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

Reference Ranges for Regional Cerebral Oxygen Saturation with Masimo O3 after Birth and Differences with Other Devices

OBJECTIVE

 Cerebral oximetry using near-infrared spectroscopy (NIRS) is a noninvasive optical technology widely used in neonatology. The present study aimed to define reference ranges for cerebral tissue oxygen saturation (crSO2) with a new four-wavelength NIRS device, Masimo O3 oximeter, during immediate transition after birth and compare values with those obtained previously with NIRO 200NX®.

STUDY DESIGN

 This was a prospective observational study using Masimo O3 device to measure crSO2 and regional cerebral fractional tissue oxygen extraction (cFTOE) in healthy term newborns delivered by primary cesarean section, during the 15 minutes after cord clamping. The neonates who required any medical support were excluded. The NIRS sensor was placed on the right forehead. Peripheral oxygen saturation and heart rate were continuously measured by pulse oximetry. Previous studies which established centiles for crSO2 with NIRO 200NX were used for comparison.

RESULTS

 A total of 44 newborns were included. The median crSO2 and cFTOE (interquartile range) at 2, 5, and 7 minutes was 54% (49-54), 71% (64-86), and 79% (73-84) and 0,25 (0,18-0,33), 0,19 (0,15-0,23), and 0,16 (0,12-0,21), respectively, with no further changes afterwards. The crSO2 measurements were significantly higher with Masimo O3 compared with NIRO-200NX.

CONCLUSION

 The present observational study presented reference ranges for crSO2 and cFTOE measured with Masimo O3 oximeter during the immediate neonatal transition. Values obtained with O3 were higher than those obtained with other oximeters. For this reason, crSO2 is device-specific so there must be known reference values for each oximeter to define therapeutic interventions based on crSO2 and assess cerebral oxygenation in clinical studies.

KEY POINTS

· Masimo O3 uses four wavelengths to measure regional oxygen saturation value.. · O3 values of crSO2 and cFTOE differ with other neonatal oximeters at birth.. · Knowledge of reference range of O3 at birth is essential to guide resuscitation..

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.

Comparison of the Effects of Anaesthesia Methods Used in Caesarean Delivery on Neonatal Cerebral and Renal Oxygenation: A Randomised Controlled Trial

Background: During a newborn's adaptation to extrauterine life, many changes take place that are influenced by various factors. The type of delivery and anaesthesia strategy utilised during labour can modify these adaptive modifications. In this regard, this study was designed to compare the effects of general and spinal anaesthesia on cerebral and renal oxygenation after elective caesarean deliveries. Methods: This randomised controlled study comprised sixty parturient women who were over 18 years old and had a gestational age between 37 and 41 weeks. All participants had an ASA (American Society of Anesthesiologists) classification of II. Neonatal cerebral (CrSO2) and renal (RrSO2) regional oxygen saturations were assessed using near-infrared spectroscopy. Additionally, the 1st-5th min Apgar scores, preductal and postductal peripheral oxygen saturation (SpO2), and perfusion index were recorded in both the general anaesthesia and spinal anaesthesia groups. Results: There was no statistically significant difference between the two groups in terms of CrSO2 or RrSO2 values. The values of CrSO2 and RrSO2 in both groups showed a significant rise from the 10th to the 15th min, respectively. Conclusions: General and spinal anaesthesia techniques used for cesarean delivery have similar effects on neonatal cerebral and renal oxygenation.

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.

Impact of Carbon Dioxide on Cerebral Oxygenation and Vital Parameters in Stable Preterm and Term Infants Immediately after Birth

INTRODUCTION

Carbon dioxide (pCO2) induces changes in the tone of cerebral vessels. The aim of the present study was to evaluate the impact of pCO2 on cerebral regional tissue oxygen saturation (crSO2), cerebral fractional tissue oxygen extraction (cFTOE), and cerebral tissue oxygen extraction (cTOE), measured with near-infrared spectroscopy (NIRS), in preterm and term infants 15 min after birth.

METHODS

Post hoc analyses of secondary outcome parameters of prospective observational studies were performed. Stable preterm and term infants with cerebral NIRS monitoring (INVOS 5100C) until minute 15 after birth and a blood gas analysis, performed between minutes 14-18 after birth, were included. Heart rate (HR) and arterial oxygen saturation (SpO2) were recorded. pCO2 was correlated with crSO2, cFTOE, cTOE, SpO2, HR, and partial pressure of oxygen (pO2).

