Intestinal hemodynamics and oxygenation in the perinatal period

Clinical usefulness of splanchnic oxygenation in predicting necrotizing enterocolitis in extremely preterm infants: a cohort study

BACKGROUND

Impaired intestinal microcirculation seems to play an important role in the pathogenesis of necrotizing enterocolitis (NEC). A previous study showed that a SrSO2 < 30% is associated with an increased risk of developing of NEC. We aimed to determine the clinical usefulness of the cut off < 30% for SrSO2 in predicting NEC in extremely preterm neonates.

METHODS

This is a combined cohort observational study. We added a second cohort from another university hospital to the previous cohort of extremely preterm infants. SrSO2 was measured for 1-2 h at days 2-6 after birth. To determine clinical usefulness we assessed sensitivity, specificity, positive and negative predictive values for mean SrSO2 < 30. Odds ratio to develop NEC was assessed with generalized linear model analysis, adjusting for center.

RESULTS

We included 86 extremely preterm infants, median gestational age 26.3 weeks (range 23.0-27.9). Seventeen infants developed NEC. A mean SrSO2 < 30% was found in 70.5% of infants who developed NEC compared to 33.3% of those who did not (p = 0.01). Positive and negative predictive values were 0.33 CI (0.24-0.44) and 0.90 CI (0.83-0.96), respectively. The odds of developing NEC were 4.5 (95% CI 1.4-14.3) times higher in infants with SrSO2 < 30% compared to those with SrSO2 ≥ 30%.

CONCLUSIONS

A mean SrSO2 cut off ≥ 30% in extremely preterm infants between days 2-6 after birth may be useful in identifying infants who will not develop NEC.

Splanchnic oxygen saturation during reoxygenation with 21% or 100% O2 in newborn piglets

BACKGROUND

Increasing evidence recognizes the harm of excess oxygen to lungs, eyes, and brain of preterm infants, but not yet to the intestine. We assessed changes in splanchnic oxygenation during reoxygenation with 21% compared to 100% O₂ in a newborn piglet model of perinatal asphyxia.

METHODS

We randomized 25 piglets to control or intervention. Intervention groups underwent global hypoxia until acidosis and hypotension occurred. Piglets were reoxygenated for 30 min with 21% or 100% O₂ and observed for 9 h. We continuously measured regional splanchnic oxygen saturation (r_sSO₂) using near-infrared spectroscopy (NIRS). We calculated mean r_sSO₂ and r_sCoVar (as SD/mean). We measured PaO₂ and SaO₂, sampled from the right carotid artery.

RESULTS

Reoxygenation after global hypoxia restored r_sSO₂. Reoxygenation with 100% O₂ increased r_sSO₂ to values significantly higher than baseline. In intervention groups, r_sCoVar decreased during observation compared to baseline. We found a correlation between r_sSO₂ and PaO₂ (r = 0.420, P < 0.001) and between r_sSO₂ and SaO₂ (r = 0.648, P < 0.001) in pooled data from the entire experiment.

CONCLUSION

Reoxygenation after global hypoxia improves splanchnic oxygenation, but is associated with reduced variability of r_sSO₂. Reoxygenation with 100% O₂ exposes the intestine to hyperoxia. Splanchnic NIRS is able to detect intestinal hypoxia and hyperoxia.

IMPACT

Splanchnic oxygenation improves during reoxygenation after global hypoxia, though reoxygenation with 100% O₂ exposes the intestine to hyperoxia. Decreased variability of splanchnic oxygenation several hours after hypoxia and reoxygenation seems to be independent of the resuscitation strategy, and may indicate intestinal injury. Splanchnic NIRS monitoring was able to detect intestinal hypoxia and exposure to hyperoxia, as evidenced by a strong correlation between splanchnic oxygenation and arterial oxygen content.

Clinical Characteristics and Potential Pathogenesis of Cardiac Necrotizing Enterocolitis in Neonates with Congenital Heart Disease: A Narrative Review

Neonates with congenital heart disease (CHD) are at an increased risk of developing necrotizing enterocolitis (NEC), an acute inflammatory intestinal injury most commonly associated with preterm infants. The rarity of this complex disease, termed cardiac NEC, has resulted in a dearth of information on its pathophysiology. However, a higher incidence in term infants, effects on more distal regions of the intestine, and potentially a differential immune response may distinguish cardiac NEC as a distinct condition from the more common preterm, classical NEC. In this review, risk factors, differentiated from those of classical NEC, are discussed according to their potential contribution to the disease process, and a general pathogenesis is postulated for cardiac NEC. Additionally, biomarkers specific to cardiac NEC, clinical outcomes, and strategies for achieving enteral feeds are discussed. Working towards an understanding of the mechanisms underlying cardiac NEC may aid in future diagnosis of the condition and provide potential therapeutic targets.

