Postprandial gastrointestinal blood flow and oxygen consumption: effects of hypoxemia in neonatal piglets

Severe anemia predisposes very premature infants to transfusion-associated necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a catastrophic inflammatory bowel necrosis of premature infants. The etiology is unknown, but 25-40 % of cases have a history of red blood cell (RBC) transfusions in the preceding 48 h. This association has been noted in retrospective case/case-control studies, and many meta-analyses, and in a murine model. However, we still need human studies with larger, adequately powered cohorts to confirm this association and determine the operant mechanisms. The murine model shows that severe anemia leads to macrophage infiltration in the gut mucosa. Subsequent RBC transfusions containing free hemoglobin, activate nuclear factor-kappa B-mediated inflammatory changes and cause NEC-like mucosal injury. This review summarizes current human and experimental data to evaluate ta-NEC and hitherto unanswered mechanistic questions. If a causal relationship between transfusions and NEC is proven, these data could help develop effective therapeutic strategies.

A numerical study of the hemodynamic behavior and gas transport in cardiovascular systems with severe cardiac or cardiopulmonary failure supported by venoarterial extracorporeal membrane oxygenation

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) has been extensively demonstrated as an effective means of bridge-to-destination in the treatment of patients with severe ventricular failure or cardiopulmonary failure. However, appropriate selection of candidates and management of patients during Extracorporeal membrane oxygenation (ECMO) support remain challenging in clinical practice, due partly to insufficient understanding of the complex influences of extracorporeal membrane oxygenation support on the native cardiovascular system. In addition, questions remain as to how central and peripheral venoarterial extracorporeal membrane oxygenation modalities differ with respect to their hemodynamic impact and effectiveness of compensatory oxygen supply to end-organs. In this work, we developed a computational model to quantitatively address the hemodynamic interaction between the extracorporeal membrane oxygenation and cardiovascular systems and associated gas transport. Model-based numerical simulations were performed for cardiovascular systems with severe cardiac or cardiopulmonary failure and supported by central or peripheral venoarterial extracorporeal membrane oxygenation. Obtained results revealed that: 1) central and peripheral venoarterial extracorporeal membrane oxygenation modalities had a comparable capacity for elevating arterial blood pressure and delivering oxygenated blood to important organs/tissues, but induced differential changes of blood flow waveforms in some arteries; 2) increasing the rotation speed of extracorporeal membrane oxygenation pump (ω) could effectively improve arterial blood oxygenation, with the efficiency being especially high when ω was low and cardiopulmonary failure was severe; 3) blood oxygen indices (i.e., oxygen saturation and partial pressure) monitored at the right radial artery could be taken as surrogates for diagnosing potential hypoxemia in other arteries irrespective of the modality of extracorporeal membrane oxygenation; and 4) Left ventricular (LV) overloading could occur when ω was high, but the threshold of ω for inducing clinically significant left ventricular overloading depended strongly on the residual cardiac function. In summary, the study demonstrated the differential hemodynamic influences while comparable oxygen delivery performance of the central and peripheral venoarterial extracorporeal membrane oxygenation modalities in the management of patients with severe cardiac or cardiopulmonary failure and elucidated how the status of arterial blood oxygenation and severity of left ventricular overloading change in response to variations in ω. These model-based findings may serve as theoretical references for guiding the application of venoarterial extracorporeal membrane oxygenation or interpreting in vivo measurements in clinical practice.

Red blood cell transfusions post diagnosis of necrotizing enterocolitis and the deterioration of necrotizing enterocolitis in full-term and near-term infants: a propensity score adjustment retrospective cohort study

Background

Necrotizing enterocolitis (NEC) is one of serious gastrointestinal inflammatory diseases in newborn infants, with a high morbidity and mortality. Red blood cell transfusion (RBCT) plays a controversial and doubtful role in the treatment of NEC. In present study, we aim to analyze the association between RBCT and the deterioration of NEC.

Methods

This was a retrospective cohort study of near-term and full-term infants with a confirmed diagnosis of Bell’s stage II NEC between Jan 1, 2010 and Jan 31, 2020. The maternal and infant baseline characteristics, treatment information and laboratory test for each case were collected. The eligible subjects were divided into two groups based on receiving RBCT post NEC diagnosis or not. The propensity score was used to eliminate potential bias and baseline differences. A multivariate logistic regression model was used to adjust the propensity score and calculate the odds ratio (OR) and 95% confidential interval (CI) of RBCT for the deterioration of NEC.

Results

A total of 242 infants were included in this study, 60 infants had a history of RBCT post NEC diagnosis, and 40 infants deteriorated from Bell’s stage II to stage III. By adjusting the propensity score, RBCT post NEC diagnosis was associated with an increased risk for NEC deteriorating from stage II to III (adjusted OR 6.06, 95%CI 2.94–12.50, P = 0.000).

