDA would be decreased compared to those with no PDA or nonsignificant PDA.

METHODS

This non a-priori designed study retrospectively investigated clinical and ECHO characteristics of preterm infants <29 wk gestation who underwent routine NIRS monitoring. Logistic regression assessed association between NIRS measures and an hsPDA by ECHO.

RESULTS

Of 47 infants, 21 had a confirmed hsPDA by ECHO, 14 had a nonsignificant PDA, and 12 had no ECHO performed due to low clinical suspicion for PDA. Logistic regression adjusted for gestational age found that lower Rsat was associated with an hsPDA by ECHO (OR 0.9, 95% CI 0.83-0.98, P = 0.01). Using ROC curves, Rsat < 66% identified an hsPDA with a sensitivity of 81% and specificity of 77%, while Csat was not significant.

CONCLUSION

Low Rsat < 66% was associated with the presence of an hsPDA in the preterm infant. Csat may be preserved if cerebral autoregulation is largely intact. Bedside NIRS monitoring may reasonably increase suspicion for a significant PDA in the preterm infant.

Mechanical Ventilation during Acute Brain-Injury in Children

Mechanical ventilation in the brain-injured pediatric patient requires many considerations, including the type and severity of lung and brain injury and how progression of such injury will develop. This review focuses on neurological breathing patterns at presentation, the effect of brain injury on the lung, developmental aspects of blood gas tensions on cerebral blood flow, and strategies used during mechanical ventilation in infants and children receiving neurological intensive care. Taking these basic principles, our clinical approach is informed by balancing the blood gas tension targets that follow from the ventilation support we choose and the intracranial consequences of these choices on vascular and hydrodynamic physiology. As such, we are left with two key decisions: a low tidal volume strategy for the lung versus the consequence of hypercapnia on the brain; and the use of positive end expiratory pressure to optimize oxygenation versus the consequence of impaired cerebral venous return from the brain and resultant intracranial hypertension.

Cardiopulmonary Interactions

OBJECTIVES

The objectives of this review are to discuss the mechanisms by which respiration impacts cardiovascular function and vice versa, with an emphasis on the impact of these interactions in pediatric cardiac critical care.

DATA SOURCE

A search of MEDLINE was conducted using PubMed.

CONCLUSIONS

In the presence of underlying cardiac and respiratory disease, the interplay between these two systems is significant and plays a pivotal role in the pathophysiology of acute and chronic phases of a wide spectrum of diseases. An understanding of these relationships is essential to optimizing the care of critically ill patients.

Hemodynamic Monitoring

OBJECTIVES

In this review, we discuss hemodynamic monitoring modalities, including their application, the interpretation of data, limitations, and impact on outcomes.

DATA SOURCE

MEDLINE, PubMed.

CONCLUSIONS

One of the tenets of critical care medicine is to ensure adequate tissue oxygenation. This assessment must be timely and accurate to optimize outcomes. The clinical assessment of cardiac function, cardiac output, and tissue oxygenation based on the physical examination and standard hemodynamic variables, although an indispensable part of this exercise, has significant limitations. The use of adjunctive hemodynamic monitoring modalities provides a much more objective, accurate, and timely assessment of the patient's hemodynamic profile and is invaluable for assessing the patient's clinical status, clinical trajectory, and response to interventions.

Cerebral oximetry in preterm infants: an agenda for research with a clear clinical goal

Preterm birth constitutes a major cause of death before 5 years of age and it is a major cause of neurodevelopmental impairment across the world. Preterm infants are most unstable during the transition between fetal and newborn life during the first days of life and most brain damage occurs in this period. The brain of the preterm infant is accessible for tissue oximetry by near-infrared spectroscopy. Cerebral oximetry has the potential to improve the long-term outcome by helping to tailor the support of respiration and circulation to the individual infant's needs, but the evidence is still lacking. The goals for research include testing the benefit and harms of cerebral oximetry in large-scale randomized trials, improved definition of the hypoxic threshold, better understanding the effects of intensive care on cerebral oxygenation, as well as improved precision of oximeters and calibration among devices or standardization of values in the hypoxic range. These goals can be pursued in parallel.