Regional cerebral and splanchnic tissue oxygen saturation in preterm infants - Longitudinal normative measurements

BACKGROUND

To investigate regional splanchnic and cerebral tissue oxygen saturation in preterm infants <30 weeks gestation.

METHODS

Cerebral (cTOI) and splanchnic (sTOI) Tissue Oxygenation Index were measured weekly in 5 min epochs for a total period of 60 min using NIRS (NIRO-300) for the first 8 weeks of life, in 48 appropriately grown preterm infants born at <30 weeks gestation. Infants who developed HPI and/or NEC (n = 12) and those that died (n = 1) were excluded from our main outcome measure of regional gut and cerebral tissue oxygenation in healthy preterm infants <30 weeks gestation.

RESULTS

Median birthweight 789 g (460-1486), gestational age 25⁺⁶ weeks (23⁺⁰-29⁺¹) and 51.4% female. 217 NIRS measurements were completed across the first 8 weeks of life. Mean weekly cTOI ranged from 56.8-65.4% and sTOI ranged from 36.7-46.0%. Mean cTOI was significantly higher than mean sTOI (p < 0.001) throughout the first 8 weeks of life. Mean cTOI decreased significantly with increasing postnatal age [-0.59% each week (-1.26% to -0.07%) p = 0.04]. None of the examined confounding factors had a significant effect.

CONCLUSIONS

This is the first report of regional cerebral and splanchnic tissue oxygen saturation ranges during the first 8 weeks of life for preterm infants born at <30 weeks gestation.

Prediction of necrotizing enterocolitis in very low birth weight infants by superior mesenteric artery ultrasound of postnatal day 1: A nested prospective study

BACKGROUND

Necrotizing enterocolitis (NEC) is a devastating intestinal complication that occurs mainly in very-low-birth-weight infants (VLBWI). The study's aim was to investigate the possibility of early prediction of NEC on postnatal day 1 based on superior mesenteric artery (SMA) doppler ultrasonograpy.

METHODS

A prospective, observational, nested case control study (ChiCTR1900026197) was conducted to enroll VLBWIs (birth weight <1,500 grams) between October 2019 and September 2021. Doppler ultrasound measurement was done during the first 12 h of life and before first feeding. Infants developing NEC (stage II or III) subsequently were included in NEC group and infants spare of NEC were included in control group.

RESULTS

370 VLBWIs were enrolled (30 NEC cases). Among the ultrasound parameters, S/D was significantly higher in the NEC group (OR: 2.081, 95% CI: 1.411-3.069, P = 0.000). The area under the receiver operating curve (AUROC) following the Logistic regression was 0.704 (95% CI: 0.566-0.842, P = 0.001). The sensitivity of S/D for predicting NEC was 52.2% and the specificity was 92.7%. The critical value of S/D was 6.944 and Youden index was 0.449. Preplanned subgroup analysis confirmed that NEC infants of different stages were characterized by different SMA bloodstream. Small for gestational age (SGA) might be a confounding factor affecting intestinal bloodflow. And infants with delayed initiation or slow advancement of feeding exhibited characteristic intestinal perfusion.

CONCLUSIONS

In VLBWI, early SMA ultrasound shows the potential to predict NEC. It is reasonable to speculate that SMA bloodstream is related to intestinal structural and functional integrity.

Low Splanchnic Oxygenation and Risk for Necrotizing Enterocolitis in Extremely Preterm Newborns

OBJECTIVE

The aim of the study was to investigate whether splanchnic oxygenation (SrSO2), measured with near-infrared spectroscopy (NIRS), during the first week of life is associated with the risk of developing necrotizing enterocolitis (NEC) in extremely preterm infants.

METHODS

This was a prospective observational cohort study including extremely preterm infants (<28 weeks of gestation) born at Karolinska University Hospital from September 2014 to December 2016. Using 1-hour NIRS monitoring during enteral feeding, mainly continuous enteral feeding, in the first week of life we measured both cerebral and splanchnic oxygenation. Primary outcome was risk of developing NEC (Bell stage ≥ II). Secondary outcome was the association between low mean SrSO2 during the first week of life and postnatal age at full enteral nutrition.