Conclusions

NEC infants who required RBCT post NEC diagnosis were more likely to deteriorate from stage II to III in full-term and near-term infants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03276-4.

Incomplete resection of necrotic bowel may increase mortality in infants with necrotizing enterocolitis

BACKGROUND

Infants with advanced necrotizing enterocolitis (NEC) often need surgical resection of necrotic bowel. We hypothesized that incomplete resection of NEC lesions, signified by the detection of necrotic patches in margins of resected bowel loops, results in inferior clinical outcomes.

METHODS

We reviewed the medical records of infants with surgical NEC in the past 15 years for demographic, clinical, and histopathological data. We also developed statistical models to predict mortality and hospital stay.

RESULTS

Ninety infants with surgical NEC had a mean (±standard error) gestational age of 27.3 ± 0.4 weeks, birth weight 1008 ± 48 g, NEC onset at 25.2 ± 2.4 days, and resected bowel length of 29.2 ± 3.2 cm. Seventeen (18.9%) infants who had complete resection of the necrosed bowel had fewer (4; 23.5%) deaths and shorter lengths of hospital stay. In contrast, a group of 73 infants with some necrosis within the margins of resected bowel had significantly more (34; 46.6%) deaths and longer hospital stay. The combination of clinical and histopathological data gave better regression models for mortality and hospital stay.

CONCLUSION

In surgical NEC, incomplete resection of necrotic bowel increased mortality and the duration of hospitalization. Regression models combining clinical and histopathological data were more accurate for mortality and the length of hospital stay.

IMPACT

In infants with surgical NEC, complete resection of necrotic bowel reduced mortality and hospital stay. Regression models combining clinical and histopathological information were superior at predicting mortality and hospital stay than simpler models focusing on either of these two sets of data alone. Prediction of mortality improved with the combination of antenatal steroids, chorioamnionitis, and duration of post-operative ileus, with severity of inflammation and hemorrhages in resected intestine. Length of hospital stay was shorter in infants with higher gestational ages, but longer in those with greater depth of necrosis or needing prolonged parenteral nutrition or supervised feedings.

Transfusion-related Gut Injury and Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) accounts for 10% of deaths in neonatal intensive care units. Several causal mechanisms are likely to lead to a final common disease phenotype. This article summarizes recent data on NEC following red blood cell (RBC) transfusion, with a focus on the most recent literature and ongoing trials. It highlights potential mechanisms from preclinical and human physiologic studies. It also discusses the role of feeding during RBC transfusion and the risk of NEC. Ongoing randomized trials will provide important data on how liberal or conservative approaches to RBC transfusion influence the risk of NEC.

Association of Bolus Feeding With Splanchnic and Cerebral Oxygen Utilization Efficiency Among Premature Infants With Anemia and After Blood Transfusion

IMPORTANCE

The pathogenesis of transfusion-associated necrotizing enterocolitis remains elusive. Splanchnic hypoperfusion associated with packed red blood cell transfusion (PRBCT) and feeding has been implicated, but studies of splanchnic tissue oxygenation with respect to feeding plus PRBCT are lacking.

OBJECTIVE

To investigate the oxygen utilization efficiency of preterm gut and brain challenged with bolus feeding during anemia and after transfusion using near-infrared spectroscopy.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study conducted from September 1, 2014, to November 30, 2016, at a tertiary neonatal intensive care unit included 25 hemodynamically stable infants with gestational age less than 32 weeks, birth weight less than 1500 g, and postmenstrual age younger than 37 weeks. Data analysis was performed from August 1, 2017, to October 31, 2018.

EXPOSURES

Infants received PRBCT (15 mL/kg for 4 hours) and at least 120 mL/kg daily of second hourly bolus feedings.

MAIN OUTCOMES AND MEASURES

Splanchnic fractional tissue oxygen extraction (FTOEs) and cerebral fractional tissue oxygen extraction (FTOEc) measures were made during 75-minute feeding cycles that comprised a 15-minute preprandial feeding phase (FP0) and 4 contiguous 15-minute postprandial feeding phases (FP1, FP2, FP3, and FP4; each 15 minutes long). The intraindividual comparisons of feeding-related changes were evaluated during the pretransfusion epoch (TE0: 4 hours before onset of transfusion) and 3 TEs after transfusion (TE1: first 8 hours after PRBCT completion; TE2: 9-16 hours after PRBCT completion; and TE3: 17-24 hours after PRBCT completion).

