Prevention of neonatal necrotizing enterocolitis

Enteral human IgG for prevention of necrotising enterocolitis: a placebo-controlled, randomised trial

BACKGROUND

Neonatal necrotising enterocolitis is a serious, commonly fatal disease in premature neonates. Although feeding with expressed breast milk and other good nursery practices are partly protective, preventive measures are needed. Treating neonates enterally with a mixture of human IgA and IgG, prepared from donated blood, has been claimed to protect against necrotising enterocolitis. However, no IgA preparation is available in Australia. Our aim, therefore, was to identify whether or not enteral IgG could prevent the disorder.

METHODS

We did a multicentre, double-blind, placebo- controlled trial. We randomly assigned 768 infants to receive human IgG 1200 mg/kg daily, and 761 to receive placebo, for up to 28 days. Treatment began at the same time as enteral feeding. The primary outcome measure was the proportion of infants who developed definite necrotising enterocolitis during the trial, and any deaths that resulted from the disorder in the treatment and placebo groups. Analysis was on an intention-to-treat basis.

FINDINGS

43 infants developed definite necrotising enterocolitis in the IgG group, ten of whom died. In the placebo group, 41 infants contracted the disorder and six died (p=0.47). 25 infants on IgG and 36 on placebo had suspect necrotising enterocolitis (p=0.14).

INTERPRETATION

Supplementation of enteral feeds with human IgG does not reduce necrotising enterocolitis.

Acidification of formula reduces bacterial translocation and gut colonization in a neonatal rabbit model

BACKGROUND/PURPOSE

The authors hypothesized that gastric acidity is protective because it is bactericidal. They tested acidified formula for protection against gut colonization and bacterial translocation.

METHODS

In vitro: Formula was acidified to pH of 2, 3, 4, 5 and innoculated with Enterobacter. Growth over time was quantitatively assessed. In vivo: 442 premature rabbit pups were sorted randomly and fed formula of pH 2, 3, 4, or 7, with ranitidine. Two models were utilized: (1) with bacterial challenge using a known acid sensitive organism, (2) without bacterial challenge to simulate natural gut colonization and to test against organisms of unknown acid sensitivity. Normal acid animals received pH 7 formula, no ranitidine. On day 3, the mesenteric lymph nodes (MLN), spleen, liver, and cecum were harvested and cultured.

RESULTS

Bacterial growth was inhibited at pH 2 and 3, growth was logarithmic above pH 4 (P<.001). Total and organ-specific translocation was reduced at pH 3 and below in both models (P<.05). Translocation with formula pH 3 equaled normal acid animals. Quantitative cecal colonization was reduced in pups receiving pH 3 and below in both models (P<.05).

CONCLUSION

Acidification of formula below pH 4 is bactericidal to enteric organisms. Acidified formula decreases bacterial translocation and gut colonization.

Duodenal microflora in very-low-birth-weight neonates and relation to necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency in the neonatal period. Small-bowel overgrowth with aerobic gram-negative bacteria has previously been implicated in the development of NEC. This prospective study performed quantitative bacteriology on 422 duodenal aspirates collected from 122 very-low-birth-weight (<1,500-g) newborns, at the time of routine changing of nasogastric tubes. Isolates of Enterobacteriaceae were typed by repetitive extragenic, palindromic PCR and pulsed-field gel electrophoresis. One or more samples from 50% of these infants yielded gram-negative bacteria, predominantly Escherichia coli, Klebsiella spp., and Enterobacter spp., with counts up to 10(8) CFU/g. The proportion of samples with gram-negative bacteria increased with postnatal age, while the percentage of sterile samples declined. Molecular typing revealed marked temporal clustering of indistinguishable strains. All infants had been fed prior to isolation of gram-negative organisms. Antibiotic use had no obvious effect on colonization with Enterobacteriaceae. There were 15 episodes of suspected NEC (stage I) and 8 confirmed cases of NEC (2 stage II and 6 stage III) during the study period. Duodenal aspirates were collected prior to clinical onset in 13 episodes of NEC. Seven of these yielded Enterobacteriaceae, of which five strains were also isolated from infants without NEC. Very-low-birth-weight infants have high levels of duodenal colonization with Enterobacteriaceae, with evidence of considerable cross-colonization with indistinguishable strains. There was no association between duodenal colonization with particular strains of Enterobacteriaceae and development of NEC.

