pFOE or pFTOE as an Early Marker for Impaired Peripheral Microcirculation in Neonates.

BACKGROUND: Peripheral-muscle-fractional-oxygen-extraction (pFOE) and peripheral-muscle-fractional-tissue-oxygen-extraction (pFTOE) are often equated, since both parameters are measured with near-infrared-spectroscopy (NIRS) and estimate oxygen extraction in the tissue. The aim was to investigate the comparability of both parameters and their potential regarding detection of impaired microcirculation. METHODS: Term and preterm neonates with NIRS measurements of upper (UE) and lower extremities (LE) were included. pFOE was calculated out of peripheral-muscle-mixed-venous-saturation (pSvO2), measured with NIRS and venous occlusion, and arterial oxygen saturation (SpO2). pFTOE was calculated out of peripheral-muscle-tissue-oxygen-saturation and SpO2. Both parameters were compared using Wilcoxon-Signed-Rank-test and Bland-Altman plots. RESULTS: 341 NIRS measurements were included. pFOE was significantly higher than pFTOE in both locations. Bland-Altman plots revealed limited comparability, especially with increasing oxygen extraction with higher values of pFOE compared to pFTOE. CONCLUSION: The higher pFOE compared to pFTOE suggests a higher potential of pFOE to detect impaired microcirculation, especially when oxygen extraction is elevated.

Three Physiological Components That Influence Regional Cerebral Tissue Oxygen Saturation.

Near-infrared spectroscopy (NIRS) measurement of regional cerebral tissue oxygen saturation (rcStO2) has become a topic of high interest in neonatology. Multiple studies have demonstrated that rcStO2 measurements are feasible in the delivery room during immediate transition and resuscitation as well as after admission to the neonatal intensive care unit. Reference ranges for different gestational ages, modes of delivery, and devices have already been published. RcStO2 reflects a mixed tissue saturation, composed of arterial (A), venous (V), and capillary signals, derived from small vessels within the measurement compartment. The A:V signal ratio fluctuates based on changes in oxygen delivery and oxygen consumption, which enables a reliable trend monitoring of the balance between these two parameters. While the increasing research evidence supports its use, the interpretation of the absolute values of and trends in rcStO2 is still challenging, which halts its routine use in the delivery room and at the bedside. To visualize the influencing factors and improve the understanding of rcStO2 values, we have created a flowchart, which focuses on the three major physiological components that affect rcStO2: oxygen content, circulation, and oxygen extraction. Each of these has its defining parameters, which are discussed in detail in each section.

Fetal to neonatal transition: what additional information can be provided by cerebral near infrared spectroscopy?

This narrative review focuses on the clinical use and relevance of cerebral oxygenation measured by NIRS during fetal to neonatal transition. Cerebral NIRS(cNIRS) offers the possibility of non-invasive, continuous, and objective brain monitoring in addition to the recommended routine monitoring. During the last decade, with growing interest in early and sensitive brain monitoring, many research groups worldwide have been working with cNIRS and verified the feasibility of cNIRS monitoring immediately after birth. Cerebral hypoxia during fetal to neonatal transition, defined as cerebral oxygenation values below10th percentile, seems to have an impact on neurological outcomes. Feasibility to guide clinical support using cNIRS to reduce the burden of cerebral hypoxia has been shown. It is well known that in some cases cerebral oxygenation follows different patterns than SpO2. Cerebral oxygenation does not only depend on systemic oxygenation, hemoglobin content and cerebral blood flow, but also on cardiocirculatory condition, ventilation, and metabolic parameters. Hence, measurement of cerebral oxygenation may uncover problems not detectable by standard monitoring. Therefore, applying NIRS can provide caregivers a more complete clinical overview, especially in critically ill neonates. In this review, we aim to describe the additional information which can be provided by cNIRS during fetal to neonatal transition. IMPACT: This narrative review focuses on the clinical use and relevance of cerebral oxygenation measured by near infrared spectroscopy (NIRS) during fetal to neonatal transition. During the last decade, interest on brain monitoring is growing continuously as the measurement of cerebral oxygenation may uncover problems which are not detectable by routine monitoring. Therefore, it will be crucial to have additional information to get a complete overview, especially in critically ill neonates in need of medical and respiratory support. In this review, we offer additional information which can be provided by cerebral NIRS during fetal to neonatal transition.