RESULTS

Of 25 enrolled infants (13 [52%] female; median birth weight, 949 g [interquartile range {IQR}, 780-1100 g]; median gestational age, 26.9 weeks [IQR, 25.9-28.6 weeks]; median enrollment weight, 1670 g [IQR, 1357-1937 g]; and median postmenstrual age, 34 weeks [IQR, 32.9-35 weeks]), 1 infant was excluded because of corrupted near-infrared spectroscopy data. No overall association was found between FTOEs and FPs in a multivariable repeated-measures model that accounted for transfusion epochs (primary analysis approach) (FP0: mean estimate, 11.64; 95% CI, 9.55-13.73; FP1: mean estimate, 12.02; 95% CI, 9.92-14.11; FP2: mean estimate, 12.77; 95% CI, 10.68-14.87; FP3: mean estimate, 12.54; 95% CI, 10.45-14.64; FP4: mean estimate, 12.98; 95% CI, 10.89-15.08; P = .16 for the FP association). However exploratory analyses of postprandial changes in FTOEs undertaken for each transfusion epoch separately found evidence of increased postprandial FTOEs during TE1 (mean [SD] FTOEs, 10.55 [5.5] at FP0 vs 13.21 [5.96] at FP4, P = .046). The primary and exploratory analyses found no association between FTOEc and feeding phases, suggesting that cerebral oxygenation may be protected.

CONCLUSIONS AND RELEVANCE

The findings suggest that enteral feeding may be associated with gut ischemia and potentially transfusion-associated necrotizing enterocolitis. The postprandial changes in FTOEs appear to warrant further investigation in larger randomized studies.

Impact of red blood cell transfusions on intestinal barrier function in preterm infants

OBJECTIVE

To determine the relationships of red blood cell (RBC) transfusion and enteral feeding to changes in intestinal permeability (IP) measured by the relative intestinal uptake of lactulose (La) and rhamnose (Rh) in preterm infants <33 wk gestation.

DESIGN/METHODS

Infants 240-326wk gestation received La/Rh solution enterally on study days 1, 8 and 15.Urinary La/Rh ratio was measured by HPLC. Hematocrit preceding transfusion, total RBC transfusion volume, volume/kg, and feeding status during each study interval (birth-d1; d1-d8, and d8-d15) were determined.

RESULTS

Of the seventeen (40.5%) subjects who received≥1 transfusion during the study period, 12 (70.6%) infants were <28 wk gestation and 5 (29.4%) infants were≥28 wk gestation, p < 0.0001. Lower pre-transfusion hematocrit was observed in intervals preceding high IP (La/Rh > 0.05) than in intervals preceding low IP (La/Rh≤0.05) measurements (33 vs 35.8, p = 0.1051). RBC transfusions occurred more frequently in intervals preceding high IP than in intervals preceding low IP (26.8%; vs 8.3%, p = 0.0275) with 5-fold higher total RBC volume and volume/kg in intervals preceding any time point with high IP. RBC transfusion during an interval was associated with a three-fold increased risk of high IP (aOR 2.7; 95% C.I 0.564-12.814; p = 0.2143). Exclusive breast milk exposure and post-menstrual age reduced the risk for high IP following RBC transfusion.

CONCLUSIONS

Both RBC transfusion number and volume was associated with subsequent high IP measurements in preterm infants <33 weeks gestation and potentially may contribute to impairment of the preterm intestinal barrier.

The WHEAT pilot trial-WithHolding Enteral feeds Around packed red cell Transfusion to prevent necrotising enterocolitis in preterm neonates: a multicentre, electronic patient record (EPR), randomised controlled point-of-care pilot trial

INTRODUCTION

Necrotising enterocolitis (NEC) is a potentially devastating neonatal disease. A temporal association between red cell transfusion and NEC is well described. Observational data suggest that withholding enteral feeds around red cell transfusions may reduce the risk of NEC but this has not been tested in randomised trials; current UK practice varies. Prevention of NEC is a research priority but no appropriately powered trials have addressed this question. The use of a simplified opt-out consent model and embedding trial processes within existing electronic patient record (EPR) systems provide opportunities to increase trial efficiency and recruitment.

METHODS AND ANALYSIS

We will undertake a randomised, controlled, multicentre, unblinded, pilot trial comparing two care pathways: continuing milk feeds (before, during and after red cell transfusions) and withholding milk feeds (for 4 hours before, during and for 4 hours after red cell transfusions), with infants randomly assigned with equal probability. We will use opt-out consent. A nested qualitative study will explore parent and health professional views. Infants will be eligible if born at <30+0 gestational weeks+days. Primary feasibility outcomes will be rate of recruitment, opt-out, retention, compliance, data completeness and data accuracy; clinical outcomes will include mortality and NEC. The trial will recruit in two neonatal networks in England for 9 months. Data collection will continue until all infants have reached 40+0 corrected gestational weeks or neonatal discharge. Participant identification and recruitment, randomisation and all trial data collection will be embedded within existing neonatal EPR systems (BadgerNet and BadgerEPR); outcome data will be extracted from routinely recorded data held in the National Neonatal Research Database.

