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

Body Size, Cerebral Blood Flow, Ambient Temperature, and Relative Brain Temperatures in Newborn Infants under Incubator Care

Subtle changes in body temperature affect the outcomes of ill newborns. However, the temperature profile of neonatal brains remains largely unknown. In open-cot care, increased cerebral perfusion is correlated with higher superficial brain temperatures. This study investigated the dependence of brain temperature (relative to rectal temperature) on ambient temperature, body size, cerebral perfusion, and metabolism in infants receiving incubator care. Rectal, scalp, and brain temperatures, superior vena cava flow, and brain oxygenation were assessed using echocardiography, thermo-compensatory temperature monitoring, and near-infrared spectroscopy in 60 newborns. These infants had a mean postconceptional age of 36.9 (2.2) weeks and weighed 2348 (609) g at the time of evaluation. The ambient temperature was maintained at 30.0 (1.0) °C. A higher rectal temperature was associated with greater postconceptional age (p = 0.002), body weight (p < 0.001), and head circumference (p < 0.001). Relative scalp, superficial brain, and deep brain temperatures were associated with smaller head circumference (p < 0.001, p = 0.030, and p = 0.015, respectively) and superior vena cava flow (p = 0.002, p = 0.003, and p = 0.003, respectively). In infants receiving incubator care, larger head sizes and increased brain perfusion were associated with lower relative scalp and brain temperatures. When considered alongside previous reports, cerebral perfusion may contribute to maintaining stable cerebral tissue temperature against ambient temperature changes.

Intraoperative Regional Cerebral Oxygenation During Pediatric Thoracoscopic Surgery: A Systematic Review

Background: Ventilating a pediatric patient during thoracoscopy is challenging. Few studies have highlighted the impact of capnothorax in children by measuring regional cerebral oxygen saturation (rcSO2) with near infrared spectroscopy. In this systematic review, we aimed to summarize the data from relevant studies and assess whether thoracoscopy in children is associated with intraoperative pathological cerebral desaturation. Methods: The authors systematically searched four databases for relevant studies on the measurement of rcSO2 during pediatric thoracoscopic procedures. The primary outcome was the proportion of patients with pathological desaturation, that is, >20% decline in the intraoperative rcSO2. Risk of bias among the included studies was estimated using the Newcastle-Ottawa scale. Results: The systematic search resulted in 776 articles, of which 7 studies were included in the analysis. In total, 88 patients (99 procedures) with an age ranging from 0 days to 8.1 years were included. Of these, 43 (49%) patients were neonates. The included cohort had esophageal atresia and tracheoesophageal fistula (n = 26), long-gap esophageal atresia (n = 5), congenital diaphragmatic hernia (n = 14), and congenital pulmonary airway malformations and other conditions needing lung resection (n = 43). Of the total 99 procedures, pathological desaturation was noticed in 13 (13.1%, 95% confidence interval 7.2-21.4) of them. Upon quality assessment, most of the studies were weaker in the selection and comparability domains. Conclusion: In this review, pathological cerebral desaturation was noticed in 13.1% of the pediatric thoracoscopic procedures. However, due to limited methodological quality of the included studies, further randomized multicentric studies comparing rcSO2 in open versus thoracoscopic surgeries are needed to derive definitive conclusions.

Peripheral muscle fractional tissue oxygen extraction in stable term and preterm neonates during the first 24 h after birth

Background

Peripheral muscle fractional tissue oxygen extraction (pFTOE) represents the relative extraction of oxygen from the arterial to venous compartment, providing information about dynamic changes of oxygen delivery and oxygen consumption. The aim of the present study was to establish reference values of pFTOE during the first 24 h after birth in stable term and late preterm neonates.

Methods

The present study is a post-hoc analysis of secondary outcome parameters of prospective observational studies. Only stable neonates without infection, asphyxia and any medical support were eligible for our analysis to obtain normal values. For measurements of peripheral muscle tissue oxygenation index (pTOI) during the first 24 h after birth in term and preterm neonates, the NIRO200/NIRO200NX was used. Arterial oxygen saturation (SpO2) was obtained by pulse oximetry. pFTOE was calculated out of pTOI and SpO2: pFTOE = (SpO2-pTOI)/SpO2. Measurements of neonates were stratified into four groups according to their respective measurement time point (6 h periods) after birth. Term and preterm neonates were analyzed separately. Mean values of measurements during the first time period (0-6 h after birth) were compared to measurements of the following time periods (second = 7-12 h, third = 13-18 h, fourth = 19-24 h after birth).