RESULTS

Eleven preterm infants with a median (IQR) gestational age of 34.8 (32.7-36.1) weeks were analyzed. Mean ± SD pCO2 was 53.5 ± 4.2 mm Hg. At minute 15 after birth, crSO2 was 82.6 (74.3-91.3)%, cFTOE 0.15 ± 0.09, cTOE 14.6 ± 8.4%, SpO2 97.4 ± 2.1%, and HR 152 (136-167) bpm. pCO2 correlated negatively with crSO2 (p = 0.012) and positively with cFTOE (p = 0.035) and cTOE (p = 0.037). Eighty-four term infants with a gestational age of 39.0 (38.5-38.9) weeks were analyzed. pCO2 was 53.5 ± 6.3 mm Hg. At minute 15 after birth, crSO2 was 84.4 (80.8-85.1)%, cFTOE 0.14 ± 0.08, cTOE 13.6 ± 7.9%, SpO2 96.5 ± 2.6%, and HR 155 (153-163) bpm. pCO2 did only negatively correlate with pO2 (p = 0.034) in term infants.

CONCLUSION

In preterm infants, higher pCO2 was associated with lower crSO2 and higher cFTOE/cTOE. In term infants, no associations were observed. The present findings suggest that the vasodilatative effect of pCO2 is less pronounced in preterm infants during immediate postnatal transition.

Correlation between arterial blood pressures and regional cerebral oxygen saturation in preterm neonates during postnatal transition-an observational study

OBJECTIVE

To assess whether blood pressure (systolic (SABP), diastolic (DABP), and mean arterial blood pressure (MABP) and cerebral-regional-oxygen-saturation (crSO2) and cerebral-fractional-tissue-oxygen-extraction (cFTOE) are associated after immediate fetal-to-neonatal transition in preterm neonates with and without respiratory support.

STUDY DESIGN

Post-hoc analyses of secondary outcome parameters of prospective observational studies were performed. We included moderate and late preterm neonates with and without respiratory support with cerebral NIRS monitoring (INVOS 5100c) and an oscillometric blood pressure measurement at minute 15 after birth. Heart rate (HR) and arterial oxygen saturation (SpO2) were monitored routinely. Blood pressure values were correlated with crSO2 and cFTOE.

RESULTS

47 preterm neonates with NIRS measurements and blood pressure measurement during immediate transition after birth were included. Twenty-five preterm neonates (gestational age: 34.4±1.6 weeks) received respiratory support. In these neonates crSO2 correlated significantly positively with systolic blood pressure (SABP; r = 0.46, p = 0.021), diastolic blood pressure (DABP; r = 0.51, p = 0.009) and, mean arterial pressure (MABP; r = 0.48, p = 0.015). cFTOE correlated significantly negatively with SABP (r = -0.44, p = 0.027), DABP (r = -0.49, p = 0.013) and mean MABP (r = -0.44, p = 0.029). Twenty-two preterm neonates (gestational age: 34.5 ± 1.5 weeks) did not receive respiratory support. In those neonates, neither crSO2 nor cFTOE correlated with blood pressure.

CONCLUSION

In compromised moderate and late preterm neonates with respiratory support, both, crSO2 and cFTOE correlated with blood pressure. These findings suggest that passive pressure-dependent cerebral perfusion was present in preterm neonates with respiratory support, indicating an impaired cerebral autoregulation in those compromised preterm neonates.

Cerebral oxygen saturation and cerebrovascular instability in newborn infants with congenital heart disease compared to healthy controls

Objective

Infants with Congenital Heart Disease (CHD) are at risk for developmental delays, though the mechanisms of brain injury that impair development are unknown. Potential causes could include cerebral hypoxia and cerebrovascular instability. We hypothesized that we would detect significantly reduced cerebral oxygen saturation and greater cerebrovascular instability in CHD infants compared to the healthy controls.

Methods

We performed a secondary analysis on a sample of 43 term infants (28 CHD, 15 healthy controls) that assessed prospectively in temporal cross-section before or at 12 days of age. CHD infants were assessed prior to open-heart surgery. Cerebral oxygen saturation levels were estimated using Near-Infrared Spectroscopy, and cerebrovascular stability was assessed with the response of cerebral oxygen saturation after a postural change (supine to sitting).

Results

Cerebral oxygen saturation was 9 points lower in CHD than control infants in both postures (β = -9.3; 95%CI = -17.68, -1.00; p = 0.028), even after controlling for differences in peripheral oxygen saturation. Cerebrovascular stability was significantly impaired in CHD compared to healthy infants (β = -2.4; 95%CI = -4.12, -.61; p = 0.008), and in CHD infants with single ventricle compared with biventricular defects (β = -1.5; 95%CI = -2.95, -0.05; p = 0.04).

Conclusion

CHD infants had cerebral hypoxia and decreased cerebral oxygen saturation values following a postural change, suggesting cerebrovascular instability. Future longitudinal studies should assess the associations of cerebral hypoxia and cerebrovascular instability with long-term neurodevelopmental outcomes in CHD infants.