Impact of bradycardia and hypoxemia on oxygenation in preterm infants requiring respiratory support at birth.

AIM OF THE STUDY: Analysis of the impact of bradycardia and hypoxemia on the course of cerebral and peripheral oxygenation parameters in preterm infants in need for respiratory support during foetal-to-neonatal transition. METHODS: The first 15 min after birth of 150 preterm neonates in need for respiratory support born at the Division of Neonatology, Graz (Austria) were analyzed. Infants were divided into different groups according to duration of bradycardia exposure (no Bradycardia, brief bradycardia <2 min, and prolonged bradycardia ≥2 min) and to systemic oxygen saturation (SpO2) value at 5 min of life (<80% or ≥80%). Analysis was performed considering the degree of bradycardia alone (step 1) and in association with the presence of hypoxemia (step 2). RESULTS: In step 1, courses of SpO2 differed significantly between bradycardia groups (p = 0.002), while courses of cerebral regional oxygen saturation (crStO2) and cerebral fractional tissue oxygen extraction (cFTOE) were not influenced (p = 0.382 and p = 0.878). In step 2, the additional presence of hypoxemia had a significant impact on the courses of SpO2 (p < 0.001), crStO2 (p < 0.001) and cFTOE (p = 0.045). CONCLUSION: Our study shows that the degree of bradycardia has a significant impact on the course of SpO2 only, but when associated with the additional presence of hypoxemia a significant impact on cerebral oxygenation parameters was seen (crStO2, cFTOE). Furthermore, the additional presence of hypoxemia has a significant impact on FiO2 delivered. Our study emphasizes the importance of HR and SpO2 during neonatal resuscitation, underlining the relevance of hypoxemia during the early transitional phase.

Association between Regional Tissue Oxygenation and Body Temperature in Term and Preterm Infants Born by Caesarean Section.

Body temperature (BT) management remains a challenge in neonatal intensive care, especially during resuscitation after birth. Our aim is to analyze whether there is an association between the BT and cerebral and peripheral tissue oxygen saturation (crSO2/cTOI and prSO2), arterial oxygen saturation (SpO2), and heart rate (HR). The secondary outcome parameters of five prospective observational studies are analyzed. We include preterm and term neonates born by Caesarean section who received continuous pulse oximetry and near-infrared spectroscopy monitoring during the first 15 min, and a rectal BT measurement once in minute 15 after birth. Four-hundred seventeen term and 169 preterm neonates are included. The BT did not correlate with crSO2/cTOI and SpO2. The BT correlated with the HR in all neonates (ρ = 0.210, p < 0.001) and with prSO2 only in preterm neonates (ρ = -0.285, p = 0.020). The BT was lower in preterm compared to term infants (36.7 [36.4-37.0] vs. 36.8 [36.6-37.0], p = 0.001) and prevalence of hypothermia was higher in preterm neonates (29.5% vs. 12.0%, p < 0.001). To conclude, the BT did not correlate with SpO2 and crSO2/cTOI, however, there was a weak positive correlation between the BT and the HR in the whole cohort and a weak correlation between the BT and prSO2 only in preterm infants. Preterm neonates had a statistically lower BT and suffered significantly more often from hypothermia during postnatal transition.

Effect of Intrauterine Growth Restriction on Cerebral Regional Oxygen Saturation in Preterm and Term Neonates during Immediate Postnatal Transition.