ETHICS AND DISSEMINATION

This study holds Research Ethics Committee approval to use an opt-out approach to consent. Results will inform future EPR-embedded and data-enabled trials and will be disseminated through conferences, publications and parent-centred information.

TRIAL REGISTRATION NUMBER

ISRCTN registry ISRCTN62501859; Pre-results.

Epidemiology of Necrotizing Enterocolitis: New Considerations Regarding the Influence of Red Blood Cell Transfusions and Anemia

This article summarizes available evidence on the relationship between red blood cell transfusion and anemia, and necrotizing enterocolitis (NEC). We review recent studies that highlight the uncertainty of the effect of red blood cell transfusion on NEC and the potential role of anemia. We also discuss potential pathophysiologic effects of both red blood cell transfusion and anemia and highlight strategies to prevent anemia and red blood cell transfusion. We also discuss ongoing randomized trials that are likely to provide important new evidence to guide red blood cell transfusion practices.

Anemia, red blood cell transfusions, and necrotizing enterocolitis

In the past 15 years, multiple clinical studies have identified a temporal association between red blood cell (RBC) transfusions and necrotizing enterocolitis (NEC). With some variability, most of these studies indicate that up to one-third of all cases of NEC involving very low-birth weight infants may occur within 24-48h after receiving a RBC transfusion. There is also evidence that the risk of such transfusion-associated NEC may be higher in infants transfused with the greatest severity of anemia. In this article, we summarize the clinical evidence pertaining to these issues; specifically, the contribution of RBC transfusions, and the contribution of severity of underlying anemia, to the pathogenesis of a type of NEC potentially termed, "transfusion/anemia-associated NEC."

Preinjury Fed State Alters the Physiologic Response in a Porcine Model of Hemorrhagic Shock and Polytrauma

INTRODUCTION

Hemorrhagic shock and injury lead to dramatic changes in metabolic demands and continue to be a leading cause of death. We hypothesized that altering the preinjury metabolic state with a carbohydrate load prior to injury would affect subsequent metabolic responses to injury and lead to improved survival.

METHODS

Sixty-four pigs were randomized to fasted (F) or carbohydrate prefeeding (CPF) groups and fasted 12 h prior to experiment. The CPF pigs received an oral carbohydrate load 1 h prior to anesthesia. All pigs underwent a standardized injury/hemorrhagic shock protocol. Physiologic parameters and laboratory values were obtained at set time points.

RESULTS

Carbohydrate prefeeding did not convey a survival benefit; instead, CPF animals had greater mortality rates (47% vs. 28%; P = 0.153; log-rank [Mantel-Cox]). Carbohydrate prefeeding animals also had higher rates of acute lung injury (odds ratio, 4.23; 95% confidence interval, 1.1-16.3) and altered oxygen utilization. Prior to shock and throughout resuscitation, CPF animals had significantly higher serum glucose levels than did the F animals.

CONCLUSIONS

Carbohydrate prefeeding did not provide a survival benefit to swine subjected to hemorrhagic shock and polytrauma. Carbohydrate prefeeding led to significantly different metabolic profile than in fasted animals, and prefeeding led to a greater incidence of lung injury, increased multiorgan dysfunction, and altered oxygen utilization.

Red blood cell transfusions increase fecal calprotectin levels in premature infants

OBJECTIVE

We hypothesized that red blood cell (RBC) transfusions influence intestinal inflammation in very low birth weight (VLBW) infants. We also suspected that hematocrit (Hct) at transfusions and RBC storage time correlate with intestinal inflammation.

STUDY DESIGN

VLBW infants, without major congenital defects, intestinal perforation or necrotizing enterocolitis, were enrolled prospectively. Fecal calprotectin (FC) levels were measured from stool samples collected before and after RBC transfusions. Data on Hct and RBC storage time were collected.

RESULT

Data from 42 RBC transfusions given to 26 infants revealed that FC levels increased faster than baseline after RBC transfusions (P=0.018) and were higher in multiple-transfused infants (0 to 48 and >48 h post transfusion, P=0.007 and P=0.005, respectively). Lower Hct and RBC storage >21 days correlated with higher FC levels (P=0.044 and P=0.013, respectively).

CONCLUSION

RBC transfusions, anemia and prolonged RBC storage were associated with an increase in intestinal inflammation.

Immunologic and Hematological Abnormalities in Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a leading cause of mortality in preterm infants. This article reviews the immunologic and hematological abnormalities typically seen in infants with NEC, such as elevated plasma cytokine levels, thrombocytopenia, increased or decreased neutrophil counts, low monocyte counts, and anemia. Some of these findings may provide important diagnostic and prognostic information.