Higher preoperative Qp/Qs ratio is associated with lower preoperative regional cerebral oxygen saturation in children with ventricular septal defect

PURPOSE

The relationship between regional cerebral oxygen saturation (rSO₂) and the amount of left-to-right shunt in ventricular septal defect (VSD) patients has not yet been investigated. The purpose of this study was to identify the association of preoperative pulmonary to systemic blood flow (Qp/Qs) ratio and preoperative rSO₂ in patients with VSD.

METHODS

We retrospectively evaluated 49 VSD surgical closure candidates at a single institution. Preoperative Qp/Qs ratio was compared with rSO₂ measurements at the time of VSD closure surgery.

RESULTS

Forty-nine were eligible for the final analysis. The median age at surgery was 6 (interquartile range [IQR]: 3, 12) months, and 36.7% were male. Atrial septal defects coexisted in 51.0%. There were no genetic abnormalities except trisomy 21 in 32.6% of the patients. Pulmonary hypertension was found in 42.8%. The median Qp/Qs ratio, calculated based on catheter testing results before the surgery, was 2.7 (IQR: 2.1, 3.7). Postoperative rSO₂ was significantly higher than preoperative values (52.2 ± 12.9, 63.5 ± 13.1%, p < 0.001). There was an inverse relationship of Qp/Qs and preoperative cerebral rSO₂ (r = - 0.11, p = 0.02).

CONCLUSION

A higher Qp/Qs ratio was associated with a lower preoperative cerebral rSO₂ in pediatric patients with VSD.

Increased Risk for Cerebral Hypoxia During Immediate Neonatal Transition After Birth in Term Neonates Delivered by Caesarean Section With Prenatal Tobacco Exposure

Introduction: Maternal tobacco smoking during pregnancy is a global health problem leading to an increased risk for fetal and neonatal morbidities. So far, there are no data of the potential impact of maternal smoking during pregnancy on the most vulnerable period after birth - the immediate postnatal transition. The aim of the present study was therefore, to compare cerebral oxygenation during immediate postnatal transition in term neonates with and without prenatal tobacco exposure. Methods: Included in this post-hoc analysis were healthy term neonates, with measurements of cerebral oxygenation (INVOS 5100C) during the first 15 min after birth, and for whom information on maternal smoking behavior during pregnancy was available. Neonates with prenatal tobacco exposure (smoking group) were matched 1:1 according to gestational age (±1 week), birth weight (±100 grams) and hematocrit (±5 %) to neonates without (non-smoking group). Cerebral regional tissue oxygen saturation (crSO₂), cerebral fractional tissue oxygen extraction (cFTOE), arterial oxygen saturation (SpO₂) and heart rate (HR) within the first 15 min after birth were compared between the two groups. Results: Twelve neonates in the smoking group with a median (IQR) gestational age of 39.1 (38.8-39.3) weeks and a birth weight of 3,155 (2,970-3,472) grams were compared to 12 neonates in the non-smoking group with 39.1 (38.7-39.2) weeks and 3,134 (2,963-3,465) grams. In the smoking group, crSO₂ was significantly lower and cFTOE significantly higher until min 5 after birth. HR was significantly higher in the smoking group in min 3 after birth. Beyond this period, there were no significant differences between the two groups. Conclusion: Cerebral oxygenation within the first 5 min after birth was compromised in neonates with prenatal tobacco exposure. This observation suggests a higher risk for cerebral hypoxia immediately after birth due to fetal tobacco exposure.

Cerebral Oxygen Changes in Neonates During Immediate Transition After Birth and Early Life: An Observational Study

Purpose

The physiologic transition from a fetus to a neonate is composed of a series of complex processes that include changes in cerebral tissue oxygenation saturation (cSO₂). Monitoring this process is of great importance. This study aimed to define the cSO₂ reference interval in neonates without medical support, extending the measurements until 1 hour after birth, and to determine the incidence of abnormally low or high regional cerebral oxygenation during the neonatal transition.

Patients and Methods

A total of 418 neonates delivered by cesarean section were enrolled. Near-infrared spectroscopy was used to monitor cerebral oxygenation.

Results

We found that cSO₂ of the non-oxygen-inhaled intrathecal anesthesia in neonates without medical support increased from about 49.0% in the second minute. Most of them reached cSO₂ relative stabilization at 55.7-81.0% between 7 and 8 minutes after birth. One hour after birth, newborn cSO₂ was maintained at 78.0-87.0%. The low cSO₂ rate among babies born under intrathecal anesthesia with and without maternal oxygen inhalation during cesarean sections was approximately 4.5% and 9.0%, respectively.

Conclusion

We reported the trend in cSO₂ from 2 minutes after birth to 1 hour in the neonatal nursing room and determined the incidence of abnormal regional cSO₂ during this neonatal transition period. Anesthesiologists should pay special attention to the risk of cSO₂ abnormalities in newborns when managing pregnant women with comorbidities.