Graft failure secondary to necrotizing enterocolitis in multi-visceral transplantation recipients: two case reports

We report on two recipients of multi-visceral grafts who exhibited sudden onset of acute abdomen discomfort 2 weeks post-transplantation after a fairly uneventful immediate post-operative course. Both patients were shown to have pneumatosis intestinalis and one had air in the portal vein. Both patients underwent exploration, which showed non-viable intestine (terminal ileum and colon in the first patient and the entire small intestine distal to the ligament of Treitz in the second patient). There was no vascular thrombosis. The necrotic intestine was resected in both cases. The first patient developed sepsis and died 15 days later despite the rescue efforts. The second patient was re-transplanted twice and is doing well. The histopathology of the segments involved revealed cryptitis, vasculitis, and features of transmural necrosis. Accordingly, both clinical and pathologic features are diagnostic of necrotizing enterocolitis. To our knowledge this is the first report of this complication following intestinal or multi-visceral transplantation.

Necrotizing enterocolitis: pathophysiology and prevention

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency in the neonatal intensive care unit. It is a disease of medical progress in that more very low-birth-weight neonates are surviving than ever before and are thus susceptible to this potentially devastating disease. NEC received very little attention in the literature before the 1970s but now is well known to all neonatologists and pediatric surgeons. The 1500 to 2000 infants that die every year from this disease in the United States and the large number of infants who develop short gut syndrome from this disease only represent the tip of the iceberg of the problems NEC causes. The widespread fear of NEC among neonatologists and pediatric surgeons has contributed in large part to the use of the IV route rather than the gastrointestinal tract for nourishing these infants for relatively long periods. The consequences of this include a high incidence of sepsis, high hospital costs, and potential long-term neurodevelopmental disability because of poor nutrition during a very vulnerable period of growth and development. The purpose of this review is to provide a brief overview of the clinical presentation and current treatment for NEC, then provide a discussion of the pathophysiology on which strategies for prevention can be formulated.

Lower incidence of necrotizing enterocolitis in infants fed a preterm formula with egg phospholipids

Necrotizing enterocolitis (NEC) causes approximately 4000 deaths/y and significant morbidity among U.S.-born preterm infants alone. Various combinations of inadequate tissue oxygenation, bacterial overgrowth, and enteral feeding with immaturity may cause the initial damage to intestinal mucosa that culminates in necrosis. Presently, there is not a way to predict the onset of the disease or to prevent its occurrence. As part of risk-benefit assessment, we compared disease in hospitalized preterm infants fed a commercial (control) preterm formula or an experimental formula with egg phospholipids for a randomized, double-masked, clinical study of diet and infant neurodevelopment. Infants fed the experimental formula developed significantly less stage II and III NEC compared with infants fed the control formula (2.9 versus 17.6%, p < 0.05), but had similar rates of bronchopulmonary dysplasia (23.4 versus 23.5%), septicemia (26 versus 31%), and retinopathy of prematurity (38 versus 40%). Compared with the control formula, the experimental formula provided 7-fold more esterified choline, arachidonic acid (AA, 0.4% of total fatty acids), and docosahexaenoic acid (0.13%). Phospholipids are constituents of mucosal membranes and intestinal surfactant, and their components, AA and choline, are substrates for intestinal vasodilatory and cytoprotective eicosanoids (AA) and the vasodilatory neurotransmitter, acetylcholine (choline), respectively. One or more of these components of egg phospholipids may have enhanced one or more immature intestinal functions to lower the incidence of NEC in this study. Regardless of the potential mechanism, a larger randomized trial designed to test the effect of this egg phospholipid-containing formula on NEC seems warranted.

Necrotizing enterocolitis: the search for a unifying pathogenic theory leading to prevention

During the past two decades, necrotizing enterocolitis has emerged as a major cause of mortality and morbidity in premature infants. The specific cause of the disease remains enigmatic, but several putative risk factors provide clues to a pathophysiology that seems to be multifactorial. With the use of newly developed scientific tools, an understanding of the basic pathophysiologic cascade that causes necrotizing enterocolitis is emerging, providing hope for improved treatment and prevention.

Epidemiology of necrotizing enterocolitis

The descriptive epidemiology of necrotizing enterocolitis (NEC) is presented. Areas addressed include incidence, race, sex, age of onset, mortality rates, and endemic versus epidemic disease. Both descriptive and case control studies are reviewed to uncover clues relevant to the causes, pathogenesis, and prevention of NEC.

Necrotizing enterocolitis. New thoughts about pathogenesis and potential treatments

Necrotizing enterocolitis (NEC) remains a major cause of morbidity and mortality in premature infants. An incomplete understanding of its pathogenesis has hampered efforts to devise an effective preventative strategy. New insights into the pathogenesis of NEC, particularly at the cellular and biochemical level, however, offer a rational basis for the development of new approaches to this disease.