Results

Two-hundred-fourty neonates (55 term and 185 late preterm neonates) had at least one peripheral muscle NIRS measurements within the first 24 h after birth. Mean gestational age and birth weight were 39.4 ± 1.1 weeks and 3360 (2860-3680)g in term neonates and 34.0 ± 1.4 weeks and 2060 (1750-2350)g in preterm neonates, respectively. In term neonates pFTOE was 0.264 (0.229-0.300), 0.228 (0.192-0.264), 0.237 (0.200-0.274) and 0.220 (0.186-0.254) in the first, second, third and fourth time period. In preterm neonates pFTOE was 0.229 (0.213-0.246), 0.225 (0.209-0.240), 0.226 (0.210-0.242) and 0.238 (0.222-0.255) in the first, second, third and fourth time period. pFTOE did not show any significant changes between the time periods, neither in term nor in preterm neonates.

Conclusion

We provide reference values of pFTOE for stable term and late preterm neonates within the first 24 h after birth, which were stable when comparing four 6-h periods. These normal values are of great need for interpreting pFTOE in scientific context as well as for potential future clinical applications.

Newer indications for neuromonitoring in critically ill neonates

Continuous neuromonitoring in the neonatal intensive care unit allows for bedside assessment of brain oxygenation and perfusion as well as cerebral function and seizure identification. Near-infrared spectroscopy (NIRS) reflects the balance between oxygen delivery and consumption, and use of multisite monitoring of regional oxygenation provides organ-specific assessment of perfusion. With understanding of the underlying principles of NIRS as well as the physiologic factors which impact oxygenation and perfusion of the brain, kidneys and bowel, changes in neonatal physiology can be more easily recognized by bedside providers, allowing for appropriate, targeted interventions. Amplitude-integrated electroencephalography (aEEG) allows continuous bedside evaluation of cerebral background activity patterns indicative of the level of cerebral function as well as identification of seizure activity. Normal background patterns are reassuring while abnormal background patterns indicate abnormal brain function. Combining brain monitoring information together with continuous vital sign monitoring (blood pressure, pulse oximetry, heart rate and temperature) at the bedside may be described as multi-modality monitoring and facilitates understanding of physiology. We describe 10 cases in critically ill neonates that demonstrate how comprehensive multimodal monitoring provided greater recognition of the hemodynamic status and its impact on cerebral oxygenation and cerebral function thereby informing treatment decisions. We anticipate that there are numerous other uses of NIRS as well as NIRS in conjunction with aEEG which are yet to be reported.

Neuromonitoring in neonatal critical care part II: extremely premature infants and critically ill neonates

Neonatal intensive care has expanded from cardiorespiratory care to a holistic approach emphasizing brain health. To best understand and monitor brain function and physiology in the neonatal intensive care unit (NICU), the most commonly used tools are amplitude-integrated EEG, full multichannel continuous EEG, and near-infrared spectroscopy. Each of these modalities has unique characteristics and functions. While some of these tools have been the subject of expert consensus statements or guidelines, there is no overarching agreement on the optimal approach to neuromonitoring in the NICU. This work reviews current evidence to assist decision making for the best utilization of these neuromonitoring tools to promote neuroprotective care in extremely premature infants and in critically ill neonates. Neuromonitoring approaches in neonatal encephalopathy and neonates with possible seizures are discussed separately in the companion paper. IMPACT: For extremely premature infants, NIRS monitoring has a potential role in individualized brain-oriented care, and selective use of aEEG and cEEG can assist in seizure detection and prognostication. For critically ill neonates, NIRS can monitor cerebral perfusion, oxygen delivery, and extraction associated with disease processes as well as respiratory and hypodynamic management. Selective use of aEEG and cEEG is important in those with a high risk of seizures and brain injury. Continuous multimodal monitoring as well as monitoring of sleep, sleep-wake cycling, and autonomic nervous system have a promising role in neonatal neurocritical care.

Carbon dioxide levels in neonates: what are safe parameters?

There is no consensus on the optimal pCO₂ levels in the newborn. We reviewed the effects of hypercapnia and hypocapnia and existing carbon dioxide thresholds in neonates. A systematic review was conducted in accordance with the PRISMA statement and MOOSE guidelines. Two hundred and ninety-nine studies were screened and 37 studies included. Covidence online software was employed to streamline relevant articles. Hypocapnia was associated with predominantly neurological side effects while hypercapnia was linked with neurological, respiratory and gastrointestinal outcomes and Retinpathy of prematurity (ROP). Permissive hypercapnia did not decrease periventricular leukomalacia (PVL), ROP, hydrocephalus or air leaks. As safe pCO₂ ranges were not explicitly concluded in the studies chosen, it was indirectly extrapolated with reference to pCO₂ levels that were found to increase the risk of neonatal disease. Although PaCO₂ ranges were reported from 2.6 to 8.7 kPa (19.5-64.3 mmHg) in both term and preterm infants, there are little data on the safety of these ranges. For permissive hypercapnia, parameters described for bronchopulmonary dysplasia (BPD; PaCO₂ 6.0-7.3 kPa: 45.0-54.8 mmHg) and congenital diaphragmatic hernia (CDH; PaCO₂ ≤ 8.7 kPa: ≤65.3 mmHg) were identified. Contradictory findings on the effectiveness of permissive hypercapnia highlight the need for further data on appropriate CO₂ parameters and correlation with outcomes. IMPACT: There is no consensus on the optimal pCO₂ levels in the newborn. There is no consensus on the effectiveness of permissive hypercapnia in neonates. A safe range of pCO₂ of 5-7 kPa was inferred following systematic review.