The SafeBoosC II randomized trial: treatment guided by near-infrared spectroscopy reduces cerebral hypoxia without changing early biomarkers of brain injury

BACKGROUND

The SafeBoosC phase II multicentre randomized clinical trial investigated the benefits and harms of monitoring cerebral oxygenation by near-infrared spectroscopy (NIRS) combined with an evidence-based treatment guideline vs. no NIRS data and treatment as usual in the control group during the first 72 h of life. The trial demonstrated a significant reduction in the burden of cerebral hypoxia in the experimental group. We now report the blindly assessed and analyzed treatment effects on electroencephalographic (EEG) outcomes (burst rate and spectral edge frequency 95% (SEF95)) and blood biomarkers of brain injury (S100β, brain fatty acid-binding protein, and neuroketal).

METHODS

One hundred and sixty-six extremely preterm infants were randomized to either experimental or control group. EEG was recorded at 64 h of age and blood samples were collected at 6 and 64 h of age.

RESULTS

One hundred and thirty-three EEGs were evaluated. The two groups did not differ regarding burst rates (experimental 7.2 vs. control 7.7 burst/min) or SEF95 (experimental 18.1 vs. control 18.0 Hz). The two groups did not differ regarding blood S100β, brain fatty acid-binding protein, and neuroketal concentrations at 6 and 64 h (n = 123 participants).

CONCLUSION

Treatment guided by NIRS reduced the cerebral burden of hypoxia without affecting EEG or the selected blood biomarkers.

Patent Ductus Arteriosus and Brain Volume

BACKGROUND AND OBJECTIVES

A hemodynamically significant patent ductus arteriosus (PDA) can compromise perfusion and oxygenation of the preterm brain. Reports suggest that PDA is associated with increased mortality and morbidity. We hypothesize that long-standing low cerebral oxygenation due to PDA might affect brain volume at term equivalent age.

METHODS

Observational study in 140 infants investigating the relationship between near-infrared spectroscopy-monitored cerebral oxygen saturation (rSco2) and MRI-assessed regional brain volume and maturation of the posterior limb of the internal capsule at term-equivalent age in 3 groups: those whose PDA closed with indomethacin, those who needed additional surgical closure, and matched controls.

RESULTS

The surgery group had the lowest rSco2 values before closure (n = 35), 48% ± 9.7% (mean ± SD) as compared with the indomethacin (n = 35), 59% ± 10.4 (P < .001), and control groups (n = 70), 66% ± 6.9 (P < .001); the highest postnatal age before effective treatment; and the lowest volumes of most brain regions at term-equivalent age. Multiple linear regression analysis showed a significant effect of preductal closure rSco2 on cerebellar volume in this group. No differences were found in maturation of the posterior limb of the internal capsule.

CONCLUSIONS

Long-standing suboptimal cerebral oxygenation due to a PDA may negatively influence brain growth, affecting neurodevelopmental outcome.

Reference values of regional cerebral oxygen saturation during the first 3 days of life in preterm neonates

BACKGROUND

Currently, reliable reference values of regional cerebral oxygen saturation (rScO2) for different gestational age (GA) groups are lacking, which hampers the implementation of near-infrared spectroscopy (NIRS) alongside monitoring arterial oxygen saturation (SaO2) and blood pressure in neonatal intensive care. The aim of this study was to provide reference values for rScO2 and cerebral fractional tissue oxygen extraction (cFTOE; (SaO2 - rScO2)/SaO2) for small adult and neonatal NIRS sensors.

METHODS

In this study, 999 infants born preterm (GA <32 wk) were monitored with NIRS during the first 72 h of life. Mixed modeling was used to generate reference curves grouped per 2 wk of GA. In addition, the influence of a hemodynamically significant patent ductus arteriosus, gender, and birth weight were explored.

RESULTS

Average rScO2 was ~65% at admission, increased with GA (1% per week) and followed a parabolic curve in relation to postnatal age with a peak at ~36 h. The cFTOE showed similar but inverse effects. On average, the neonatal sensor measured 10% higher than the adult sensor.

