Enteral hypoxia/ischaemia and necrotizing enterocolitis

Placental abruption and the risk of necrotizing enterocolitis in neonates with birth weight ≥1500 grams; US national database study

BACKGROUND

The pathogenesis of necrotizing enterocolitis (NEC) is multifactorial, placental abruption is associated with serious neonatal complications attributed to disruption of the maternal-fetal vascular interface. This study aimed to investigate the association between placental abruption and NEC.

METHODS

We analyzed the United States (US) National Inpatient Sample (NIS) dataset for the years 2016-2018. Using the logistic regression model, the adjusted odds ratios (aOR) were calculated to assess the risk of NEC in infants born to mothers with placental abruption after controlling for significant confounders. Analyses were repeated after stratifying the population into two birth weight (BW) categories: <1500 g and ≥1500 g.

RESULTS

The study included 11,597,756 newborns. Placental abruption occurred in 0.16% of the population. NEC was diagnosed in 0.18% of infants, with a higher incidence (2.5%) in those born to mothers with placental abruption (aOR = 1.2, 95% CI: 1.1-1.3, p < 0.001). Placental abruption was associated with NEC only in infants with BW ≥ 1500 g (aOR = 1.34, 95% CI: 1.11-1.62, p 0.003).

CONCLUSION

Placental abruption is associated with an increased risk of NEC in neonates with BW ≥ 1500 g. Research is needed to explore the mechanisms behind this association and to develop targeted interventions to mitigate NEC risks in this population.

IMPACT

Placental abruption is associated with an increased risk of developing necrotizing enterocolitis (NEC) in neonates with a birth weight ≥1500 grams. This effect could be via direct in utero bowel injury or due to indirect postnatal compromise that occurs in these infants. This is the first study to specifically address the association between placental abruption and NEC in neonates ≥1500 g. The study used a national dataset that included all neonates delivered in the US, thereby allowing for the generalization of the findings after adjustment for multiple confounding factors. This study lays the groundwork for subsequent studies aimed at modifying feeding strategies and other neonatal management for the prevention of NEC in infants delivered after placental abruption.

Remote ischaemic conditioning in necrotising enterocolitis: a phase I feasibility and safety study

OBJECTIVE

Remote ischaemic conditioning (RIC) improves the outcome of experimental necrotising enterocolitis (NEC) by preserving intestinal microcirculation. The feasibility and safety of RIC in preterm infants with NEC are unknown. The study aimed to assess the feasibility and safety of RIC in preterm infants with suspected or confirmed NEC.

DESIGN

Phase I non-randomised pilot study conducted in three steps: step A to determine the safe duration of limb ischaemia (up to 4 min); step B to assess the safety of 4 repeated cycles of ischaemia-reperfusion at the maximum tolerated duration of ischaemia determined in step A; step C to assess the safety of applying 4 cycles of ischaemia-reperfusion on two consecutive days.

SETTING

Level III neonatal intensive care unit, The Hospital for Sick Children (Toronto, Canada).

PATIENTS

Fifteen preterm infants born between 22 and 33 weeks gestational age.

INTERVENTION

Four cycles of ischaemia (varying duration) applied to the limb via a manual sphygmomanometer, followed by reperfusion (4 min) and rest (5 min), repeated on two consecutive days.

OUTCOMES

The primary outcomes were (1) feasibility defined as RIC being performed as planned in the protocol, and (2) safety defined as perfusion returning to baseline within 4 min after cuff deflation.

RESULTS

Four cycles/day of limb ischaemia (4 min) followed by reperfusion (4 min) and a 5 min gap, repeated on two consecutive days was feasible and safe in all neonates with suspected or confirmed NEC.

CONCLUSIONS

This study is pivotal for designing a future randomised controlled trial to assess the efficacy of RIC in preterm infants with NEC.

TRIAL REGISTRATION NUMBER

NCT03860701.