Cerebral oxygen saturation and autoregulation during hypotension in extremely preterm infants

BACKGROUND

The impact of the permissive hypotension approach in clinically well infants on regional cerebral oxygen saturation (rScO₂) and autoregulatory capacity (CAR) remains unknown.

METHODS

Prospective cohort study of blinded rScO₂ measurements within a randomized controlled trial of management of hypotension (HIP trial) in extremely preterm infants. rScO₂, mean arterial blood pressure, duration of cerebral hypoxia, and transfer function (TF) gain inversely proportional to CAR, were compared between hypotensive infants randomized to receive dopamine or placebo and between hypotensive and non-hypotensive infants, and related to early intraventricular hemorrhage or death.

RESULTS

In 89 potentially eligible HIP trial patients with rScO₂ measurements, the duration of cerebral hypoxia was significantly higher in 36 hypotensive compared to 53 non-hypotensive infants. In 29/36 hypotensive infants (mean GA 25 weeks, 69% males) receiving the study drug, no significant difference in rScO₂ was observed after dopamine (n = 13) compared to placebo (n = 16). Duration of cerebral hypoxia was associated with early intraventricular hemorrhage or death.  Calculated TF gain (n = 49/89) was significantly higher reflecting decreased CAR in 16 hypotensive compared to 33 non-hypotensive infants.

CONCLUSIONS

Dopamine had no effect on rScO₂ compared to placebo in hypotensive infants. Hypotension and cerebral hypoxia are associated with early intraventricular hemorrhage or death.

IMPACT

Treatment of hypotension with dopamine in extremely preterm infants increases mean arterial blood pressure, but does not improve cerebral oxygenation. Hypotensive extremely preterm infants have increased duration of cerebral hypoxia and reduced cerebral autoregulatory capacity compared to non-hypotensive infants. Duration of cerebral hypoxia and hypotension are associated with early intraventricular hemorrhage or death in extremely preterm infants. Since systematic treatment of hypotension may not be associated with better outcomes, the diagnosis of cerebral hypoxia in hypotensive extremely preterm infants might guide treatment.

Current state of noninvasive, continuous monitoring modalities in pediatric anesthesiology

PURPOSE OF REVIEW

The last decades, anesthesia has become safer, partly due to developments in monitoring. Advanced monitoring of children under anesthesia is challenging, due to lack of evidence, validity and size constraints. Most measured parameters are proxies for end organ function, in which an anesthesiologist is actually interested. Ideally, monitoring should be continuous, noninvasive and accurate. This present review summarizes the current literature on noninvasive monitoring in noncardiac pediatric anesthesia.

RECENT FINDINGS

For cardiac output (CO) monitoring, bolus thermodilution is still considered the gold standard. New noninvasive techniques based on bioimpedance and pulse contour analysis are promising, but require more refining in accuracy of CO values in children. Near-infrared spectroscopy is most commonly used in cardiac surgery despite there being no consensus on safety margins. Its place in noncardiac anesthesia has yet to be determined. Transcutaneous measurements of blood gases are used mainly in the neonatal intensive care unit, and is finding its way to the pediatric operation theatre. Especially CO2 measurements are accurate and useful.

SUMMARY

New techniques are available to assess a child's hemodynamic and respiratory status while under anesthesia. These new monitors can be used as complementary tools together with standard monitoring in children, to further improve perioperative safety.

Is Anesthesia Bad for the Brain? Current Knowledge on the Impact of Anesthetics on the Developing Brain

There are compelling preclinical data that common general anesthetics cause increased neuroapoptosis in juvenile animals. Retrospective studies demonstrate that young children exposed to anesthesia have school difficulties, which could be caused by anesthetic neurotoxicity, perioperative hemodynamic and homeostatic instability, underlying morbidity, or the neuroinflammatory effects of surgical trauma. Unnecessary procedures should be avoided. Baseline measures of blood pressure are important in determining perioperative blood pressure goals. Inadvertent hypocapnia or moderate hypercapnia and hyperoxia or hypoxia should be avoided. Pediatric patients should be maintained in a normothermic, euglycemic state with neutral positioning. Improving outcomes of infants and children requires the collaboration of anesthesiologists, surgeons, pediatricians and neonatologists.