BACKGROUND: Intrauterine growth restriction (IUGR) is associated with adverse perinatal outcome. Affected fetuses commonly display typical blood flow redistribution towards the brain ("brain sparing"). Accordingly, increased cerebral oxygen saturation has been observed in IUGR neonates within the first days of life. AIM: The aim of our study was to assess cerebral oxygenation behavior during immediate neonatal transition in IUGR infants. METHODS: This is a retrospective single-center observational cohort study. Cerebral regional oxygen saturation (crSO2) was measured with near-infrared spectroscopy in neonates during the first 15 min after birth. Neonates with IUGR (IUGR group) were matched for gestational age (±1 week) and gender with neonates that were appropriate for gestational age (AGA). The AGA:IUGR matching ratio was 3:1. Arterial oxygen saturation (SpO2), heart rate (HR), crSO2, and cerebral fractional tissue oxygen extraction (cFTOE) were compared between the groups. RESULTS: Between August 2010 and October 2017, 45 neonates with IUGR were identified and matched to 135 AGA neonates. Mean gestational age was 33.1 ± 3.0 weeks in the IUGR group and 33.5 ± 2.7 weeks in the AGA group. Mean birth weight was 1,559 ± 582 g in the IUGR group and 2,051 ± 679 g in the AGA group. There was a significant group difference in crSO2 beginning at 5 min and continuing for the rest of the observation time with higher crSO2 values in the IUGR group (main effect group: p = 0.011; interaction time × group: p = 0.039). In cFTOE, a significant difference could be observed at 5-9 and 11-13 min with lower rates of oxygen extraction in the IUGR group (main effect group: p = 0.025; interaction time × group: p = 0.463). Concerning SpO2 and HR, there was no significant difference between the IUGR and the AGA neonates. CONCLUSION: Neonates of the IUGR group did show significantly higher crSO2 values and significantly lower cFTOE values already during immediate neonatal transition compared to the AGA group.

Changes in peripheral muscle oxygenation measured with near-infrared spectroscopy in preterm neonates within the first 24 h after birth.

BACKGROUND: Near-infrared spectroscopy (NIRS) combined with venous occlusions enables peripheral-muscle oxygenation and perfusion monitoring. OBJECTIVE: The aim of the present exploratory observational study was to evaluate peripheral-muscle oxygenation and perfusion during the first 24 h after birth in stable preterm neonates. APPROACH: Secondary outcome parameters of prospective observational studies were analysed. Preterm neonates with peripheral-muscle NIRS measurements combined with venous occlusion on the first day after birth were included. Neonates without circulatory support and without signs of infection/inflammation were included. Neonates were stratified in four groups according to their measurement time-point (6 h-periods) and matched 2:1 for gestational age ±1 week. For each group haemoglobin flow (Hbflow), oxygen-delivery (DO2), oxygen-consumption (VO2), fractional-oxygen-extraction (FOE), tissue-oxygenation-index (TOI) and mixed-venous-oxygenation (SvO2) were calculated. Neonates with measurements during the first 6-hour time period were compared to neonates with measurements of the following time periods. MAIN RESULTS: 40 preterm neonates (gestational age (median(IQR)): 33.5(32.5-34.1)weeks) measured during the first 6 h period after birth were compared to 20 preterm neonates measured in each of the following 6 h periods (period two: 33.7(33.1-34.3)weeks; period three: 34.1(33.2-34.6)weeks; period four: 33.8(32.6-34.6)weeks). Hbflow, DO2 and SvO2 were significantly higher in the second and third 6 h time period compared to the first 6 h period. VO2 did not change significantly during the first day after birth. FOE was significantly lower in the second, third and fourth time period compared to the first 6 h period. TOI showed a non-significant trend towards higher values in the third period compared to the first 6 h period. SIGNIFICANCE: In preterm neonates Hbflow, DO2, SvO2 increased, FOE decreased and TOI showed a trend towards increase during the first day after birth, whereas VO2 did not change. Changes of peripheral-muscle oxygenation during the first day after birth in stable preterm neonates are different to already published changes thereafter.

Cerebral and peripheral tissue oxygenation in stable neonates: Absent influence of cardiac function.

AIM: Cardiac function is a major factor for tissue perfusion and therefore may affect the tissue oxygen saturation. Aim was to analyse possible associations between cardiac function parameters and cerebral and peripheral tissue oxygenation in neonates on the first day after birth. METHODS: For the present study, we analysed secondary outcome parameters of a previously performed prospective single centre observational study. The prospective study was conducted at the Medical University of Graz, Austria between September 2011 and June 2013. We included preterm and term neonates who were admitted to the neonatal intensive care unit and in whom simultaneous near-infrared spectroscopy measurements and echocardiography were obtained on the first day after birth. Cardiac function parameters were correlated to cerebral and peripheral tissue oxygen saturation and cerebral and peripheral fractional tissue oxygen extraction at the time of echocardiography. RESULTS: A total of 60 neonates of whom 47 were preterm and 13 were term (median gestational age: 34; IQR 33-35 weeks, mean birth weight: 2276 ± 774 grams) were included. There were no statistically significant correlations between cardiac function parameters and regional tissue oxygenation parameters. CONCLUSION: In the present study, we found no correlation between regional tissue oxygenation and parameters of cardiac function in cardio-circulatory stable neonates on the first day after birth.