Nasal high-frequency percussive ventilation vs nasal continuous positive airway pressure in newborn infants respiratory distress: A cross over clinical trial

OBJECTIVE

To determine if nasal high-frequency percussive ventilation (nHFPV) to manage neonatal respiratory distress decreases the regional cerebral oxygen saturation (rScO₂ ) compared to nasal continous positive airway pressure (nCPAP).

STUDY DESIGN

A prospective, randomized, monocentric, open-label, noninferiority crossover trial. Newborns of gestational age (GA) ≥ 33 weeks exhibiting persistent respiratory distress after 10 minutes of life were treated with nHFPV and nCPAP, in succession and in random order. The primary endpoint was the mean rScO₂ , as revealed by near-infrared spectroscopy (NIRS).

RESULTS

Forty-nine newborns were randomized; the mean GA and birth weight was 36.4 ± 1.9 weeks and 2718 ± 497 g. The mean rScO₂ difference during the last 5 minutes of each ventilation mode (nHFPV minus nCPAP) was -0.7 ± 5.4% (95% confidence interval (CI) -2.25; 0.95%).

CONCLUSION

In our study on newborns of GA ≥33 weeks treated for respiratory distress, cerebral oxygenation via nHFPV was not inferior to nCPAP.

NIRS in the fetal to neonatal transition and immediate postnatal period

Near-infrared spectroscopy (NIRS) offers the non-invasive continuous monitoring of cerebral oxygenation and perfusion. Cerebral regional oxygen (crSO2) measured via NIRS represents a mixed tissue saturation value, thus enabling information on the balance of cerebral oxygen delivery and oxygen consumption. Cerebral oxygenation is influenced by pulse oximeter saturation (SpO2), hemoglobin content, and cerebral blood flow. Furthermore, cerebral oxygenation is dependent on metabolic parameters, cardio circulatory parameters, perinatal- and postnatal interventions. Reference ranges for healthy term born and late preterm infants have already been published. It is feasible to increase crSO2 values above the 10th percentile by guiding medical support during neonatal to fetal transition. Guiding oxygen supply based on NIRS monitoring in addition to SpO2 monitoring showed that a reduction of the burden of cerebral hypoxia was possible. A currently ongoing study will give further information whether additional NIRS monitoring guiding medical support during neonatal to fetal transition is effective in improving neonatal outcome.

Comparison of cut and intact cord milking regarding cerebral oxygenation, hemodynamic and hematological adaptation of term infants

OBJECTIVE

Although both delayed umbilical cord clamping and intact umbilical cord milking (I-UCM) provide the effective placental transfusion at birth, these procedures may not be used in neonates needing resuscitation. The aim of this study is to investigate the effect of cut umbilical cord milking (C-UCM), which permits resuscitation during an immediate transition period (ITP).

METHODS

Sixty-two healthy term infants were randomly divided into C-UCM and I-UCM groups at birth. Approximately 30-cm length of cord was milked towards the baby 2-4 times within 20 seconds after birth in both C-UCM and I-UCM groups while the umbilical cord was cut in the former, and intact in the latter. Heart rate, arterial oxygen saturation (SpO₂), cerebral regional oxygen saturation (crSO₂) (2nd-15th min), blood pressure (BP) (within 15-30 min), residual placental blood volume (RPBV), and hemoglobin levels (at the sixth hour) were monitored during ITP.

RESULTS

There were no significant differences in terms of mean gestational age (w) [(39.0 ± 1.2) versus (38.8 ± 1.1)], birth weight (g) [(3351.45 ± 254.30) versus (3256.94 ± 285.52)], Apgar scores at the 5th min (10 ± 0 versus 10 ± 0), first breathing time (sec) (5.4 ± 3.8 versus 5.7 ± 4.1), SpO₂, crSO₂, BP (mmHg) [(52.9 ± 6.9) versus (51.8 ± 5.7)], hemoglobin levels (g/dl) [(17.7 ± 1.8) versus (18.4 ± 1.4)], and RPBV (ml/kg) [(23.9 ± 4.7) versus (22.9 ± 5.4)] between C-UCM and I-UCM groups (p > .05).

CONCLUSION

This study showed that C-UCM is as effective as I-UCM on cerebral oxygenation, hemodynamic and hematological adaptation of term infants in ITP. We suggest that C-UCM can provide additional placental transfusion in term neonates exposed to early cord clamping.