Beyond Anesthesia Toxicity: Anesthetic Considerations to Lessen the Risk of Neonatal Neurological Injury

Infants who undergo surgical procedures in the first few months of life are at a higher risk of death or subsequent neurodevelopmental abnormalities. Although the pathogenesis of these outcomes is multifactorial, an understanding of the nature and pathogenesis of brain injury in these infants may assist the anesthesiologist in consideration of their day-to-day practice to minimize such risks. This review will summarize the main types of brain injury in preterm and term infants and their key pathways. In addition, the review will address key potential pathogenic pathways that may be modifiable including intraoperative hypotension, hypocapnia, hyperoxia or hypoxia, hypoglycemia, and hyperthermia. Each of these conditions may increase the risk of perioperative neurological injury, but their long-term ramifications are unclear.

A practical approach to cerebral near-infrared spectroscopy (NIRS) directed hemodynamic management in noncardiac pediatric anesthesia

Safeguarding cerebral function is of major importance during pediatric anesthesia. Premature, ex-premature, and full-term neonates can be vulnerable to physiological changes that occur during anesthesia and surgery. Data from studies performed during pediatric cardiac surgery and in neonatal/pediatric intensive care units have shown the benefits of near-infrared spectroscopy (NIRS) monitoring of regional cerebral oxygenation (c-rSO₂ ). However, NIRS monitoring is seldom used during noncardiac pediatric anesthesia. Despite compelling evidence that blood pressure does not reflect end-organ perfusion, it is still regarded as the most important determinant of cerebral perfusion and the most relevant hemodynamic management target parameter by most (pediatric) anesthetists. The principle of NIRS monitoring is not self-explanatory and sometimes seems even counterintuitive, which may explain why many anesthesiologists are reserved regarding its use. The first part of this paper is dedicated to a clinical introduction to NIRS monitoring. Despite scientific efforts, it has not yet been possible to define individual lower limit c-rSO₂ values and it is unlikely this will succeed in the near future. Nonetheless, published treatment algorithms usually specify c-rSO₂ values which may be associated with cerebral hypoxia. Our treatment guideline for maintaining sufficient cerebral oxygenation differs fundamentally from all previously published approaches. We define a baseline c-rSO₂ value, registered in the awake child prior to anesthesia induction, as the lowest acceptable limit during anesthesia and surgery. The cerebral rSO₂ is the single target parameter, while blood pressure, heart rate, P_a CO₂ , and SaO₂ are major parameters that determine the c-rSO2. Cerebral NIRS monitoring, interpreted together with its continuously available contributing parameters, may help avoid potentially harmful episodes of cerebral desaturation in anesthetized pediatric patients.

Interpretation of Cerebral Oxygenation Changes in the Preterm Infant

Near-infrared spectroscopy (NIRS) allows for continuous, non-invasive monitoring of end-organ tissue oxygenation. The use of NIRS, cerebral NIRS (cNIRS) in particular, in neonatal care has increased significantly over the last few years. This dynamic monitoring technique provides real-time information on the cerebral and haemodynamic status of the neonate and has the potential to serve as an important adjunct to patient care with some centres routinely utilising cNIRS to aid decision-making at the bedside. cNIRS values may be influenced by many variables, including cardiac, respiratory and metabolic parameters, and therefore it is essential to understand the pathophysiology behind alterations in cNIRS values. Correct interpretation is required to direct appropriate patient-specific interventions. This article aims to assist clinicians in deciphering cNIRS values by providing an overview of potential causes of fluctuations in cNIRS values, illustrated by common clinical scenarios, with particular emphasis on the preterm infant.

Does metabolic alkalosis influence cerebral oxygenation in infantile hypertrophic pyloric stenosis?

BACKGROUND

This pilot study focuses on regional tissue oxygenation (rSO₂) in patients with infantile hypertrophic pyloric stenosis in a perioperative setting. To investigate the influence of enhanced metabolic alkalosis (MA) on cerebral (c-rSO₂) and renal (r-rSO₂) tissue oxygenation, two-site near-infrared spectroscopy (NIRS) technology was applied.

MATERIALS AND METHODS

Perioperative c-rSO₂, r-rSO₂, capillary blood gases, and electrolytes from 12 infants were retrospectively compared before and after correction of MA at admission (T1), before surgery (T2), and after surgery (T3).

