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

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.

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.

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.