Cerebral regional tissue Oxygen Saturation to Guide Oxygen Delivery in preterm neonates during immediate transition after birth (COSGOD III): an investigator-initiated, randomized, multi-center, multi-national, clinical trial on additional cerebral tissue oxygen saturation monitoring combined with defined treatment guidelines versus standard monitoring and treatment as usual in premature infants during immediate transition: study protocol for a randomized controlled trial

BACKGROUND

Transition immediately after birth is a complex physiological process. The neonate has to establish sufficient ventilation to ensure significant changes from intra-uterine to extra-uterine circulation. If hypoxia or bradycardia or both occur, as commonly happens during immediate transition in preterm neonates, cerebral hypoxia-ischemia may cause perinatal brain injury. The primary objective of the COSGOD phase III trial is to investigate whether it is possible to increase survival without cerebral injury in preterm neonates of less than 32 weeks of gestation by targeting cerebral tissue oxygen saturation (crSO2) using specified clinical treatment guidelines during the immediate transition period after birth (the first 15 min) in addition to the routine monitoring of arterial oxygen saturation (SpO2) and heart rate (HR).

METHODS/DESIGN

COSGOD III is an investigator-initiated, randomized, multi-center, multi-national, phase III clinical trial. Inclusion criteria are neonates of less than 32 weeks of gestation, decision to provide full life support, and parental informed consent. Exclusion criteria are severe congenital malformations of brain, heart, lung, or prenatal cerebral injury or a combination of these. The premature infants will be randomly assigned to study or control groups. Both groups will have a near-infrared spectroscopy (NIRS) device (left frontal), pulse oximeter (right palm/wrist), and electrocardiogram placed immediately after birth. In the study group, the crSO2, SpO2, and HR readings are visible, and the infant will receive treatment in accordance with defined treatment guidelines. In the control group, only SpO2 and HR will be visible, and the infant will receive routine treatment. The intervention period will last for the first 15 min after birth during the immediate transition period and resuscitation. Thereafter, each neonate will be followed up for primary outcome to term date or discharge. The primary outcome is mortality or cerebral injury (or both) defined as any intra-ventricular bleeding or cystic periventricular leukomalacia (or both). Secondary outcomes are neonatal morbidities.

DISCUSSION

crSO2 monitoring during immediate transition has been proven to be feasible and improve cerebral oxygenation during immediate transition. The additional monitoring of crSO2 with dedicated interventions may improve outcome of preterm neonates as evidenced by increased survival without cerebral injury.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03166722 . Registered March 5, 2017.

Haemodynamic Instability and Brain Injury in Neonates Exposed to Hypoxia⁻Ischaemia

Brain injury in the asphyxic newborn infant may be exacerbated by delayed restoration of cardiac output and oxygen delivery. With increasing severity of asphyxia, cerebral autoregulatory responses are compromised. Further brain injury may occur in association with high arterial pressures and cerebral blood flows following the restoration of cardiac output. Initial resuscitation aims to rapidly restore cardiac output and oxygenation whilst mitigating the impact of impaired cerebral autoregulation. Recent animal studies have indicated that the current standard practice of immediate umbilical cord clamping prior to resuscitation may exacerbate injury. Resuscitation prior to umbilical cord clamping confers several haemodynamic advantages. In particular, it retains the low-resistance placental circuit that mitigates the rebound hypertension and cerebrovascular injury. Prolonged cerebral hypoxia⁻ischaemia is likely to contribute to further perinatal brain injury, while, at the same time, tissue hyperoxia is associated with oxidative stress. Efforts to monitor and target cerebral flow and oxygen kinetics, for example, using near-infrared spectroscopy, are currently being evaluated and may facilitate development of novel resuscitation approaches.

Cerebral Tissue Oxygenation during Immediate Neonatal Transition and Resuscitation

This article provides a review of cerebral tissue oxygenation during immediate transition after birth in human neonates. Recommended routine monitoring, especially if resuscitation is needed, during this period includes arterial oxygen saturation and heart rate measured by pulse oximetry and electrocardiogram. However, there is increasing interest to monitor in addition with near-infrared spectroscopy (NIRS) the oxygenation of the brain. There is a different pattern of increase between cerebral tissue oxygenation and arterial oxygen saturation during the immediate transition, with cerebral tissue oxygenation reaching a plateau faster than arterial oxygen saturation. Differences can be explained, since cerebral tissue oxygenation is not only affected by arterial oxygen saturation but also by cerebral blood flow, hemoglobin content, and cerebral oxygen consumption. Normal values have already been established for different devices, gestational ages, and modes of delivery in neonates without any medical support. Cerebral hypoxia during immediate transition might cause brain damage. In preterm neonates with cerebral hemorrhage evolving in the first week after birth, the cerebral tissue oxygenation is already lower in the first minutes after birth compared to preterm neonates without cerebral hemorrhage. Using cerebral NIRS in combination with intervention guidelines has been shown to reduce the burden of cerebral hypoxia in preterm neonates. Cerebral tissue oxygenation during immediate transition seems to have an impact on outcome, whereby NIRS monitoring is feasible and has the advantage of continuous, non-invasive recording. The impact of NIRS monitoring and interventions on short- and long-term outcomes still need to be evaluated.