CONCLUSION

rScO2 and cFTOE reference curves are provided for the first 72 h of life in preterm infants, which might support the broader implementation of NIRS in neonatal intensive care.

Effects of Fractional Inspired Oxygen on Cerebral Oxygenation in Preterm Infants following Delivery

OBJECTIVES

To explore regional cerebral oxygen saturations (rcSO2) in preterm neonates initially stabilized with 0.3 fractionated inspired oxygen (FiO2) concentrations. We hypothesized that those infants who received >0.3 FiO2 during stabilization following delivery would have relatively higher rcSO2 postdelivery compared with those stabilized with a lower FiO2.

STUDY DESIGN

A single center prospective observational study of 47 infants born before 32 weeks. Using near infrared spectroscopy, rcSO2 values were recorded immediately after birth. All preterm infants were initially given 0.3 FiO2 and were divided into 2 groups according to subsequent FiO2 requirements of either ≤0.3 or >0.3 FiO2. Using a mixed-effects model, we compared the difference between the groups over time. Also, the area measures below 55% (hypoxia) and above 85% (hyperoxia) were compared between the groups.

RESULTS

The mean (SD) gestation was 29.4 (1.6) weeks and the mean (SD) weight was 1.3 (0.4) kg. Less than one-half of the infants (20/45; 43%) required ≤0.3 FiO2. In the delivery suite, the median (IQR) rcSO2 in the low and high FiO2 groups were 81% (66%-86%) and 72% (62%-86%), respectively. Patients in the high FiO2 group had a larger rcSO2 area below 55% (P = .01). There was a significant difference in rcSO2 between the groups (P < .05), with the low group having higher rcSO2 values initially, but this difference changed over time. In the neonatal intensive care unit (NICU), rcSO2 values were lower by 7.1% (CI 12.13 to 2.06%) P = .008 in the high FiO2 group.

CONCLUSIONS

Infants given >0.3 FiO2 had more cerebral hypoxia than infants requiring ≤0.3 FiO2 but no difference in the degree of cerebral hyperoxia, both in the delivery suite and the NICU. This suggests that a more rapid increase in oxygen titration maybe be required initially for preterm infants.

Neonatal brain oxygenation during thoracoscopic correction of esophageal atresia

Background

Little is known about the effects of carbon dioxide (CO₂) insufflation on cerebral oxygenation during thoracoscopy in neonates. Near-infrared spectroscopy can measure perioperative brain oxygenation [regional cerebral oxygen saturation (rScO₂)].

Aims

To evaluate the effects of CO₂ insufflation on rScO₂ during thoracoscopic esophageal atresia (EA) repair.

Methods

This is an observational study during thoracoscopic EA repair with 5 mmHg CO₂ insufflation pressure. Mean arterial blood pressure (MABP), arterial oxygen saturation (SaO₂), partial pressure of arterial carbon dioxide (paCO₂), pH, and rScO₂ were monitored in 15 neonates at seven time points: baseline (T0), after anesthesia induction (T1), after CO₂-insufflation (T2), before CO₂-exsufflation (T3), and postoperatively at 6 (T4), 12 (T5), and 24 h (T6).

Results

MABP remained stable. SaO₂ decreased from T0 to T2 [97 ± 3–90 ± 6 % (p < 0.01)]. PaCO₂ increased from T0 to T2 [41 ± 6–54 ± 15 mmHg (p < 0.01)]. pH decreased from T0 to T2 [7.33 ± 0.04–7.25 ± 0.11 (p < 0.05)]. All parameters recovered during the surgical course. Mean rScO₂ was significantly higher at T1 compared to T2 [77 ± 10–73 ± 7 % (p < 0.05)]. Mean rScO₂ levels never dropped below a safety threshold of 55 %.

Conclusion

The impact of neonatal thoracoscopic repair of EA with insufflation of CO₂ at 5 mmHg was studied. Intrathoracic CO₂ insufflation caused a reversible decrease in SaO₂ and pH and an increase in paCO₂. The rScO₂ was higher at anesthesia induction but remained stable and within normal limits during and after the CO₂ pneumothorax, which suggest no hampering of cerebral oxygenation by the thoracoscopic intervention. Future studies will focus on the long-term effects of this surgery on the developing brain.