RESULTS

Correction of MA was associated with an alteration of cerebral oxygenation without affecting renal oxygenation. When compared to T1, 5-min mean (± standard deviation) c-rSO₂ increased after correction of MA at T2 (72.74 ± 4.60% versus 77.89 ± 5.84%; P = 0.058), reaching significance at T3 (80.79 ± 5.29%; P = 0.003). Furthermore, relative 30-min c-rSO₂ values at first 3 h of metabolic compensation were significantly lowered compared with postsurgical states at 16 and 24 h. Cerebral oxygenation was positively correlated with levels of sodium (r = 0.37; P = 0.03) and inversely correlated with levels of bicarbonate (r = -0.34; P = 0.05) and base excess (r = -0.36; P = 0.04). Analysis of preoperative and postoperative cerebral and renal hypoxic burden yielded no differences. However, a negative correlation (r = -0.40; P = 0.03) regarding hematocrite and mean r-rSO₂, indirectly indicative of an increased renal blood flow under hemodilution, was obtained.

CONCLUSIONS

NIRS seems suitable for the detection of a transiently impaired cerebral oxygenation under state of pronounced MA in infants with infantile hypertrophic pyloric stenosis. Correction of MA led to normalization of c-rSO₂. NIRS technology constitutes a promising tool for optimizing perioperative management, especially in the context of a possible diminished neurodevelopmental outcome after pyloromyotomy.

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.

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.

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.

Early red cell transfusion favourably alters cerebral oxygen extraction in very preterm newborns

BACKGROUND

Elevated cerebral fractional tissue oxygen extraction (cFTOE; ≥0.4) predicts early brain injury in very preterm infants. While blood transfusion increases oxygen-carrying capacity, its ability to improve cerebral oxygen kinetics in the immediate newborn period remains unknown.

OBJECTIVE

To investigate the effect of red blood cell (RBC) transfusion in the first 24 h of life on cFTOE in infants ≤29 weeks gestation.

METHODS

cFTOE was calculated from cerebral tissue oxygenation index (TOI) and cutaneous oximetry measured over a 30 min epoch before and after transfusion. Infants were dichotomised according to pre-transfusion cFTOE (low <0.4 vs high ≥0.4).

RESULTS

24 babies were included, 12 in each group. Pre- and post-transfusion Hb were similar between the groups. cFTOE significantly reduced after transfusion in the high but not low-extraction group (p<0.01).

CONCLUSIONS

Early RBC transfusion favourably alters cerebral oxygen kinetics in infants with elevated cFTOE, showing potential for modification of the risk of hypoxic (brain) injury.

Cesarean under general or epidural anesthesia: does it differ in terms of regional cerebral oxygenation?

OBJECTIVE

It is aimed to evaluate whether there is a difference in regional cerebral saturation of newborns measured by near infrared spectroscopy born either by general anesthesia or combined spinal epidural anesthesia during elective cesarean deliveries.

METHODS

After approval from the ethics committee of our hospital, and informed consents of the parturients were taken, 68 patients were included in the study. The regional cerebral oxygen saturations (RcSO2) of newborns were measured by near infrared spectroscopy (NIRS) measurements at 1st, 5th min after birth. In group I (n=32), general anesthesia was performed for the cesarean operation and in group II (n=36), combined spinal epidural anesthesia (CSEA) was the anesthetic management. The age of the mother, gestation, the problems related to the pregnancy, heart rate, blood pressure, oxygen saturation (SpO2) of the mother had been recorded. The measurements of the newborn were; SpO2 of right hand, RcSO2 measured by NIRS, the delivery time (from incision to the cessation of circulation in the placental cord), Apgar score. Data were analyzed using GraphPad Prism 5.0 (GraphPad Software, La Jolla, California) and presented as mean +/- SD. Results obtained in different groups were compared using upaired t-test. Differences were statistically significant at p < 0.05.

RESULTS

There were no significant differences between the groups related to the mother's age, gestation week and baseline blood pressure. Both the systolic and diastolic blood pressures measured at 1st and 5th min after induction or start of the spinal block were significantly lower in the mothers who had undergone combined spinal epidural anesthesia. The heart rates of the mothers who had been under CSEA were significantly higher than the general anesthesia group. The Apgar at the 1st min were observed significantly higher in Group II. Oxygen saturation of the newborns were significantly higher in Group II. Regional cerebral oxygenation measured by NIRS were significantly higher in CSEA group.

CONCLUSION

Combined spinal epidural anesthesia, besides other known advantages, had been shown to be superior to general anesthesia as a means of regional cerebral oxygenation of the newborns.