Fetal Physiology and the Transition to Extrauterine Life

The physiology of the fetus is fundamentally different from the neonate, with both structural and functional distinctions. The fetus is well-adapted to the relatively hypoxemic intrauterine environment. The transition from intrauterine to extrauterine life requires rapid, complex, and well-orchestrated steps to ensure neonatal survival. This article explains the intrauterine physiology that allows the fetus to survive and then reviews the physiologic changes that occur during the transition to extrauterine life. Asphyxia fundamentally alters the physiology of transition and necessitates a thoughtful approach in the management of affected neonates.

Pregnancy at high altitude in the Andes leads to increased total vessel density in healthy newborns

The developing human fetus is able to cope with the physiological reduction in oxygen supply occurring in utero. However, it is not known if microvascularization of the fetus is augmented when pregnancy occurs at high altitude. Fifty-three healthy term newborns in Puno, Peru (3,840 m) were compared with sea-level controls. Pre- and postductal arterial oxygen saturation (SpO2) was determined. Cerebral and calf muscle regional tissue oxygenation was measured using near infrared spectroscopy (NIRS). Skin microcirculation was noninvasively measured using incident dark field imaging. Pre- and postductal SpO2 in Peruvian babies was 88.1 and 88.4%, respectively, which was 10.4 and 9.7% lower than in newborns at sea level (P < 0.001). Cerebral and regional oxygen saturation was significantly lower in the Peruvian newborns (cerebral: 71.0 vs. 74.9%; regional: 68.5 vs. 76.0%, P < 0.001). Transcutaneously measured total vessel density in the Peruvian newborns was 14% higher than that in the newborns born at sea level (29.7 vs. 26.0 mm/mm(2); P ≤ 0.001). This study demonstrates that microvascular vessel density in neonates born to mothers living at high altitude is higher than that in neonates born at sea level.

Enhanced Monitoring of the Preterm Infant during Stabilization in the Delivery Room

Monitoring of preterm infants in the delivery room (DR) remains limited. Current guidelines suggest that pulse oximetry should be available for all preterm infant deliveries, and that if intubated a colorimetric carbon dioxide detector should provide verification of correct endotracheal tube placement. These two methods of assessment represent the extent of objective monitoring of the newborn commonly performed in the DR. Monitoring non-invasive ventilation effectiveness (either by capnography or respiratory function monitoring) and cerebral oxygenation (near-infrared spectroscopy) is becoming more common within research settings. In this article, we will review the different modalities available for cardiorespiratory and neuromonitoring in the DR and assess the current evidence base on their feasibility, strengths, and limitations during preterm stabilization.

Transitional Changes in Cerebral Blood Volume at Birth

BACKGROUND

Near-infrared spectroscopy (NIRS) enables non-invasive measurements of changes in the concentration of oxygenated (x0394;HbO2) and reduced (x0394;HbR) haemoglobin. Changes in total haemoglobin (x0394;HbT = x0394;HbO2 + x0394;HbR) provide information on changes in cerebral blood volume (CBV).

OBJECTIVE

The aim was to evaluate the behaviour of CBV during immediate postnatal transition in term infants.

DESIGN

This observational study was conducted at the Medical University of Graz. NIRS measurements were carried out in term infants without need for respiratory support by using 'NIRO 200-NX' (Hamamatsu) over the first 15 min after birth.

RESULTS

109 infants with a mean gestational age of 38 + 6 weeks (±7 days) and birth weight of 3,242 g (±481) were included. Related to a reference value at minute 15, a significant decrease of HbT was observed for each minute within the study period. The mean (±SD) decrease of HbT of 17 (±40) µmol/l from minutes 2 to 15 represents a decrease of CBV of 1.0 ml/100 g brain (±2.2).

CONCLUSIONS

In healthy newborns, CBV decreased over the whole study period. This likely reflects a physiological process. The impact and clinical relevance of different CBV behaviour during immediate transition needs to be investigated in further studies.

Peripheral Muscle Near-Infrared Spectroscopy in Neonates: Ready for Clinical Use? A Systematic Qualitative Review of the Literature

BACKGROUND

Peripheral muscle near-infrared spectroscopy (NIRS) measurements are of increasing interest especially in the care of critically ill patients.

OBJECTIVE

The aim was to perform a systematic qualitative review on peripheral muscle NIRS measurements in the clinical care of term and preterm neonates.

