Primary peritoneal drainage for increasing ventilatory requirements in critically ill neonates with necrotizing enterocolitis.

BACKGROUND/PURPOSE: Primary peritoneal drainage (PPD) is an established therapy for premature neonates with necrotizing enterocolitis (NEC) and free intraperitoneal air. This study seeks to evaluate the efficacy of PPD in ill premature neonates with severe abdominal distension and increasing ventilatory requirements without free intraperitoneal air. METHODS: Eleven neonates (gestational age, 27 +/- 0.59 weeks; age, 25 +/- 4.3 days; birth weight, 862 +/- 67 g) with NEC underwent bedside PPD under local anesthesia for rapid clinical deterioration characterized by severe abdominal distension and increasing ventilatory requirements. None showed radiographic evidence of free intraperitoneal air. Mean airway pressure (MAP) and oxygenation-index (OI) were analyzed 24 hours before, immediately before and 24 hours after surgery. The patients were followed up to discharge from hospital. Statistical analyses were performed using analysis of variance (ANOVA) for repeated measures. RESULTS: Mean airway pressure (MAP) showed a significant difference (P <.05) increasing from 7.1 +/- 0.75 cm H2O 24 hours before surgery to 11 +/- 1.3 cm H2O immediately before surgery and decreasing to 9.9 +/- 1.1 cm H2O 24 hours after drainage. Likewise, OI measured at the same time intervals showed significant differences (P <.05) deteriorating from 5 +/- 1.2 to 26 +/- 6.9 then improving to 13 +/- 3.5. A significant quadratic effect (P <.03) was evident for MAP and OI (ie, values significantly rose then fell). There were six 30-day survivors (55%), and 3 survived to discharge (27%). Of the long-term survivors, 2 required operative fistula closure, and 1 needed no further surgery. CONCLUSION: Bedside PPD for increasing ventilatory requirements and abdominal distension in critically ill neonates with nonperforated NEC is a simple technique that offers rapid stabilization, although ultimate mortality rate remains high.

Do critically ill surgical neonates have increased energy expenditure?

BACKGROUND/PURPOSE: Adult metabolic studies suggest that critically ill patients have increased energy expenditures and thus require higher caloric allotments. To assess whether this is true in surgical neonates the authors utilized a validated, gas leak-independent, nonradioactive, isotopic technique to measure the energy expenditures of a stable postoperative group and a severely stressed cohort. METHODS: Eight (3.46+/-1.0 kg), hemodynamically stable, total parenteral nutrition (TPN)-fed, nonventilated, surgical neonates (5 with gastroschisis, 2 with intestinal atresia, and 1 with intestinal volvulus) were studied on postoperative day 15.5+/-11.9. These were compared with 10 (BW = 3.20+/-0.2 kg), TPN-fed, extracorporeal life support (ECLS)-dependent neonates, studied on day of life 7.0+/- 2.8. Energy expenditure was obtained using a primed, 3-hour infusion of NaH(13)CO(3'), breath (13)CO(2) enrichment determination by isotope ratio mass spectroscopy, and the application of a standard regression equation. Interleukin (IL)-6 levels and C-reactive protein (CRP) concentrations were measured to assess metabolic stress. Comparisons between groups were made using 2 sample Student's t tests. RESULTS: The mean energy expenditure was 53+/-5.1 kcal/kg/d (range, 45.6 to 59.8 kcal/kg/d) for the stable cohort and 55+/-20 kcal/kg/d (range, 32 to 79 kcal/kg/d) for the ECLS group (not significant, P =.83). The IL-6 and CRP levels were significantly higher in the ECLS group (29 +/-11.5 v 0.7+/-0.6 pg/mL [P<.001], and 31+/-22 v 0.6+/-1.3 mg/L [P<.001], respectively). Mortality rate was 0% for the stable postoperative patients and 30% for the ECLS group. CONCLUSIONS: Severely stressed surgical neonates, compared with controls, generally do not show increased energy expenditures as assessed by isotopic dilution methods. These data suggest that the routine administration of excess calories may not be warranted in critically ill surgical neonates and support the hypothesis that neonates obligately redirect energy, normally used for growth, to fuel the stress response. This is a US government work. There are no restrictions on its use.

Long-term total parenteral nutrition-induced hepatobiliary dysfunction in a rabbit model.