RESULTS

We enrolled 52 extremely preterm newborns, but only 45 infants had complete NIRS data. One infant developed NEC within 1 day of NIRS monitoring and was excluded from the study. Median gestational age was 25.6 weeks (range 23.0-27.9) and median birth weight 698 g (range 485-1353). Eight infants developed NEC at the median postnatal age of 15 days (range 6-35). Median postnatal age at full enteral nutrition was 10 days (range 6-23). Infants with mean SrSO2 <30% had a higher risk for developing NEC compared with those with SrSO2 >30% (crude risk ratio 5.25; 95% CI [1.19-23.01]). Small for gestational age, gestational age, birth weight, postnatal age did not affect the results. We found no association between SrSO2 and age at full enteral nutrition.

CONCLUSIONS

Low mean SrSO2 (<30%) during the first week of life is associated with an increased risk for developing NEC in extremely preterm infants on mainly continuous enteral nutrition.

Maturation of Intestinal Oxygenation: A Review of Mechanisms and Clinical Implications for Preterm Neonates

Nutrient requirements of preterm neonates may be substantial, to support growth and maturation processes in the presence of challenging post-natal circumstances. This may be accompanied by substantial intestinal oxygen requirements. Preterm neonates may not be able to meet these oxygen requirements, due to a developmental delay in intestinal oxygenation regulation mechanisms. This review summarizes the available literature on post-natal maturation of intestinal oxygenation mechanisms and translates these changes into clinical observations and potential implications for preterm neonates. The different mechanisms that may be involved in regulation of intestinal oxygenation, regardless of post-natal age, are first discussed. The contribution of these mechanisms to intestinal oxygenation regulation is then evaluated in newborn and mature intestine. Finally, the course of clinical observations is used to translate these findings to potential implications for preterm neonates.

Measurement of gut oxygenation in the neonatal population using near-infrared spectroscopy: a clinical tool?

CONTEXT

Near-infrared spectroscopy (NIRS) is a non-invasive bedside monitor of tissue oxygenation that may be a useful clinical tool in monitoring of gut oxygenation in newborn infants.

OBJECTIVE

To systematically review literature to determine whether NIRS is a reliable tool to monitor gut oxygenation on neonatal units.

DATA SOURCES

PubMed and Embase databases were searched using the terms 'neonate', 'preterm infants', 'NIRS' and 'gut oxygenation' (2001-2018).

STUDY SELECTION

Studies were included if they met inclusion criteria (clinical trial, observational studies, neonatal population, articles in English and reviewing regional gut oxygen saturations) and exclusion criteria (not evaluating abdominal NIRS or regional oxygen saturations).

DATA EXTRACTION

Two authors independently searched PubMed and Embase using the predefined terms, appraised study quality and extracted from 30 studies the study design and outcome data.

LIMITATIONS

Potential for publication bias, majority of studies were prospective cohort studies and small sample sizes.

RESULTS

Thirty studies were reviewed assessing the validity of abdominal NIRS and potential application in neonates. Studies reviewed assessed abdominal NIRS in different settings including normal neonates, bolus and continuous feeding, during feed intolerance, necrotising enterocolitis and transfusion with packed red cells. Several observational studies demonstrated how NIRS could be used in clinical practice.

CONCLUSIONS

NIRS may prove to be a useful bedside tool on the neonatal unit, working alongside current clinical tools in the monitoring of newborn infants (preterm and term) and inform clinical management. We recommend further studies including randomised controlled trials looking at specific measurements and cut-offs for abdominal NIRS for use in further clinical practice.

Early cerebral and intestinal oxygenation in the risk assessment of necrotizing enterocolitis in preterm infants

BACKGROUND AND AIM

Predicting necrotizing enterocolitis (NEC) might help in preventing its devastating consequences. We aimed to investigate whether early cerebral and intestinal tissue oxygen saturation (rSO₂) and fractional tissue oxygen extraction (FTOE) predict the onset of NEC.

STUDY DESIGN

Prospective observational case-control study.

SUBJECTS

Infants with gestational age (GA) <32 weeks were included. For every NEC case we matched two controls based on GA, birth weight (BW), and a patent ductus arteriosus.

OUTCOME MEASURES

Cerebral oxygenation and intestinal oxygenation were prospectively monitored two-hours daily during the first five days after birth and once a week thereafter until five weeks after birth or until NEC developed. We used Kaplan-Meier analyses to determine the ability of near-infrared spectroscopy (NIRS) measurements, including their variability, to predict the development of NEC.