Oxygen Saturation Targeting During Delivery Room Stabilization: What Does This Mean for Regional Cerebral Oxygenation?

Objective: To investigate if preterm neonates with arterial oxygen saturation (SpO2)<80% at 5 min after birth show different regional cerebral tissue oxygen saturation (rcStO2), compared to infants reaching the target. Methods: Retrospective analysis of four prospective observational studies. Preterm neonates needing respiratory support during delivery room stabilization were included. Regional cerebral tissue oxygen saturation was measured with near-infrared spectroscopy (NIRS) during the first 15 min after birth along with SpO2 and heart rate (HR). Neonates were divided into two groups: those with a 5-min SpO2 ≥ 80% ("≥80% group") and those with a 5-min SpO2 < 80% ("<80% group"). Groups were compared regarding rcStO2, SpO2, and HR. Furthermore, we analyzed whether a 5-min SpO2 < 80% was associated with a rcStO2 below the 10th percentile at the same time point. Results: 146 neonates were included, with 68 (47%) in the "≥80% group" and 78 (53%) in the "<80% group." Neonates in the " <80% group" had a significantly lower rcStO2 (p < 0.001). Furthermore, 80.3% of neonates in the " <80% group" and 23.4% in the "≥80% group" had rcStO2 values below the 10th percentile at 5 min (p < 0.001). HR was significantly lower at minute 3 and 4 in the " <80% group" (p < 0.002). Conclusion: Preterm infants needing respiratory support, who do not reach the SpO2 target of 80% at 5 min after birth, show significantly diminished rcStO2 values compared to neonates reaching the target.

Novel algorithm to screen for heart murmurs using computer-aided auscultation in neonates: a prospective single center pilot observational study.

BACKGROUND: Automated detection of heart murmurs with computer-aided auscultation is not yet in clinical routine use. Aim of this study was to test sensitivity and specificity of a novel prototype algorithm in automated detection of heart murmurs from digitally recorded phonocardiograms in neonates admitted at the Neonatal Intensive Care Unit. METHODS: In a prospective pilot observational study from November 2012 to December 2013 auscultations by pediatricians and computer aided auscultation were performed within 12 hours of neonatal echocardiography. Echocardiography was defined as pathological when resulting in any clinical consequences or causing murmur. Phonocardiograms and auscultation were defined as pathological if a murmur was detected. Phonocardiograms were analyzed offline with a novel algorithm prototype (CSD Labs, Graz, Austria) for detection of murmurs in neonates in a first run and with an optimized algorithm in a second run and were compared with echocardiography. Sensitivity and specificity of auscultation by pediatrician and computer aided auscultation were analyzed. RESULTS: Thirty-six neonates (gestational age: 36±3 weeks) were included. Twenty-three (64%) neonates had pathological or murmur causing findings in echocardiography (positive echocardiography). Sensitivity and specificity of auscultation by pediatrician were 17% and 100%, respectively. In comparison to auscultation by pediatrician sensitivity of first run and second run were significantly higher with 70% and 83%, respectively. Specificity of first run and second run were 77% and 85%, respectively. CONCLUSIONS: Phonocardiogram analysis using the novel algorithm prototype had a higher sensitivity than auscultation by pediatrician in detecting positive echocardiography findings in neonates.

Haemodynamic effects of prenatal caffeine on the cardiovascular transition in ventilated preterm lambs.