Intracranial pressure and cerebrovascular autoregulation in pediatric critical illness

Protecting the brain in vulnerable infants and children with critical illness involving the brain is a central aspect of pediatric intensive care and neurocritical care. Collectively, illness-induced derangements in intracranial pressure, circulatory homeostasis, and pressure autoregulation are all fundamental in informing bedside management. Therefore, this review provides an understanding of these entities and a physiological approach to bedside care and monitoring.

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.

Perioperative central nervous system injury in neonates

Anaesthetic-induced developmental neurotoxicity (AIDN) has been clearly established in laboratory animal models. The possibility of neurotoxicity during uneventful anaesthetic procedures in human neonates or infants has led to serious questions about the safety of paediatric anaesthesia. However, the applicability of animal data to clinical anaesthesia practice remains uncertain. The spectre of cerebral injury due to cerebral hypoperfusion, metabolic derangements, coexisting disease, and surgery itself further muddles the picture. Given the potential magnitude of the public health importance of this issue, the clinician should be cognisant of the literature and ongoing investigations on AIDN, and raise awareness of the risks of both surgery and anaesthesia.

A left-to-right shunt via the ductus arteriosus is associated with increased regional cerebral oxygen saturation during neonatal transition

BACKGROUND

Oxygen delivery to the brain is dependent on cardiac output and arterial oxygen content.

OBJECTIVES

The study was designed to investigate the influence of a left-to-right shunt via the ductus arteriosus (DA) on regional oxygen saturation (rSO2) of the brain and peripheral tissue during postnatal transition.

METHODS

Nested case-control study. In term neonates after elective cesarian section, rSO2 of the brain and pre- and postductal peripheral tissue were measured 15 min after uncomplicated postnatal transition. Two groups were formed according to shunt flow characteristics via the DA: shunt group (with a left-to-right shunt), and nonshunt group (no shunt).

RESULTS

Of 80 infants, in 58 (72%) a left-to-right shunt was identified, and in 22 (28%) no flow was seen via the DA. The 22 infants formed the nonshunt group. They were matched with 22 newborn infants with a left-to-right shunt via the DA (shunt group). Infants in the nonshunt group had significantly lower cerebral rSO2 values and higher fractional tissue oxygen extraction and heart rate values. There were no significant differences in regard to peripheral rSO2 values.

CONCLUSION

During postnatal transition, term infants with a left-to-right shunt via the DA have significantly higher cerebral rSO2 values compared to infants without shunt flow.

The SafeBoosC phase II randomised clinical trial: a treatment guideline for targeted near-infrared-derived cerebral tissue oxygenation versus standard treatment in extremely preterm infants

Near-infrared spectroscopy-derived regional tissue oxygen saturation of haemoglobin (rStO2) reflects venous oxygen saturation. If cerebral metabolism is stable, rStO2 can be used as an estimate of cerebral oxygen delivery. The SafeBoosC phase II randomised clinical trial hypothesises that the burden of hypo- and hyperoxia can be reduced by the combined use of close monitoring of the cerebral rStO2 and a treatment guideline to correct deviations in rStO2 outside a predefined target range.

AIMS

To describe the rationale for and content of this treatment guideline.

METHODS

Review of the literature and assessment of the quality of evidence and the grade of recommendation for each of the interventions.

RESULTS AND CONCLUSIONS

A clinical intervention algorithm based on the main determinants of cerebral perfusion-oxygenation changes during the first hours after birth was generated. The treatment guideline is presented to assist neonatologists in making decisions in relation to cerebral oximetry readings in preterm infants within the SafeBoosC phase II randomised clinical trial. The evidence grades were relatively low and the guideline cannot be recommended outside a research setting.

Effect of balloon atrial septostomy on cerebral oxygenation in neonates with transposition of the great arteries

BACKGROUND

The aim of this study was to determine the effect of balloon atrial septostomy (BAS) on cerebral oxygenation in neonates with transposition of the great arteries (TGA).

METHODS

In term neonates with TGA, regional cerebral tissue oxygen saturation (r(c)SO(2)) was measured using near-infrared spectroscopy (NIRS) for a period of 2 h, before BAS, after BAS, and 24 h after BAS. In neonates who did not require BAS on clinical grounds, r(c)SO(2) was measured within 24 h of admission and 24 h later.

RESULTS

BAS was performed in 12 of 21 neonates. r(c)SO(2) increased from a median of 42% (before) to 48% at 2 h after BAS (P < 0.05), as did transcutaneous arterial oxygen saturation (spO(2)) (from 72% to 85%, P < 0.01). r(c)SO(2) increased further during the next 24 h (from 48% to 64%, P < 0.05), whereas spO(2) remained stable. Although beginning from a lower baseline (42 vs. 51%, P < 0.01), r(c)SO(2) was higher in neonates treated with BAS, as compared with neonates not treated with BAS, 24 h after the procedure (64 vs. 58%, P < 0.05); spO(2) was, however, similar between the two groups.