Cerebral oxygenation is associated with neurodevelopmental outcome of preterm children at age 2 to 3 years

AIM

The aim of the study was to determine whether regional cerebral tissue oxygen saturation (r(c)SO2) and fractional tissue oxygen extraction (FTOE), using near-infrared spectroscopy, are associated with neurodevelopmental outcome of preterm infants.

METHOD

We measured rc SO2 on days 1, 2, 3, 4, 5, 8, and 15 after birth in 83 preterm infants (<32wks gestational age), and calculated FTOE=(SpO2 -r(c)SO2)/SpO2. Cognitive, motor, neurological, and behavioural outcomes were determined at 2 to 3 years using the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III), an age-specific neurological examination, and the Child Behavior Checklist (CBCL) respectively. Multiple linear regression analyses were used to determine whether r(c)SO2 and FTOE contributed to outcome.

RESULTS

We followed up 67 infants. The lower quartile (P(25-50)) and highest quartile (P(75-100)) of r(c)SO2 on day 1 were associated with poorer cognitive outcome (p=0.044 and p=0.008 respectively). A lower area under the curve (AUC; over 15d) of r(c)SO2 was associated with poorer cognitive outcome (p=0.014). The lower quartile (P(25-50)) AUC of r(c)SO2 was associated with poorer fine motor outcome (p=0.004). The amount of time r(c)SO2 <50% on day 1 was negatively associated with gross motor outcome (p=0.002). The highest quartile of FTOE on day 1 was associated with poorer total motor outcome (p=0.041).

INTERPRETATION

Cerebral oxygen saturation during the first 2 weeks after birth is associated with neurodevelopmental outcome of preterm infants at 2 to 3 years. High and low r(c)SO2 on day 1 were associated with poorer neurodevelopmental outcome.

Cerebrovascular control is altered in healthy term infants when they sleep prone

STUDY OBJECTIVES

Sudden infant death syndrome (SIDS) is a leading cause of infant death, and prone sleeping is the major risk factor. Prone sleeping impairs arousal from sleep and cardiovascular control in infants at 2-3 months, coinciding with the highest risk period for SIDS. We hypothesized that prone sleeping would also alter cerebrovascular control, and aimed to test this hypothesis by examining responses of cerebral oxygenation to head-up tilts (HUTs) over the first 6 months after birth.

STUDY DESIGN AND PARTICIPANTS

Seventeen healthy full-term infants were studied at 2-4 weeks, 2-3 months, and 5-6 months of age using daytime polysomnography, with the additional measurements of blood pressure (BP, Finometer™, Finometer Medical Systems, The Netherlands) and cerebral tissue oxygenation index (TOI, NIRO 200, Hamamatsu Photonics KK, Japan). HUTs were performed in active sleep (AS) and quiet sleep (QS) in both prone and supine positions.

RESULTS

When infants slept in the prone position, a sustained increase in TOI (P < 0.05) occurred following HUTs, except in QS at 2-3 months when TOI was unchanged. BP was either unchanged or fell below baseline during the sustained TOI increase, signifying cerebro-vasodilatation. In contrast, when infants slept supine, TOI did not change after HUTs, except in QS at 2-3 and 5-6 months when TOI dropped below baseline (P < 0.05).

CONCLUSIONS

When infants slept in the prone position, cerebral arterial vasodilation and increased cerebral oxygenation occurred during head-up tilts, possibly as a protection against cerebral hypoxia. Absence of the vasodilatory response during quiet sleep at 2-3 months possibly underpins the decreased arousability from sleep and increased risk for sudden infant death syndrome at this age.