METHODS

A systematic search of PubMed and Ovid Embase was performed using the following terms: neonate, neonates, newborn, newborns, infant, infants, near-infrared spectroscopy, NIRS, oxygenation, perfusion, oxygen extraction, peripheral, tissue, muscle, calf, forearm and thigh. Additional articles were identified by a manual search of the cited references. Only human studies were included.

RESULTS

Twenty-one studies were identified to use peripheral muscle NIRS measurements as a single method, 17 studies combined cerebral and peripheral muscle NIRS measurements and 1 study used multi-site NIRS measurements in human neonates. Two randomized studies were identified. Two additional publications were included because they provided important general information about peripheral muscle NIRS measurements.

CONCLUSION

In the care of critically ill neonates peripheral muscle NIRS measurements alone or in combination with cerebral or multi-site NIRS measurements provide useful additional information about peripheral circulation and oxygenation. This method is a promising tool in the recognition of early states of centralization (compensated shock) in this vulnerable group of patients. However, before this method can be used in the clinical routine it has to be tested as monitoring to guide interventions in further studies.

Time course study of blood pressure in term and preterm infants immediately after birth

Objective

To describe temporal changes in systolic, diastolic, and mean blood pressure (SBP, DBP, and MBP, respectively) in term and preterm infants immediately after birth.

Methods

Prospective observational two-center study. In term infants SBP, DBP, and MBP were assessed non-invasively every minute for the first 15 minutes, and in preterm infants every minute for the first 15 minutes, as well as at 20, 25, 30, 45, and 60 minutes after birth. Regression analyses were performed by gender and respiratory support in all neonates; and by mode of delivery, cord clamping time, and development of ultrasound-detected brain injury in preterm neonates.

Results

Term infants (n = 54) had a mean (SD) birth weight of 3298 (442) g and gestational age of 38 (1) weeks, and preterm infants (n = 94) weighed 1340 (672) g and were 30 (3) weeks gestation. Term infants’ SBP, DBP and MBP within the first 15 minutes after birth were independent of gender or respiratory support. Linear mixed regression analysis showed that preterm infants, who were female, born vaginally, had delayed cord clamping and did not require positive pressure ventilation nor develop periventricular injury or ventriculomegaly, had significantly higher SBP, DBP, and MBP at some measurement points within the first hour after birth.

Conclusions

We present novel reference ranges of BP immediately after birth in a cohort of term and preterm neonates. They may aid in optimization of cardiovascular support during early transition at all gestations.

Non-invasive measurements of ductus arteriosus flow directly after birth

OBJECTIVE

To assess ductus arteriosus (DA) blood flow directly after birth in healthy term infants after elective caesarean section.

DESIGN

In healthy term newborns, echocardiography was performed at 2, 5 and 10 min after birth to monitor cardiac output and DA blood flow. Heart rate (HR) was assessed using ECG.

SETTING

The delivery rooms of the Leiden University Medical Center.

PATIENTS

24 healthy term infants born after a caesarean section were included in this study.

RESULTS

Mean (SD) HR did not change (158 (18) beats per minute (bpm), 5 min (159 (23) bpm) and 10 min (156 (19) bpm). DA diameter decreased from 5.2 (1.3) mm at 2 min to 4.6 (1.3) mm at 5 min (p=0.01) to (3.9 (1.2) mm) (p=0.01) at 10 min. Right-to-left DA shunting was unaltered (median (IQR) 95 (64-154) mL/kg/min to 90 (56-168) mL/kg/min and 80 (64-120) mL/kg/min, respectively (ns)), whereas left-to-right shunting significantly increased between 2 and 5 min (41 (31-70) mL/kg/min vs 67 (37-102) mL/kg/min (p=0.01)) and increased significantly between 2 and 10 min (93 (67-125)) mL/kg/min (p<0.001). Right-to-left/left-to-right shunting ratio decreased significantly from 2.1 (1.4-3.1) at 2 min to 1.4 (1.0-1.8) at 5 min (p<0.0001) and to 0.9 (0.6-1.1) at 10 min (p<0.0001).

CONCLUSIONS

DA shunting changes swiftly from predominantly right-to-left shunting to predominantly left-to-right shunting at 10 min after birth, reflecting differential changes in pulmonary and systemic vascular resistance.

Platelet counts in the first seven days of life and patent ductus arteriosus in preterm very low-birth-weight infants

BACKGROUND

Decreased platelet number and/or function are related to patent ductus arteriosus (PDA) in mice. Whether this is also the case in human infants remains controversial.

OBJECTIVES

To investigate the association between platelet count nadir within the first 7 days of life and the rate of hemodynamically significant PDA (HSPDA), as well as the rate of response to the treatment with cyclooxygenase (COX) inhibitors.

METHODS

This is a retrospective study of a cohort of 194 very low-birth-weight (VLBW) infants (<1,500 g) with gestational age <30 weeks. HSPDA was assessed by echocardiography on day 3 of life.