RESULTS

We included ten infants (median (range) GA 27.1 (24.6-29.4) weeks, BW 903 (560-1630) grams) who developed NEC at median postnatal day 13 (range: 4-43 days), and 20 matched controls. Infants with cerebral rSO₂ <70% within the first 48 h after birth developed NEC significantly more often than infants with cerebral rSO₂ ≥70% (odds ratio 9.00 (95% CI 1.33-61.14). Intestinal FTOE was higher in infants who developed NEC compared to controls during the last NIRS measurement at median 2 days (range: 1-7) before NEC onset (median 0.65 vs. 0.44).

CONCLUSIONS

Cerebral oxygenation monitoring early after birth might be valuable in the risk assessment of NEC development. Additionally, our results suggest that intestinal oxygenation is impaired before the onset of clinical NEC.

Splanchnic NIRS monitoring in neonatal care: rationale, current applications and future perspectives

Near infrared spectroscopy (NIRS) provides a non-invasive, continuous monitoring of regional tissue oxygenation. NIRS assessment of neonatal splanchnic oxygenation (SrSO₂) has gained increasing interest over the last decade, as local hypoxia and ischemia underlie the most feared gut complications in neonates. Current literature provides encouraging evidence in support of SrSO₂ reliability in detecting mesenteric hemodynamic changes related to various physiological and pathological conditions in-term and preterm infants. Even so, while splanchnic NIRS monitoring looks promising for investigating gut physiopathology in research settings, further studies are needed to evaluate its feasibility as a routine monitoring tool in neonatal care and to investigate its potential role in clinical decision making. After a brief introduction to NIRS technical principles, this review aims to provide a complete overview of current neonatal applications for splanchnic NIRS monitoring, to discuss its possible limitations and to suggest future directions for research and clinical applications.

Gastrointestinal Organoids: Understanding the Molecular Basis of the Host-Microbe Interface

In recent years, increasing attention has been devoted to the concept that microorganisms play an integral role in human physiology and pathophysiology. Despite this, the molecular basis of host-pathogen and host-symbiont interactions in the human intestine remains poorly understood owing to the limited availability of human tissue, and the biological complexity of host-microbe interactions. Over the past decade, technological advances have enabled long-term culture of organotypic intestinal tissue derived from human subjects and from human pluripotent stem cells, and these in vitro culture systems already have shown the potential to inform our understanding significantly of host-microbe interactions. Gastrointestinal organoids represent a substantial advance in structural and functional complexity over traditional in vitro cell culture models of the human gastrointestinal epithelium while retaining much of the genetic and molecular tractability that makes in vitro experimentation so appealing. The opportunity to model epithelial barrier dynamics, cellular differentiation, and proliferation more accurately in specific intestinal segments and in tissue containing a proportional representation of the diverse epithelial subtypes found in the native gut greatly enhances the translational potential of organotypic gastrointestinal culture systems. By using these tools, researchers have uncovered novel aspects of host-pathogen and host-symbiont interactions with the intestinal epithelium. Application of these tools promises to reveal new insights into the pathogenesis of infectious disease, inflammation, cancer, and the role of microorganisms in intestinal development. This review summarizes research on the use of gastrointestinal organoids as a model of the host-microbe interface.

An examination of the factors affecting intestinal wall integrity in newborns at birth

BACKGROUND

An understanding of the factors that influence intestinal wall integrity during the transition from fetal to neonatal life is important to elucidate and minimize potential contributions to the development of intestinal pathologies in vulnerable newborns.

OBJECTIVE

To assess the factors affecting intestinal wall integrity of late preterm and term newborns at birth.

METHODS

The concentrations of serum intestinal fatty acid-binding protein (I-FABP) as biomarker of intestinal wall injury, superoxide dismutase (SOD), and glutathione peroxidase (Gpx) as parameters of oxidative stress, and blood gas analyses were measured in the arterial cord blood of 80 newborns, delivered by spontaneous vaginal delivery (labor group) or elective cesarean delivery (non-labor group).

RESULTS

Compared with the non-labor group, I-FABP, SOD, and Gpx levels were significantly higher in the labor group. I-FABP concentration was inversely correlated with pH and BE and positively correlated with SOD and Gpx concentrations, second stage of labor duration, and active pushing time.

CONCLUSIONS

This study demonstrates that oxidative stress at birth and prolonged second stage of labor may lead to the intestinal injury, which is reflected in increased serum concentration of I-FABP.

The antecedents and correlates of necrotizing enterocolitis and spontaneous intestinal perforation among infants born before the 28th week of gestation

OBJECTIVE

To identify antecedents of "medical" necrotizing enterocolitis (mNEC), "surgical" NEC (sNEC), and spontaneous intestinal perforation (SIP) in newborns delivered before 28 weeks gestation.