Brain vascular and hydrodynamic physiology

Protecting the brain in vulnerable infants undergoing surgery is a central aspect of perioperative care. Understanding the link between blood flow, oxygen delivery, and oxygen consumption leads to a more informed approach to bedside care. In some cases, we need to consider how high we can let the partial pressure of carbon dioxide go before we have concerns about risk of increased cerebral blood volume and change in intracranial hydrodynamics. Alternatively, in almost all such cases, we have to address the question of how low can we let the blood pressure drop before we should be concerned about brain perfusion. This review provides a basic understanding of brain bioenergetics, hemodynamics, hydrodynamics, autoregulation, and vascular homeostasis to changes in blood gases, which is fundamental to our thinking about bedside care and monitoring.

Comparing near-infrared spectroscopy devices and their sensors for monitoring regional cerebral oxygen saturation in the neonate

BACKGROUND

Near-infrared spectroscopy (NIRS) is an upcoming clinical method for monitoring regional cerebral oxygen saturation (rScO2) in neonates. There is a growing market offering different devices and sensors. Even though this technique is increasingly clinically applied, little is known about the similarities and/or differences in rScO2 values between the different devices and sensors. The aim of this study was to compare the rScO2 values obtained in (preterm) neonates with all available sensors of three frequently used NIRS devices.

METHODS

Fifty-five neonates admitted to our neonatal intensive care unit (NICU) were included in this study. rScO2 was simultaneously monitored bilaterally with two different NIRS sensors (left and right frontoparietal) for at least 1 h. Then, the sensors were switched, and measurements were collected for at least another hour.

RESULTS

We detected a rather close correlation between all investigated sensors from the three different NIRS devices, but absolute rScO2 values showed substantial differences: Bland-Altman analysis showed average differences from 10 to 15%.

CONCLUSION

Although the rScO2 values correlated well between different NIRS sensors, sometimes there were substantial differences between the absolute rScO2 values, which may complicate clinical application.

Monitoring tissue perfusion, oxygenation, and metabolism in critically ill patients

Alterations in oxygen transport and use are integral to the development of multiple organ failure; therefore, the ultimate goal of resuscitation is to restore effective tissue oxygenation and cellular metabolism. Hemodynamic monitoring is the cornerstone of management to promptly identify and appropriately manage (impending) organ dysfunction. Prospective randomized trials have confirmed outcome benefit when preemptive or early treatment is directed toward maintaining or restoring adequate tissue perfusion. However, treatment end points remain controversial, in large part because of current difficulties in determining what constitutes "optimal." Information gained from global whole-body monitoring may not detect regional organ perfusion abnormalities until they are well advanced. Conversely, the ideal "canary" organ that is readily accessible for monitoring, yet offers an early and sensitive indicator of tissue "unwellness," remains to be firmly identified. This review describes techniques available for real-time monitoring of tissue perfusion and metabolism and highlights novel developments that may complement or even supersede current tools.

Metabolic regulatory clues from the naked mole rat: toward brain regulatory functions during stroke

Resistance to tissue hypoxia is a robust fundamental adaptation to low oxygen supply, and represents a novel neuroscience problem with significance to mammalian physiology as well as human health. With the underlying mechanisms strongly conserved in evolution, the ability to resist tissue hypoxia in natural systems has recently emerged as an interesting model in mammalian physiology research to understand mechanisms that can be manipulated for the clinical management of stroke. The extraordinary ability to resist tissue hypoxia by the naked mole rat (NMR) indicates the presence of a unique mechanism that underlies the remarkable healthy life span and exceptional hypoxia resistance. This opens an interesting line of research into understanding the mechanisms employed by the naked mole rat (Heterocephalus glaber) to protect the brain during hypoxia. In a series of studies, we first examined the presence of neuroprotection in the brain cells of naked mole rats (NMRs) subjected to hypoxic insults, and then characterized the expression of such neuroprotection in a wide range of time intervals. We used oxygen nutrient deprivation (OND), an in vitro model of resistance to tissue hypoxia to determine whether there is evidence of neuronal survival in the hippocampal (CA1) slices of NMRs that are subjected to chronic hypoxia. Hippocampus neurons of NMRs that were kept in hypoxic condition consistently tolerated OND right from the onset time of 5h. This tolerance was maintained for 24h. This finding indicates that there is evidence of resistance to tissue hypoxia by CA1 neurons of NMRs. We further examined the effect of hypoxia on metabolic rate in the NMR. Repeated measurement of metabolic rates during exposure of naked mole rats to hypoxia over a constant ambient temperature indicates that hypoxia significantly decreased metabolic rates in the NMR, suggesting that the observed decline in metabolic rate during hypoxia may contribute to the adaptive mechanism used by the NMR to resist tissue hypoxia. This work is aimed to contribute to the understanding of mechanisms of resistance to tissue hypoxia in the NMR as an important life-sustaining process, which can be translated into therapeutic interventions during stroke.