BACKGROUND: Caffeine is routinely given to preterm infants hours after birth to treat apnea of prematurity. In view of it's success, earlier administration in the delivery room is being considered, but little is known about how caffeine may effect the cardiovascular changes during the fetal to neonatal transition. Our aim was to determine the effect of prenatal caffeine administration on haemodynamic parameters in ventilated preterm lambs immediately after birth. METHODS: Catheters (carotid artery and jugular vein) and ultrasonic flow probes (pulmonary artery and carotid artery) were implanted in preterm lambs (~126 ±2 days of gestation; term is 147 days), immediately before delivery by caesarean section. Before the cord was clamped, lambs were intubated and a caffeine (10mg/kg caffeine-base; n = 9) or saline (n = 5) infusion was given intravenously to the ewe and lamb over a 15-minute period. Two minutes after clamping the cord, ventilation commenced with a sustained inflation (35 cm H2O for 30 seconds) followed by ventilation for 30 minutes (target tidal volume of 6-8ml/kg). RESULTS: Blood gas parameters and rectal body temperature were not different between the two groups. Changes in pulmonary blood flow (PBF) and carotid blood flow (CBF) did not differ significantly between groups. PBF increased significantly after ventilation onset in both groups (caffeine p = 0.022, saline p <0.001) and remained elevated thereafter. CBF did not increase but decreased after SI in the caffeine group. Blood pressure, heart rate, and peripheral oxygen saturation did not differ between groups at any stage of the study. CONCLUSION: Prenatal caffeine infusion had no significant effect on acute haemodynamic parameters in ventilated preterm lambs during the cardiorespiratory transition.

Cerebral Blood Volume During Neonatal Transition in Term and Preterm Infants With and Without Respiratory Support.

Background: Recently, we demonstrated that in healthy newborn infants cerebral blood volume (CBV) was decreasing continuously after birth. We hypothesized that this was due to the increase in oxygen delivery to the brain during neonatal transition. Thus delayed cerebral oxygen delivery in infants in need for respiratory support (RS) during postnatal stabilization might influence changes in CBV. Objective: Aim of the study was to evaluate transitional changes in CBV immediately after birth in term and preterm infants with and without need of RS. Methods: We performed a post-hoc analysis of data collected as primary and secondary outcome parameters in prospective observational studies and randomized controlled trials at the Medical University of Graz (Austria). NIRS measurements by using "NIRO 200-NX" (Hamamatsu, Japan) were carried out over the first 15 min after birth in term and preterm infants delivered by cesarean section with and without requirement for RS. Results: In 204 neonates, we observed a significant decrease in CBV within the first 15 min after birth (p < 0.001) with a trend toward smaller ΔCBV in neonates receiving RS (p = 0.097) compared to neonates without RS. Differences of ΔCBV between groups reached statistically significance (p < 0.05) at minutes 2, 6, and 7, and showed a trend (p < 0.1) at minutes 3, 4, and 5. After adjusting for gestational age, these differences became smaller and failed to reach significance. Conclusions: We observed a significant decrease of CBV in term and preterm infants with and without RS. Interestingly, ΔCBV was smaller in the first 7 min in neonates with RS reaching statistically significance (p < 0.05) at minutes 2, 6, and 7. This study cannot differentiate, whether RS itself or the condition leading to requirement for RS is responsible for the observed CBV behavior.

Near-infrared spectroscopy monitoring during immediate transition after birth: time to obtain cerebral tissue oxygenation.

Feasibility of cerebral tissue oxygenation measurements immediately after birth has been published starting with first values 2 min after birth. Aim of this study was to evaluate, the time periods from birth and from arrival at the resuscitation table to obtain the first cerebral tissue oxygenation values with two different near infrared spectroscopy (NIRS) devices. The present study is an analysis of exploratory parameters of two prospective observational studies. Cerebral tissue oxygen saturation was measured by the NIRO 200NX measuring "cerebral-tissue-oxygenation-index" (cTOI) or the INVOS5100C measuring "cerebral-regional-oxygen-saturation" (crSO2). Four time periods (T) were defined: T1 birth to arrival at resuscitation table, T2 arrival to application of NIRS sensor, T3 application to first displayed cTOI or crSO2 value, and T4 from arrival at resuscitation table to first displayed values. Additionally, we compared first displayed values of cTOI and crSO2. Thirty neonates were included. Twenty-four were term and six late-preterm neonates. Fifteen neonates measured with NIRO were compared to 15 measured with INVOS. T1 was 49 (6-163) s with NIRO versus 59 (15-87) s with INVOS, T2 14 (4-20) s versus 12 (15-18) s, T3 33 (13-138) s versus 17 (6-290) s and T4 46 (20-153) s and 34 (14-300) s. The first displayed value tended to be higher for cTOI [54% (18-80)] compared to crSO2 [35% (15-87)]. There were no significant differences between devices in time periods and first values displayed. Cerebral tissue oxygenation can be measured within 1 min after arriving at the resuscitation table in term and preterm neonates after birth without difference between devices.