CONCLUSION

BAS improves cerebral oxygen saturation in neonates with TGA. Complete recovery of cerebral oxygen saturation occurred only 24 h after BAS.

Understanding near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) is a noninvasive technique that monitors regional tissue oxygenation reflecting perfusion status. Near-infrared spectroscopy has the ability to continuously and simultaneously monitor tissue perfusion in different organ systems at the bedside without interrupting routine care. Research has demonstrated its benefit in monitoring cerebral, intestinal, and renal perfusion to detect potential ischemic episodes. Near-infrared spectroscopy can augment current physiologic monitoring to increase awareness of abnormal perfusion status in the preterm population and potentially reduce risks associated with many diseases that may lead to ischemic injury. This article provides an overview describing NIRS technology and function, its current use in neonatology, and pertinent research findings illustrating its benefit in the neonatal population. Near-infrared spectroscopy may evolve into an important diagnostic and prognostic tool for neonatal treatment and outcome.

The relationship between electrocerebral activity and cerebral fractional tissue oxygen extraction in preterm infants

Impaired cerebral oxygen delivery may cause cerebral damage in preterm infants. At lower levels of cerebral perfusion and oxygen concentration, electrocerebral activity is disturbed. The balance between cerebral oxygen delivery and oxygen use can be measured by near-infrared spectroscopy (NIRS), and electrocerebral activity can be measured by amplitude-integrated EEG (aEEG). Our aim was to determine the relationship between regional cerebral tissue oxygen saturation (rcSO2), fractional tissue oxygen extraction (FTOE), and aEEG. We recorded longitudinal digital aEEG and rcSO2 prospectively in 46 preterm infants (mean GA 29.5 wk, SD 1.7) for 2 hr on the 1st to 5th, 8th, and 15th d after birth. We excluded infants with germinal matrix hemorrhage exceeding grade I and recordings of infants receiving inotropes. FTOE was calculated using transcutaneous arterial oxygen saturation (tcSaO2) and rcSO2 values: (tcSaO2 - rcSO2)/tcSaO2. aEEG was assessed by calculating the mean values of the 5th, 50th, and 95th centiles of the aEEG amplitudes. The aEEG amplitude centiles changed with increasing GA. FTOE and aEEG amplitude centiles increased significantly with postnatal age. More mature electrocerebral activity was accompanied by increased FTOE. FTOE also increased with increasing postnatal age and decreasing Hb levels.

Regional oxygen saturation of the brain during birth transition of term infants: comparison between elective cesarean and vaginal deliveries

OBJECTIVE

To evaluate differences in regional oxygen saturation of the brains of term infants of vaginal or cesarean deliveries.

STUDY DESIGN

Vaginal delivery (n = 63) and elective cesarean delivery infants were prospectively evaluated for the first 10 minutes after delivery. Peripheral arterial oxygen saturation (SpO(2)) and heart rate were measured on the right hand using pulsoximetry with near infrared spectroscopy. Regional oxygen saturation of the brain (rSO(2)brain) was measured. Fractional tissue oxygen extraction was calculated for each minute.

RESULTS

From 4 to 8 minutes, SpO(2) values for cesarean delivery infants were significantly lower than for vaginally delivered infants. Heart rate of the cesarean delivery infants was significantly lower throughout the whole observation period. There was no difference between groups in rSO(2)brain. Fractional tissue oxygen extraction only differed at minute 10.

CONCLUSIONS

Although SpO(2) and heart rate were significantly lower in cesarean-delivered infants, there were no differences in rSO(2)brain with respect to mode of delivery.

Inconsistent detection of changes in cerebral blood volume by near infrared spectroscopy in standard clinical tests

The attractive possibility of near infrared spectroscopy (NIRS) to noninvasively assess cerebral blood volume and oxygenation is challenged by the possible interference from extracranial tissues. However, to what extent this may affect cerebral NIRS monitoring during standard clinical tests is ignored. To address this issue, 29 healthy subjects underwent a randomized sequence of three maneuvers that differently affect intra- and extracranial circulation: Valsalva maneuver (VM), hyperventilation (HV), and head-up tilt (HUT). Putative intracranial ("i") and extracranial ("e") NIRS signals were collected from the forehead and from the cheek, respectively, and acquired together with cutaneous plethysmography at the forehead (PPG), cerebral blood velocity from the middle cerebral artery, and arterial blood pressure. Extracranial contribution to cerebral NIRS monitoring was investigated by comparing Beer-Lambert (BL) and spatially resolved spectroscopy (SRS) blood volume indicators [the total hemoglobin concentration (tHb) and the total hemoglobin index, (THI)] and by correlating their changes with changes in extracranial circulation. While THIe and tHbe generally provided concordant indications, tHbi and THIi exhibited opposite-sign changes in a high percentage of cases (VM: 46%; HV: 31%; HUT: 40%). Moreover, tHbi was correlated with THIi only during HV (P < 0.05), not during VM and HUT, while it correlated with PPG in all three maneuvers (P < 0.01). These results evidence that extracranial circulation may markedly affect BL parameters in a high percentage of cases, even during standard clinical tests. Surface plethysmography at the forehead is suggested as complementary monitoring helpful in the interpretation of cerebral NIRS parameters.