[Cerebral near-infrared spectroscopy (NIRS) in paediatric anaesthesia]

Cerebral oximetry allows continuous real-time and non-invasive monitoring of cerebral oxygen saturation (cSO(2)), by measuring oxyhaemoglobin and deoxyhaemoglobin near infrared light absorption, similarly to pulse oximetry. cSO(2) measurement predominantly reflects brain venous compartment, and is correlated with jugular venous saturation. As jugular venous saturation, cSO(2) must therefore be interpreted as a measure of balance between transport and consumption of O(2) in the brain. Cerebral oximetry should be used as a trend monitoring, because its accuracy is insufficient to be considered as reliable measure of absolute value of ScO(2). In adult, correction of intraoperative cerebral desaturation reduces hospital stay, heavy morbidity and mortality, and serious postoperative neurocognitive impairment after cardiac and major abdominal surgery. In children, the occurrence of intra- and postoperative cerebral desaturations during congenital heart surgery is associated with increased neurological morbi-mortality. Cerebral oximetry could be a useful monitoring during anaesthesia of (ex) preterm neonates, due to the risk of impaired cerebral blood flow autoregulation in these patients.

Cerebral oxygenation during subclinical seizures in neonatal hypoxic-ischaemic encephalopathy

Treatment of subclinical seizures in newborn HIE remains a contentious issue, especially in light of potential adverse effects of aggressive use of anticonvulsants. We report on the association of subclinical seizures with changes in cerebral oxygenation in an infant with HIE. Our results show that subclinical seizures of longer durations and with associated autonomic disturbance (increased blood pressure) are more likely to be associated with fluctuation in cerebral oxygenation, with some seizures resulting in cerebral hypoxia. Future studies should aim to delineate the effects of subclinical seizure and anticonvulsant treatment on cerebral oxygenation, and their relationships to developmental outcome. Level of cerebral oxygenation may play a role in refining anti-convulsant treatment and management of subclinical seizures in newborns.

The utility of amplitude-integrated EEG and NIRS measurements as indices of hypoxic ischaemia in the newborn pig

OBJECTIVE

The early detection and stratification of potential hypoxic ischaemia (HI) injury in neonates are crucial for reducing the risk of neural disability. This study investigates early changes in brain function caused by acute HI of varying severities in the neonatal pig.

METHODS

Two non-invasive techniques, amplitude-integrated electroencephalogram (aEEG) and near-infrared spectroscopy (NIRS), were used to monitor electrocortical and cerebral haemodynamic function, respectively. The fraction of inspired oxygen (FiO(2)) was varied to produce different HI severities. The sensitivity and HI correlation of these methods were systematically analysed to assess their abilities to both detect injury early and assess HI severity accurately.

RESULTS

The tissue oxygen index measured via NIRS detected acute changes in cerebral oxygenation and was highly sensitive to HI (sensitivity=0.97), whereas aEEG was comparatively insensitive to HI. On the other hand, aEEG measurements correlated well with FiO(2) during the entire HI event as well as the 3-h recovery period (R=0.43-0.61). NIRS measurements did not correlate well with FiO(2).

CONCLUSIONS

Parameters measured via aEEG and NIRS displayed different time profiles during and following the HI event.

SIGNIFICANCE

These results highlight the potential advantage of using aEEG and NIRS in conjunction to monitor neonatal brain function, and provide an objective and rigorous method for the characterisation of cerebral function both during and following HI insults.