Laryngeal closure impedes non-invasive ventilation at birth.

BACKGROUND: Non-invasive ventilation is sometimes unable to provide the respiratory needs of very premature infants in the delivery room. While airway obstruction is thought to be the main problem, the site of obstruction is unknown. We investigated whether closure of the larynx and epiglottis is a major site of airway obstruction. METHODS: We used phase contrast X-ray imaging to visualise laryngeal function in spontaneously breathing premature rabbits immediately after birth and at approximately 1 hour after birth. Non-invasive respiratory support was applied via a facemask and images were analysed to determine the percentage of the time the glottis and the epiglottis were open. HYPOTHESIS: Immediately after birth, the larynx is predominantly closed, only opening briefly during a breath, making non-invasive intermittent positive pressure ventilation (iPPV) ineffective, whereas after lung aeration, the larynx is predominantly open allowing non-invasive iPPV to ventilate the lung. RESULTS: The larynx and epiglottis were predominantly closed (open 25.5%±1.1% and 17.1%±1.6% of the time, respectively) in pups with unaerated lungs and unstable breathing patterns immediately after birth. In contrast, the larynx and the epiglottis were mostly open (90.5%±1.9% and 72.3%±2.3% of the time, respectively) in pups with aerated lungs and stable breathing patterns irrespective of time after birth. CONCLUSION: Laryngeal closure impedes non-invasive iPPV at birth and may reduce the effectiveness of non-invasive respiratory support in premature infants immediately after birth.

Influence of ductus arteriosus on peripheral muscle oxygenation and perfusion in neonates.

OBJECTIVE: In neonates, a patent ductus arteriosus (DA) may be associated with severe complications. We used near-infrared spectroscopy (NIRS) with venous occlusion to investigate the influence of an open DA on peripheral muscle oxygenation/perfusion in preterm neonates. APPROACH: We analyzed secondary outcome parameters collected as part of prospective observational studies. NIRS measurements were performed between the first and third day of life. Arterial oxygen saturation (SaO2) and heart rate (HR) were monitored by pulse oximetry on the ipsilateral foot. Venous occlusion was performed with a blood pressure cuff on the thigh. Tissue oxygenation index (TOI), hemoglobin flow (Hbflow), oxygen delivery (DO2), oxygen consumption (VO2), mixed venous oxygenation (SvO2), and fractional oxygen extraction (FOE) were assessed. Echocardiography was performed within plus/minus 6 h from NIRS measurements. MAIN RESULTS: Twenty-eight neonates were included. In neonates with open DA (n = 15), the FOE was significantly higher (p = 0.046). DA diameter correlated negatively with SvO2 (r = -0.413, p = 0.032) and positively with FOE (r = 0.417, p = 0.030). In neonates with open DA, SaO2 was significantly lower (p = 0.041). DA diameter correlated negatively with SaO2 (r = -0.377, p = 0.048) and positively with HR (r = 0.489, p = 0.010). SIGNIFICANCE: Our results showed that an open DA influences peripheral muscle oxygenation in preterm neonates.

Vagal denervation inhibits the increase in pulmonary blood flow during partial lung aeration at birth.