Advances in near-infrared spectroscopy to study the brain of the preterm and term neonate

This article reviews tissue oximetry and imaging to study the preterm and newborn infant brain by near-infrared spectroscopy. These two technologies are now advanced; nearly 100 reports on their use in newborn infants have been published, and commercial instruments are available. The precision of oximetry, however, is a limitation for its clinical use of assessing cerebral oxygenation. Imaging of brain function needs very well defined protocols for sensory stimulation as well as signal analysis to provide meaningful results.

The brains of very preterm newborns in clinically stable condition may be hyperoxygenated

OBJECTIVE

The objective was to compare cerebral oxygenation in preterm newborns with that in healthy term newborns.

METHODS

Forty-six preterm newborns with gestational ages of <33 weeks and 25 healthy term newborns were included. The cerebral tissue oxygenation index (c-TOI) was measured by using near-infrared spectroscopy in clinical steady state on the first day of life (median age: 19.2 hours). The mean gestational ages and birth weights in the 2 groups were 29.1 +/- 2.6 weeks versus 39.7 +/- 1.3 weeks and 1307 +/- 437 g versus 3484 +/- 346 g, respectively. Three preterm infants needed mechanical ventilation and 11 received inotropic drugs. Later, 3 preterm infants developed intraventricular hemorrhage and 2 infants died. All term infants were healthy newborns recruited in the maternity ward.

RESULTS

There was a significant difference in c-TOI (preterm: 78.6% [95% confidence interval: 76.9%-80.3%]; term: 74.7% [95% confidence interval: 72.3%-77.1%]). Preterm newborns had significantly lower fractional tissue oxygen extraction, which suggests lower oxygen extraction in this group. There was no significant correlation between head size and c-TOI. The mean peripheral oxygen saturation was 95% in both groups. The median blood Pco(2) for the preterm infants was 6.1 kPa (range: 3.4-7.3 kPa).

CONCLUSIONS

Cerebral oxygenation on the first day of life was higher in a group of relatively healthy, very preterm infants in stable condition, compared with healthy term newborns. Slightly elevated blood Pco(2) could be the explanation. Prematurity itself does not seem to dispose preterm infants to global cerebral hypoxia.

Cerebral oxygen saturation and extraction in preterm infants with transient periventricular echodensities

OBJECTIVE

Our aim was to determine regional cerebral tissue oxygen saturation and fractional tissue oxygen extraction in preterm infants with transient periventricular echodensities. We hypothesized that as a result of reduced cerebral perfusion, regional cerebral tissue oxygen saturation will be lower and fractional tissue oxygen extraction will be higher during the first days after birth.

PATIENTS AND METHODS

This was a prospective, observational study of 49 preterm infants (gestational age median: 30.1 weeks [26.0-31.8 weeks]; birth weight median: 1220 g [615-2250 g]). We defined transient periventricular echodensities as echodensities that persisted for >7 days. Regional cerebral tissue oxygen saturation was measured on days 1-5, 8, and 15 after birth. Fractional tissue oxygen extraction was calculated as (transcutaneous arterial oxygen saturation--regional cerebral tissue oxygen saturation)/transcutaneous arterial oxygen saturation.

RESULTS

Transient periventricular echodensities were found in 25 of 49 infants. During the first week we found no difference between the 2 groups for cerebral tissue oxygen saturation and fractional tissue oxygen extraction values. On day 15 after birth, cerebral tissue oxygen saturation was lower in preterm infants with transient periventricular echodensities (66%) compared with infants without echodensities (76%) (P = .003). Fractional tissue oxygen extraction in infants with transient periventricular echodensities (0.30) was higher than fractional tissue oxygen extraction in infants without transient periventricular echodensities (0.20) (P < .001). The differences could not be explained by confounding variables.

CONCLUSIONS

Persistent transient periventricular echodensities may be associated with increased cerebral oxygen demand after the first week after birth, which is contrary to our hypothesis. Cerebral oxygenation may be involved in the recovery of perinatal white matter damage.