Feed intolerance in preterm neonates with antenatal reverse end diastolic flow (REDF) in umbilical artery: a retrospective cohort study

Background: Feed intolerance is common in growth-restricted infants with antenatal AREDF (absent or reverse end-diastolic flow) and presumed to be more severe in those with reverse end diastolic flow (REDF). Natural history of feeding in REDF is rarely reported in the literature.Aims and objectives: To determine the incidence of feed intolerance and necrotizing enterocolitis (NEC) in neonates with antenatal REDF.Design: Preterm inborn neonates with gestation <37 weeks with antenatal REDF diagnosed between January 2015 and September 2017 were included in this retrospective cohort study. The primary outcome was the proportion of neonates having feed intolerance and NEC till discharge or death or transfer to other hospitals and time to achieve full enteral feeding (150 ml/kg/day).Results: Out of total 67 born with antenatal REDF, 8 were transferred out within 48 hours, 8 records not available and 4 excluded due to major malformations. The mean (SD) gestation and birth weight of the remaining 48 neonates were 32 (2) weeks and 1096 (291) g. The median (IQR) age of initiation of feeds was 30 (24-37) hours. Feeds were advanced by median (range) 20 (10-20) ml/kg/day in which 22 babies (45%) had at least 1 episode of feed intolerance at a median (IQR) age of 79 (40-120) hours requiring nil per oral for next 48 (18-96) hours. Full feeds were reached by median age (IQR) of nine (8-12) days. Only 3 neonates (6%) had NEC stage 2 or above as per Bell's staging.Conclusions: Feed intolerance is common in neonates with REDF though the risk of NEC is not high.What is known on this subject?Neonates with antenatal AREDF are at increased risk of feed intolerance and necrotizing enterocolitis.Early introduction of enteral feeds in neonates with AREDF with appropriate monitoring is safe without increased risk of necrotizing enterocolitis.AEDF which progresses to REDF is associated with increased morbidity.What does this study add?Early enteral feeding as early as 24 hours can be initiated in REDF if there are no abdominal symptoms and signs.Feed intolerance is high in REDF cases.The risk of NEC is not higher than what is seen in AEDF cases.

Necrotizing Enterocolitis in Moderate Preterm Infants

Necrotizing enterocolitis (NEC) is a devastating morbidity usually seen in preterm infants, with extremely preterm neonates (EPT ≤28 weeks) considered at highest risk. Moderately preterm infants (MPT 28-34 weeks) constitute a large percentage of NICU admissions. In our retrospective data analysis of NEC in a single regional perinatal center, NEC was observed in 10% of extremely EPT and 7% of MPT, but only 0.7% of late-preterm/term admissions. There was an inverse relationship between postnatal age at onset of NEC and gestational age at birth. Among MPT infants with NEC, maternal hypertensive disorders (29%) and small for gestational age (SGA-15%) were more common than in EPT infants (11.6 and 4.6%, resp.). Congenital gastrointestinal anomalies were common among late preterm/term infants with NEC. SGA MPT infants born to mothers with hypertensive disorders are particularly at risk and should be closely monitored for signs of NEC. Identifying risk factors specific to each gestational age may help clinicians to tailor interventions to prevent NEC.

Prematurity reduces citrulline-arginine-nitric oxide production and precedes the onset of necrotizing enterocolitis in piglets

Necrotizing enterocolitis (NEC) is associated with low plasma arginine and vascular dysfunction. It is not clear whether low intestinal citrulline production, the precursor for arginine synthesis, occurs before and thus predisposes to NEC or if it results from tissue damage. This study was designed to test the hypothesis that whole body rates of citrulline, arginine, and nitric oxide synthesis are low in premature pigs and that they precede NEC. Piglets delivered by cesarean section at 103 days [preterm (PT)], 110 days [near-term (NT)], or 114 days [full-term (FT)] of gestation were given total parenteral nutrition and after 2 days orogastrically fed infant formula for 42 h to induce NEC. Citrulline and arginine fluxes were determined before and during the feeding protocol. Gross macroscopic and histological NEC scores and plasma fatty acid binding protein (iFABP) concentration were determined as indicators of NEC. Intestinal gene expression for enzymes of the arginine pathway were quantitated. A lower ( P < 0.05) survival rate was observed for PT (8/27) than for NT (9/9) and FT pigs (11/11). PT pigs had higher macroscopic gross ( P < 0.05) and histological NEC ( P < 0.05) scores and iFABP concentration ( P < 0.05) than pigs of more advanced gestational age. PT pigs had lower citrulline production and arginine fluxes ( P < 0.05) throughout and a reduced gene expression in genes of the citrulline-arginine pathway. In summary, intestinal enzyme expression and whole body citrulline and arginine fluxes were reduced in PT pigs compared with animals of more advance gestational age and preceded the development of NEC. NEW & NOTEWORTHY Arginine supplementation prevents necrotizing enterocolitis (NEC), the most common gastrointestinal emergency of prematurity. Citrulline (precursor for arginine) production is reduced during NEC, and this is believed to be a consequence of intestinal damage. In a swine model of NEC, we show that intestinal gene expression of the enzymes for citrulline production and whole body citrulline and arginine fluxes are reduced and precede the onset of NEC in premature pigs. Reduced citrulline production during prematurity may be a predisposition to NEC.