KEY POINTS: Lung aeration at birth significantly increases pulmonary blood flow, which is unrelated to increased oxygenation or other spatial relationships that match ventilation to perfusion. Using simultaneous X-ray imaging and angiography in near-term rabbits, we investigated the relative contributions of the vagus nerve and oxygenation to the increase in pulmonary blood flow at birth. Vagal denervation inhibited the global increase in pulmonary blood flow induced by partial lung aeration, although high inspired oxygen concentrations can partially mitigate this effect. The results of the present study indicate that a vagal reflex may mediate a rapid global increase in pulmonary blood flow in response to partial lung aeration. ABSTRACT: Air entry into the lungs at birth triggers major cardiovascular changes, including a large increase in pulmonary blood flow (PBF) that is not spatially related to regional lung aeration. To investigate the possible underlying role of a vagally-mediated stimulus, we used simultaneous phase-contrast X-ray imaging and angiography in near-term (30 days of gestation) vagotomized (n = 15) or sham-operated (n = 15) rabbit kittens. Rabbits were imaged before ventilation, when one lung was ventilated (unilateral) with 100% nitrogen (N2 ), air or 100% oxygen (O2 ), and after all kittens were switched to unilateral ventilation in air and then ventilation of both lungs using air. Compared to control kittens, vagotomized kittens had little or no increase in PBF in both lungs following unilateral ventilation when ventilation occurred with 100% N2 or with air. However, relative PBF did increase in vagotomized animals ventilated with 100% O2 , indicating the independent stimulatory effects of local oxygen concentration and autonomic innervation on the changes in PBF at birth. These findings demonstrate that vagal denervation inhibits the previously observed increase in PBF with partial lung aeration, although high inspired oxygen concentrations can partially mitigate this effect.

The timing of umbilical cord clamping at birth: physiological considerations.

While it is now recognized that umbilical cord clamping (UCC) at birth is not necessarily an innocuous act, there is still much confusion concerning the potential benefits and harms of this common procedure. It is most commonly assumed that delaying UCC will automatically result in a time-dependent net placental-to-infant blood transfusion, irrespective of the infant's physiological state. Whether or not this occurs, will likely depend on the infant's physiological state and not on the amount of time that has elapsed between birth and umbilical cord clamping (UCC). However, we believe that this is an overly simplistic view of what can occur during delayed UCC and ignores the benefits associated with maintaining the infant's venous return and cardiac output during transition. Recent experimental evidence and observations in humans have provided compelling evidence to demonstrate that time is not a major factor influencing placental-to-infant blood transfusion after birth. Indeed, there are many factors that influence blood flow in the umbilical vessels after birth, which depending on the dominating factors could potentially result in infant-to-placental blood transfusion. The most dominant factors that influence umbilical artery and venous blood flows after birth are lung aeration, spontaneous inspirations, crying and uterine contractions. It is still not entirely clear whether gravity differentially alters umbilical artery and venous flows, although the available data suggests that its influence, if present, is minimal. While there is much support for delaying UCC at birth, much of the debate has focused on a time-based approach, which we believe is misguided. While a time-based approach is much easier and convenient for the caregiver, ignoring the infant's physiology during delayed UCC can potentially be counter-productive for the infant.

Low cerebral activity and cerebral oxygenation during immediate transition in term neonates-A prospective observational study.

AIM: To analyze whether in term neonates during immediate transition after birth low cerebral activity measured by amplitude-integrated EEG (aEEG) is linked to cerebral regional oxygen saturation (crSO2) measured by near-infrared spectroscopy (NIRS). Additionally, the cerebral fractional tissue oxygen extraction (cFTOE) was calculated to analyze whether cerebral activity is linked to cFTOE. METHODS: A total of 244 term neonates delivered by primary cesarean section were studied. In addition to routine monitoring with pulse oximetry, aEEG and NIRS measurements were performed during the first 15min after birth. The mean minimum (Vmin) and maximum (Vmax) amplitude of the cerebral activity as well as crSO2 and cFTOE for each minute was determined. Neonates with initial Vmin<5µV or Vmax<10µV, which normalized during transition (study group) were compared to neonates with normal aEEG values throughout the whole monitoring period (control group). RESULTS: 9 neonates fulfilled inclusion criteria to the study group and were compared to 50 neonates in the control group. Vmin, Vmax, crSO2, SpO2 and cFTOE were compared from the 4th to 15thmin after birth. During our study period, Vmin and Vmax were significantly lower in the study group than in the control group. crSO2 was significantly lower in the study group until minute 11, dropping below the 10th centile in minute 8. cFTOE was significantly higher in the study group until minute 10, rising above the 90th centile in minutes 8 and 9. SpO2 was within normal ranges in both groups. crSO2 and cFTOE were within normal ranges in the control group. CONCLUSION: The present study demonstrates that neonates with initially low cerebral activity during immediate transition after birth concurrently showed low crSO2 (<10th percentile), but increased cerebral oxygen extraction (cFTOE>90th percentile). Cerebral monitoring with aEEG and NIRS might provide useful information on the neonates' condition during immediate transition.