Necrotizing enterocolitis in infants with congenital heart disease: the role of red blood cell transfusions

Necrotizing enterocolitis (NEC) is a rare but catastrophic complication that may occur in newborns with congenital heart disease (CHD). In the preterm population, transfusion of red blood cells (RBCs) and use of RBCs with longer storage time have been independently associated with the development of NEC. To date, it is not known whether similar associations exist for the term newborn with CHD. This retrospective study identified the incidence of NEC among 1,551 newborns admitted to the authors' cardiac intensive care unit between 7 January 2002 and 7 January 2010. The study was limited to term newborns (>36 weeks gestation). To understand the impact of RBC transfusions on the development of NEC, a nested 2:1 matched case-control analysis was undertaken to compare RBC transfusion patterns between an age-matched group and a cardiac lesion-matched control group. In the study population, NEC developed in 45 term infants during the postoperative period. Of these 45 infants, 30 (66.7%) had single-ventricle heart defects, whereas 22 (48.8%) required surgery for aortic arch obstruction. The median patient age at NEC diagnosis was 21 days. The RBC transfusion rate was higher among the patients who experienced NEC (0.21/day) than among the control subjects (0.10/day) (p = 0.048). A multivariate analysis indicated that onset of NEC was associated with a greater number of RBC transfusions (odds ratio [OR] 1.83; 95% confidence interval [CI] 1.07-7.47; p = 0.045). The duration of RBC storage was not significantly longer in the NEC group (9 days) than in the control cohort (7 days) (p = 0.16). Increased exposure to RBC transfusions is associated with the development of NEC in term infants with CHD. Longer storage of RBCs does not appear to increase this risk. Although causality cannot be confirmed, these data prompt a careful review of RBC transfusion practices with this population.

Association between red cell transfusions and necrotizing enterocolitis

OBJECTIVE

Several case reports and retrospective studies have reported a temporal association between red blood cell (RBC) transfusions and necrotizing enterocolitis (NEC). In this article, we review the clinical evidence and biological plausibility of the association between RBC transfusions and NEC.

METHODS

A literature search was performed using the databases PubMed, EMBASE, and Scopus, and the electronic archive of abstracts presented at the annual meetings of the Pediatric Academic Societies.

RESULTS

Among all cases of NEC, 25 -40% patients were noted to have received an RBC transfusion within a 48 hour period prior to onset of NEC. Compared to infants who developed NEC unrelated to transfusion, neonates with transfusion-associated NEC were born at an earlier gestation, had lower birth weights, and had a delayed onset at 3-5 weeks of postnatal age.

CONCLUSIONS

Based on current clinical evidence, transfusion-associated NEC appears to be a plausible clinical entity. However, there is a need for cautious interpretation of data because all the studies that have been conducted until date are retrospective, and therefore, susceptible to bias. A large, prospective, multi-center trial is needed to evaluate the association between RBC transfusion and NEC.

Maternal preeclampsia is associated with increased risk of necrotizing enterocolitis in preterm infants

BACKGROUND

Necrotizing enterocolitis (NEC) is an important cause of mortality and morbidity in preterm infants.

AIMS

To evaluate the effect of maternal preeclampsia on the development and severity of NEC in premature infants.

STUDY DESIGN

Prospective observational study in a tertiary neonatal intensive care unit.

SUBJECTS

The preterm infants of ≤ 37 gestational age who were consecutively hospitalized were enrolled. The study group contained preterm infants born to a preeclamptic mother and the comparison group contained preterm infants born to a normotensive mother.

OUTCOME MEASURES

The primary outcome was to determine the association between preeclampsia and NEC.

RESULTS

A total of 88 infants had NEC diagnosis. The incidence of NEC in infants born to preeclamptic mothers (22.9%) was significantly higher compared with those born to normotensive mothers (14.6%). According to NEC stages, NEC was more advanced in preeclamptic mother infants. NEC developed significantly earlier in infants with NEC in the study group. The duration of NEC was also significantly longer in infants born to preeclamptic mothers. In multiple logistic regression model, preeclampsia was found to be predictive of NEC with an odds ratio of 1.74 (95% confidence interval 0.64-0.92).

CONCLUSIONS

Maternal preeclampsia may be an important risk factor for the development of NEC in premature infants as NEC incidence and severity of NEC were found to be significantly higher in premature infants born to preeclamptic mothers. The onset of NEC was significantly earlier and duration of NEC was longer in these infants.