Clinical predictors of necrotizing enterocolitis in premature infants

BACKGROUND

Necrotizing enterocolitis (NEC) has emerged as the most common neonatal gastrointestinal emergency, is the most common cause of death in neonates undergoing surgery, and accounts for yearly additional hospital charges in excess of $6.5 million. Prematurity is the only common variable identified in case-controlled studies exploring this disease.

OBJECTIVES

To improve the understanding of the relationship between factors related to intestinal inflammation and ischemia and the enteral feeding regimen in the context of the premature gut, thereby identifying antecedents of NEC.

METHODS

Data were collected from the medical records of 247 premature infants for this retrospective case-controlled study. Diagnosis of NEC, as defined by Bell Stages IIA-IIIB, was required for study group assignment (n = 84). Multivariate analysis techniques were used to predict the relationships between selected variables on the outcome of NEC.

RESULTS

Premature infants were 13 times more likely to develop NEC if the infant required increased respiratory support to maintain oxygenation during the early neonatal period and 6.4 times more likely to develop NEC if the infant did not receive nutritionally fortified enteral feedings of breast milk. When both factors were present, the odds of NEC increased 28.6 times when compared with infants without these factors.

DISCUSSION

The study findings extend knowledge of antecedents to NEC beyond prematurity, highlighting the role that respiratory support and nutritional fortification of enteral feedings play in the pathogenesis of this disease. Early identification of antecedents to NEC will improve critical care management of the neonate and, in turn, decrease the incidence of this devastating gastrointestinal disease. The study findings will guide further inquiry in neonatal nutrition, physiologic and metabolic functioning, and acute clinical management of the neonate.

Orchiectomy or testosterone receptor blockade reduces intestinal mucosal damage caused by ischemia-reperfusion insult

The aim of the present study was to investigate whether orchiectomy or administration of flutamide an antagonist of the testosterone receptor can reduce oxidative stress and histologic damage in the rat small bowel subjected to mesenteric ischemia/reperfusion (I/R) injury. A total of 32 Sprague-Dawley rats were divided into four groups. Group 1 was control (sham), group 2 was I/R, group 3 was I/R plus orchiectomy (orchiectomy was performed 14 days before I/R), group 4 was I/R plus flutamide (flutamide was given throughout 14 days before mesenteric IR). Rats were subjected to 45 min of mesenteric ischemia followed by 3 h of reperfusion. The levels of ileal malondialdehyde (MDA) and nitric oxide (NO) were found to be significantly lower in orchiectomy and flutamide treatment groups compared with I/R group (P < 0.05). The histopathological injury scores were consistent with the MDA and NO levels. These results suggest that castration or testosterone receptor blockade decreases the level of intestinal I/R injury in male rats and it is an another example for disease variations based on gender differences.

Role of nitric oxide in intestinal ischaemia-reperfusion injury studied using electron paramagnetic resonance

BACKGROUND

The role of nitric oxide in intestinal ischaemia-reperfusion (I/R) remains poorly defined, partly because of difficulty in detecting the nitric oxide free radical. In this study nitric oxide production was assessed during intestinal I/R by direct measurement using electron paramagnetic resonance (EPR), and the production of nitric oxide in jejunum and ileum was correlated with their different abilities to resist I/R injury.

METHODS

Rats were given an electron spin trapper (diethyldithiocarbamate/ferrous citrate) by intraperitoneal injection. Thirty-six segments each of jejunum and ileum were subjected to 15-90 min of ischaemia and 25 min of reperfusion. Tissue samples were analysed for EPR signals using a spectrometer.

RESULTS

Mean(s.d.) basal nitric oxide level was significantly higher in ileum (3.39(1.42) units) than jejunum (0. 65(0.05) units) (P = 0.0005). Increasing ischaemic times in the ileum resulted in decreasing nitric oxide levels (85, 32 and 13 per cent of basal level at 30, 60 and 90 min respectively); reperfusion resulted in further nitric oxide reduction (mean decrease 26 per cent). Severe (grade 3) histological damage was observed in low nitric oxide states (after 15 min of I/R in jejunum, 60 min of I/R in ileum).

CONCLUSION

Nitric oxide can be measured in intestinal tissues directly by EPR. The findings support a protective role for nitric oxide in I/R, and offer an explanation for the greater resistance to I/R of ileum.