RESULTS

HSPDA was present in 105 infants (54.1%). Of these, 101 were treated with COX inhibitors. The treatment failure rate was 21.8%. Median platelet count nadir and rate of thrombocytopenia - defined as platelet count <150 × 10(9)/l and graded as mild (100 to <150 × 10(9)/l), moderate (50 to <100 × 10(9)/l) or severe (<50 × 10(9)/l) - within the first 2 days of life were not significantly associated with the presence of HSPDA on day 3. Moreover, low platelet counts, either on days 1-2 or 3-7, were not significantly associated with the rate of response to treatment with COX inhibitors.

CONCLUSIONS

Our data provide further evidence for the lack of association between platelet counts within the first days of life and either spontaneous or pharmacological closure of the ductus arteriosus in VLBW infants.

Oxygen saturation trends in the first hour of life in healthy full-term neonates born at moderate altitude

Background: Transition from a parallel circulation in utero to an in-series circulation immediately after birth is partly an oxygen-dependent process. Relative hypoxemia with increasing altitude above sea level exerts a certain degree of stress on oxygen-dependent metabolic processes throughout the body.

Objective: The present study aimed to determine the reference values for oxygen saturation and the pre-ductal and post-ductal oxygen saturation trends during the first 60 min of life in healthy full-term neonates born at moderate altitude (1500-2500 m) using pulse oximetry.

Methods: This descriptive study was carried out over a period of three months started from July 2011 in the Neonatology Department of King Abdulaziz Specialist Hospital, Taif, Saudi Arabia. In this observational study, arterial oxygen saturation in the right hand and right foot of each infant was recorded by pulse oximetry immediately after birth and continuously within the first 60 min of life. The respiratory rate, heart rate, and blood pressure were measured at birth and at 1 h after birth. Cord blood gas and haemoglobin levels were also measured.

Results: The study was conducted in a hospital situated at an altitude of 1640 m above sea level. Immediately after birth, the mean pre-ductal SpO₂ in the right hand was 68% (51–80%); in the right foot, the mean post-ductal SpO₂ was 60% (40–77%). This difference was statistically significant (p < 0.01); however, it became statistically insignificant at 20 min (4–45 min) and disappeared at 25 min, when the SpO₂ in both limbs equalised at 88% (83–96%). SpO₂ levels > 94% were reached after 13 min (4–35) min pre-ductally and after 22 min (10–45 min) post-ductally. The mean respiratory rate, heart rate, and mean blood pressure at birth were 56/min, 140/min, and 34 mmHg, respectively; at 60 min, they were 40/min, 123/min, and 47 mmHg, respectively.

Conclusion: This study defined normal range of SpO₂ values in healthy full-term neonates born at moderate altitude in the first 60 minutes of life. These are expected to serve as base line data for normal neonates born at similar altitudes. With regard to pre-ductal and post-ductal oxygen saturation levels, cut-off values lower than those used at sea level should be adopted for neonates born at moderate altitudes.

Reference ranges for regional cerebral tissue oxygen saturation and fractional oxygen extraction in neonates during immediate transition after birth

OBJECTIVE

To define reference ranges for regional cerebral tissue oxygen saturation (crSO2) and regional cerebral fractional tissue oxygen extraction (cFTOE) during the first 15 minutes after birth in neonates requiring no medical support.

STUDY DESIGN

The crSO2 was measured using near infrared spectroscopy (Invos 5100 cerebral/somatic oximeter monitor; Somanetics Corp, Troy, Michigan) during the first 15 minutes after birth for term and preterm neonates. The near infrared spectroscopy sensor was placed on the left forehead. Peripheral oxygen saturation and heart rate were continuously measured by pulse oximetry, and cFTOE was calculated. Neonates were excluded if they required any medical support.

RESULTS

A total of 381 neonates were included: 82 term neonates after vaginal delivery, 272 term neonates after cesarean delivery, and 27 preterm neonates after cesarean delivery. In all neonates, median (10th-90th percentiles) crSO2 was 41% (23-64) at 2 minutes, 68% (45-85) at 5 minutes, 79% (65-90) at 10 minutes, and 77% (63-89) at 15 minutes of age. In all neonates, median (10th-90th percentiles) cFTOE was 33% (11-70) at 2 minutes, 21% (6-45) at 5 minutes, 15% (5-31) at 10 minutes, and 18% (7-34) at 15 minutes of age.

CONCLUSION

We report reference ranges of crSO2 and cFTOE in neonates requiring no medical support during transition immediately after birth. The use of cerebral oxygenation monitoring and use of these reference ranges in neonates during transition may help to guide oxygen delivery and avoid cerebral hypo-oxygenation and hyperoxygenation.