Transfusion-related acute gut injury: feeding, flora, flow, and barrier defense

TRAGI (transfusion-related acute gut injury) is an acronym we proposed to characterize a severe neonatal gastrointestinal reaction temporally related to a transfusion of packed blood red cells (PRBCs) for anemia in very low birth weights. The following are in support of a causative relationship: (1) the timing of necrotizing enterocolitis after a PRBC transfusion not being random, (2) traditional risk factors for necrotizing enterocolitis are often absent, (3) significant anemia appears to be a universal finding, (4) the age of donor blood is often slightly older than controls, (5) TRAGI is not postnatal age dependent, and (6) TRAGI does not show a centering at 31 weeks' postconceptual age as does nontransfusion-related NEC. Although TRAGI is linked to the timing of PRBC transfusions, we propose a novel hypothesis that the convergence at 31 weeks' postconceptual age for classic NEC approximates the age of presentation of other oxygen delivery and neovascularization syndromes (eg, retinopathy of prematurity), suggesting its etiologic link to a generalized systemic maturational mechanism or another common developmental theme. This report will begin by reviewing the history of the clinical presentation and discovery of TRAGI and will then analyze various pathophysiologic mechanisms that may account for the phenomenon when clinicians render therapies. We will end by a call to action for randomized clinical trials to test various etiologic theories.

Intestinal hemodynamics and oxygenation in the perinatal period

The neonatal gastrointestinal tract is a site of intense anabolic and metabolic activity, as it is responsible for the assimilation of nutritional intake and exhibits accelerated growth shortly after birth. The hypermetabolic state of the gastrointestinal tract requires sufficient blood flow and oxygen delivery to sustain adequate oxygen consumption to meet these metabolic needs. Therefore, an understanding of the mechanisms regulating intestinal vascular perfusion in the normal state and during pathophysiological conditions in the perinatal period is important to elucidate potential contributions to the development of intestinal pathologies in the neonate. The goal of this review is to summarize the available literature on the regulation of intestinal blood flow and oxygenation in the fetus and newborn in normal states and during pathological stress.

Transfusion-associated necrotising enterocolitis in very low birth weight premature infants

OBJECTIVE

Our aim was to determine the relationship between red blood cell transfusion and necrotising enterocolitis (NEC) in all admitted very low birth weight (VLBW) infants with or without transfusion.

STUDY DESIGN

All VLBW neonates were categorised into five groups: (i) subjects that developed NEC <48 h after transfusion (n = 15); (ii) subjects that developed NEC >48 h after transfusion (n = 31); (iii) subjects that were never transfused but developed NEC, (n = 50); (iv) subjects that were transfused but did not develop NEC, (n = 250) and (v) subjects that were neither transfused nor developed NEC (n = 301).

RESULTS

A group of 647 infants were enrolled in the study. Mean gestational age and birth weight of the patients were 29 ± 3.1 weeks and 1157 ± 237 g, respectively. The mean age at the onset of NEC in the NEC groups were 20 ± 2.3 days, 12 ± 3 days and 11 ± 2.6 days, respectively (P < 0.05). The mean interval from the last transfusion to the onset of NEC was 16.8 ± 8.8 h in group 1 and 240 ± 50 h in group 2 (P < 0.05).

CONCLUSION

In this study, we sought to evaluate all VLBW infants, whether they received a transfusion or not. We suggest that transfusion associated NEC exists, but many other factors influence this multifactorial disease. The age of NEC onset was later in transfused vs non-transfused patients, whereas the interval between transfusion and NEC was shorter in transfused vs non-transfused patients.

Transfusion-related acute gut injury: necrotizing enterocolitis in very low birth weight neonates after packed red blood cell transfusion

OBJECTIVE

This is a repeat cohort study in which we sought to determine whether an association of necrotizing enterocolitis (NEC) <48 hours of a packed red blood cells (PRBC) transfusion was a prior sampling artifact.

STUDY DESIGN

All very low birth weight neonates with NEC Stage ≥ IIB admitted over an 18-month period were categorized for NEC: (1) <48 hours after a PRBC transfusion; (2) unrelated to the timing of PRBCs; and (3) never transfused.

RESULTS

Eight hundred eighty-three admissions over 18 months were reviewed; 256 were very low birth weight that resulted in 36 NEC cases and 25% were associated with PRBC (n = 9). PRBC-associated cases had lower birth weight, hematocrit, and rapid onset of signs (<5 hours). The timing of association of PRBC transfusion and NEC differed from random, showing a distribution that was not uniform over time (χ(2) = 170.7, df = 40; P < .000001) consistent with the possibility of a causative relationship in certain cases of NEC. Current weight at onset of NEC did not differ; however, the more immature the neonate the later the onset of NEC creating a curious centering of occurrence at a median of 31 weeks postconceptual age.

CONCLUSIONS

We conclude that PRBC-related NEC exists. Transfusion-related acute gut injury is an acronym we propose to characterize a severe neonatal gastrointestinal reaction proximal to a transfusion of PRBCs for anemia. The convergence at 31 weeks postconceptual age approximates the age of presentation of other O(2) delivery and neovascularization syndromes, suggesting a link to a generalized systemic maturational mechanism.