STUDY DESIGN

Prospective multicenter cohort study. During study period, 2002- 2004, women delivering before 28 weeks gestation at one of 14 participating institutions were enrolled. Well defined antenatal and postnatal variables were collected. Bivariate analyses were performed to identify candidates for developing multinomial multivariable time-oriented logistic regression models.

RESULTS

Of the 1320 infants, 5% had mNEC, 6% had sNEC, and 4% had SIP. Antecedents of mNEC included mother's identification as Black, consumption of aspirin during the pregnancy, and vaginal bleeding after the 12th week of gestation. For sNEC the antecedents were maternal self- support, obesity and anemia during the pregnancy, birth before the 24th week, birth weight ≤750gm, and receipt of fresh frozen plasma (FFP) during the first postnatal week. An infant was at increased risk of SIP if the placenta had increased syncytial knots, birth occurred before the 24th week, and received FFP during the first week.

CONCLUSIONS

Maternal and neonatal characteristics might help identify at-risk ELGANs for NEC and SIP, who then may potentially benefit from targeted preventive strategies.

Relationship Between Near-Infrared Spectroscopy and Transabdominal Ultrasonography: Noninvasive Monitoring of Intestinal Function in Neonates

BACKGROUND

Near-infrared spectroscopy (NIRS) has the potential to continuously and noninvasively monitor intestinal function. This technology may be valuable because among neonates, intestinal maturity is highly variable and difficult to assess based solely on clinical signs. The aim of this study was to determine if there is an association between NIRS-based StO2 measurements and peristaltic activity assessed by transabdominal ultrasonography (US).

MATERIAL/METHODS

Nineteen neonates of gestational age >32 weeks were categorized according to "no/low" versus "normal/hyperactive" motility levels, based on blinded US scan results. StO2 was recorded every 2 s for 24 h, following the ultrasound recording. Differences between the resulting estimates of average StO2 (bias of fits) and goodness-of-fit (residuals) were evaluated.

RESULTS

Newborns with normal/hyperactive motility had higher mean StO2 than newborns with no/low motility (72.3±4.4 vs. 65.5±7.9, p<0.05, F=5.65). Residual errors were not significantly different between the 2 groups (p=0.213, F=0.213). A multivariate linear regression model using the means, residuals, and pairwise products of both, demonstrated more significant separation (0.47±0.26 vs. -0.24±0.33, p<0.01, F=27.4). A non-linear variant of the multivariate linear regression model demonstrated greatest separation (0.68±0.24 vs. -0.49±0.53, p<0.01, F=41.9).

CONCLUSIONS

This is the first study to demonstrate an association between NIRS-based StO2 measurements and peristaltic activity visualized by ultrasound imaging. NIRS may offer a continuous, noninvasive method to assess motility. This may have significant implications in premature infants at risk for feeding intolerance or necrotizing enterocolitis.

Effect of blood transfusion on intestinal blood flow and oxygenation in extremely preterm infants during first week of life

BACKGROUND

Extremely preterm infants receive frequent blood transfusions in the first week of life. The aim of this study was to measure the effect of blood transfusion on intestinal blood flow and oxygenation during the first week of life in extremely preterm infants.

STUDY DESIGN AND METHODS

Superior mesenteric artery (SMA) peak systolic velocity (PSV) and diastolic velocities were measured 30 to 60 minutes before and after transfusion. Splanchnic tissue hemoglobin index (sTHI), splanchnic tissue oxygenation index (sTOI), and splanchnic fractional tissue oxygen extraction (sFTOE) were measured continuously from 15 to 20 minutes before to after transfusion along with vital variables.

RESULTS

Twenty infants were studied (median gestational age, 26 weeks). Ten infants were partially fed (15-68 mL/kg/day). Heart rate and SaO2 remained unaltered; blood pressure increased significantly (p < 0.01) after transfusion. Mean SMA PSV (p = 0.63) and diastolic velocity (p = 0.65) remained unaltered. Mean pretransfusion SMA PSV was similar in partially fed (0.78 m/sec) compared to unfed infants (0.52 m/sec; p = 0.06) and the response to transfusion was not dissimilar. There was a significant increase in sTHI (mean difference, 32.3%; p < 0.01) and sTOI (14.6%; p = 0.03) and decrease in sFTOE (22.1%; p < 0.01) after transfusion. There was no significant difference in sTHI or sTOI between fed and unfed infants and their response to transfusion.

CONCLUSIONS

Blood transfusion increased blood pressure and intestinal tissue oxygenation but did not alter blood flow velocities. Partial feeding had no impact on intestinal blood flow and tissue oxygenation changes.