Doppler flow velocimetry in the superior mesenteric artery on the first day of life in preterm infants and the risk of neonatal necrotizing enterocolitis

OBJECTIVE

The purpose of this work was to relate Doppler indices of splanchnic perfusion and vascular resistance to the risk of developing necrotizing enterocolitis.

METHODS

We conducted a prospective cohort study with analysis of Doppler flow velocity waveforms of splanchnic vessels on the first day of life. Clinical management and diagnosis of necrotizing enterocolitis were performed blind to the Doppler results in a tertiary NICU on 64 eligible preterm neonates admitted for intensive care. We measured necrotizing enterocolitis using an objective diagnostic classification.

RESULTS

When adjusted for gestational age at birth, the following indices of the Doppler flow velocity wave form in the superior mesenteric artery were significantly predictive of the risk of necrotizing enterocolitis: end-diastolic velocity, mean velocity, and pulsatility index. The association between necrotizing enterocolitis and Doppler velocimetry indicative of high vascular resistance was independent of a range of other factors and comorbidities (race, mode of delivery, umbilical arterial catheter, growth restriction, patent ductus arteriosus, jaundice, respiratory distress syndrome, mechanical ventilation, and hypotension).

CONCLUSIONS

We concluded that neonates with high resistance patterns of blood flow velocity in the superior mesenteric artery on the first day of life are at increased risk of developing necrotizing enterocolitis.

Feeding growth restricted preterm infants with abnormal antenatal Doppler results

Absence or reversal of end diastolic flow (AREDF) in the umbilical artery is associated with poor outcome, and elective premature delivery is common. Feeding these infants is a challenge. They often have poor tolerance of enteral feeding, and necrotising enterocolitis may develop. This review explores current practice to see if there is evidence on which to base guidelines. The incidence of necrotising enterocolitis is increased in infants with fetal AREDF, especially when complicated by fetal growth restriction. Abnormalities of splanchnic blood flow persist postnatally, with some recovery during the first week of life, providing justification for a delayed and careful introduction of enteral feeding. Such a policy exposes babies to the risks of parenteral nutrition, with no trials to date showing any benefit of delayed enteral nutrition. Trials are required to determine the optimum timing for introduction of enteral feeds in growth restricted infants with fetal AREDF.

Early aggressive nutrition in preterm infants

Increasingly, neonatologists are realizing that current feeding practices for preterm infants are insufficient to produce reasonable rates of growth, and earlier and larger quantities of both parenteral and enteral feeding should be provided to these infants. Unfortunately, there is very little outcome data to recommend any particular nutritional strategy to achieve better growth. Instead, the rationale for feeding regimens in many nurseries has been quite variably extrapolated from animal data and human studies conducted in gestationally more mature and/or stable neonates. Additionally, there are no well-controlled, prospective studies that validate any nutritional regimen for the very preterm and or sick, unstable neonate. The goal of this review is to present available data to help define the risks and benefits of early parenteral and enteral nutrition, particularly in very preterm neonates, concluding with a more aggressive approach to feeding these infants than has been customary practice.

Reductions in cardiac output in hypoxic young pigs: systemic and regional perfusion and oxygen metabolism

We tested the hypotheses that, in hypoxic young pigs, reductions in cardiac output restrict systemic oxygen transport to a greater extent than does hypoxia alone and that compensatory responses to this restriction are more effective in higher than in lower priority vasculatures. To study this, 10- to 14-day-old instrumented awake hypoxic (arterial oxygen tension = 39 Torr) pigs were exposed to reduced venous return by inflation of a right atrial balloon-tipped catheter. Blood flow was measured with radionuclide-labeled microspheres, and oxygen metabolism was determined with arterial and venous oxygen contents from appropriate vessels. Hypoxia resulted in a reduction in oxygen tension; increases in cardiac output and perfusion to brain (72% over baseline), heart, adrenal glands, and liver without reductions to other organs except for the spleen; reductions in systemic and intestinal oxygen delivery; and increases in systemic and intestinal oxygen extraction without changes in systemic, cerebral, or intestinal oxygen uptake. During hypoxia, decreasing venous return was associated with increases in arterial lactic acid concentration and central venous pressure; attenuation of the hypoxia-related increase in cardiac output; sustained increases in brain (72% over baseline) and heart perfusion; reductions in lung (bronchial artery), pancreatic, renal, splenic, and intestinal (-50% below baseline) perfusion; decreases in systemic and gastrointestinal oxygen delivery; sustained increases in systemic and intestinal oxygen extraction; and decreases in intestinal oxygen uptake, without changes in cerebral oxygen metabolism. We conclude that when venous return to the heart is reduced in hypoxic young pigs, the hypoxia-related increase in cardiac output was attenuated and the relative reduction in cardiac output was associated with preserved cerebral oxygen uptake and compromised intestinal oxygen uptake. Regional responses to hypoxia combined with relative reductions in cardiac output differ from that of hypoxia alone, with the greatest effects on lower priority organs such as the gastrointestinal tract.

The effect of asphyxia on gut blood flow in term neonates

Transcutaneous Doppler ultrasound measurements were made of the superior mesenteric artery of 25 term infants to correlate the intestinal blood flow with neonatal acid-base status as measured in umbilical artery blood and newborn condition as reflected by Apgar score. Compared with the babies whose umbilical artery pH was higher than 7.20 (peak systolic velocity: 84.1 cn/sn, mean velocity 48.6 cm/sn), the blood flow of superior mesenteric artery was significantly decreased in the newborn babies whose umbilical artery pH was less than 7.20 (peak systolic velocity 48.8 cm/sn, mean velocity = 32.6 cm/sn). Although no such relationship existed between Apgar scores and superior mesenteric artery blood flow indices, a significant linear correlation between superior mesenteric artery blood flow and umbilical artery pH was noted. A reduction of intestinal circulation was observed during umbilical cord blood acidemia and hypoxemia.

Post-prandial effects in reactivity of forehead and mid-femoral skin blood flow and heart rate in neonates

The effect of post-prandial period on the cutaneous vascular reactivity was studied in twelve full-term infants on their 3rd postnatal day. The differences in vasomotor reactions between the forehead and femoral skin were also investigated. Two 10-min control registrations about 30 and 90 min after feeding were followed by a registration of equal duration during thermal stimulation of the skin. The lower extremity of each infant was stimulated by warm and cool air currents (5 cycles/min) to induce periodic vasomotor changes. The fast Fourier transform was used to compute variability spectra for the recorded skin blood flow, heart rate and respiratory wave form signals. The skin blood flow became synchronised to the thermal stimulation in both skin regions. Neither the spontaneous nor synchronised oscillations of the skin blood flow differed significantly between femoral skin and forehead. The post-prandial time did not have any influence on this synchronisation. Heart rate variability was synchronised to the periodicity of thermal stimulation more 1.5 h after feeding than 0.5 h after feeding. Respiration was not affected. The results show that increasing post-prandial time has no influence on the synchronised oscillations of skin blood flow. However, it potentiates reactivity of heart rate to perturbations in the peripheral vasculature.

Effects of intrauterine growth retardation on postnatal visceral and cerebral blood flow velocity

Blood flow velocity and pulsatility index were measured with Doppler ultrasound in the superior mesenteric artery, coeliac axis, and anterior cerebral artery in 18 very low birth weight, small for gestational age infants, and compared with findings from 18 weight matched, and 18 gestation matched, appropriate for gestational age controls. Mean velocity in the superior mesenteric artery was lower in the small for gestational age infants (15 cm/s) than in the gestation matched control group (20.4 cm/s). In those small for gestational age infants who had evidence of fetal hypoxia the mean velocity in the superior mesenteric artery was even lower (11.5 cm/s). There were no differences in velocity in the cerebral artery among the groups. Infants who were small for gestational age still had significantly lower superior mesenteric artery velocity than gestation matched controls at 1 week of age. The results suggest a specific reduction in visceral perfusion in infants who are small for gestational age and who have experienced fetal hypoxia, and this could predispose these infants to necrotising enterocolitis.

Mucosal injury induced by ischemia and reperfusion in the piglet intestine: influences of age and feeding

The pathogenesis of neonatal necrotizing enterocolitis is unknown, but enteral alimentation, infectious agents, and mesenteric ischemia have been frequently invoked as primary initiators of the disease. To define the vulnerability of the intestinal mucosa to ischemia and reperfusion in the developing piglet, we evaluated changes in mucosal permeability using plasma-to-lumen clearance of chromium 51-labeled ethylenediaminetetraacetic acid in the ileum of anesthetized 1-day-, 3-day-, 2-wk-, and 1-mo-old piglets as a function of (a) duration of intestinal ischemia (20, 40, or 60 min of total superior mesenteric artery occlusion), (b) feeding status (fasted or nursed), and (c) composition of luminal perfusate (balanced salt solution vs. predigested cow milk-based formula). Baseline chromium 51-labeled ethylenediaminetetraacetic acid clearance was not significantly altered by ischemia, irrespective of duration, or feeding in all age groups. However, clearances were significantly elevated during reperfusion after 1 h of total intestinal ischemia in all age groups, whether fasted or fed. Reperfusion-induced increases in clearance did not differ among age groups when the bowel lumen was perfused with a balanced salt solution. However, luminal perfusion with formula resulted in higher clearances in 1-day-old piglets compared with all older animals. Thus, the neonatal intestine appears to be more vulnerable to mucosal injury induced by ischemia and reperfusion in the presence of formula than the intestine of older animals.