BACKGROUND/PURPOSE: Currently, the reason for hepatobiliary dysfunction associated with long-term total parenteral nutrition (TPN) is much debated and still unclear. No agreement can be achieved about whether bacteriotoxins and sepsis, enteral starvation, consequences of abdominal operations, or the TPN solution itself is the real cause for the disease. Animal models were criticized for their short period of TPN and their failure to demonstrate cholestasis and bile duct proliferation. The aim of this study was to establish an animal model for long-term TPN in which the same alterations of the hepatobiliary system as observed in humans could be produced. METHODS: In this model, rabbits could be kept for the first time under continuous TPN for 4 weeks. Three serial liver biopsy sections were taken operatively from each animal and biochemical analyses were performed four times. A control group of enterally fed rabbits underwent exactly the same procedure in respect to operations and handling, so that differences in macroscopical, biochemical, and histological changes between both groups could be attributed exclusively to TPN. RESULTS: Only in the TPN group gallbladder distension developed in all animals after 1 week. After 3 and 4 weeks, viscous dark bile, sludge and stones, a slight rise in direct bilirubin, and a decline in plasma albumin and alkaline phosphatase was noted. In both groups liver biopsy results showed a similar degree of mild portal inflammation and single-cell necrosis at equivalent time points. These changes could be caused by antiseptics, antibiotics, anesthesia, and operations. Although mild to moderate proliferative changes and no hydropic degeneration developed in the control group during the same time, the TPN group generated marked proliferative and degenerative changes. We noted as early as 1 week after starting TPN a severe hydropic degeneration in 90% of the animals. Fibrosis and bile duct proliferation increased from a slight degree after 1 week up to a moderate to severe degree after 3 and 4 weeks, respectively. CONCLUSIONS: The hepatobiliary alterations associated with TPN in children, which cannot be separated clinically from consequences of multiple other factors, can almost identically be reproduced in our rabbit model as a clear consequence of TPN. Furthermore, the hydropic degeneration of the liver cells begins in zone 3 and is an early predominant feature of hepatobiliary dysfunction in rabbits and infants. It must be rated as a response to a direct cytotoxic effect on the liver cell.

The amniotic fluid as a source of cells for fetal tissue engineering.

PURPOSE: This study was aimed at determining whether fetal tissue constructs can be engineered from cells normally found in the amniotic fluid. METHODS: A subpopulation of morphologically distinct cells was isolated mechanically from the amniotic fluid of pregnant ewes (n = 5) and expanded selectively. Its lineage was determined by immunofluorescent staining against multiple intermediate filaments and surface antigens. Proliferation rates were determined by both oxidation and total DNA assays and compared with immunocytochemically identical adult and fetal sheep cells. Statistical analysis was by analysis of variance for repeated measures (ANOVA). After expansion, the amniocytes were seeded onto a polyglycolic acid polymer/poly-4-hydroxybutyrate scaffold. The resulting construct was analyzed by both optical and scanning electron microscopy. RESULTS: The immunocytochemical profile of expanded amniocytes was consistent with a mesenchymal, fibroblast/myofibroblast cell lineage. These cells proliferated significantly faster than comparable fetal and adult cells in culture. Amniocyte construct analysis showed dense, confluent layers of cells firmly attached to the scaffold, with no evidence of cell death. CONCLUSIONS: (1) Subpopulations of fetal mesenchymal cells can be isolated consistently from the amniotic fluid. (2) Mesenchymal amniocytes proliferate more rapidly in vitro than comparable fetal and adult cells. (3) Mesenchymal amniocytes attach firmly to polyglycolic acid polymer. The amniotic fluid can be a reliable and practical source of cells for the engineering of select fetal tissue constructs.

Long-term total parenteral nutrition and cholecystostomy tube in a rabbit model surgical procedure: management and preliminary results.

A rabbit model for long-term total parenteral nutrition (TPN), specially provided with cholecystostomy tube, was designed to investigate further aspects of TPN-associated cholestasis (TPN-AC). Modified surgical procedures concerning vascular access, cholecystostomy tube implantation and authors' original modalities for prolonged infusion management in the rabbit were used. Continuous TPN was performed in 30 young rabbits. Five animals died during the experiment (16.6%) and were excluded from final evaluation. Twenty-five rabbits were successfully maintained on continuous TPN for 28 days without restraint, having a cholecystostomy tube implanted 1 week after initiation of TPN. The collection of blood samples and daily parenteral administration of drugs were simply accomplished via a central venous catheter. At the same time the cholecystostomy tube enabled us to perform daily bile sampling. Saline irrigation of the biliary tree could be carried out in conscious animals maintained on TPN. A 4-week duration of TPN in this rabbit model made it possible for the first time to accomplish serial liver biopsies in order to verify the evolution of histologic changes in TPN-related hepatic dysfunction and possible effects of surgical and medical treatment. A preliminary analysis of operative findings and histology was carried out. An enlarged gallbladder containing hyperviscous bile was found in 80% of the animals 1 week after initiation of TPN. At this time it was possible to observe the first histologic changes consistent with TPN-associated hepatic disease, such as moderate to severe hepatocyte degeneration and portal inflammation. Biliary sludge was seen after 3 weeks of TPN in 70% of the rabbits, as well as a subsequent progression of TPN-associated histologic findings. Portal fibrosis and fatty liver degeneration occurred in 50% of the rabbits and bile duct proliferation in all animals. After 4 weeks of TPN (at autopsy) gallstones were found in 20% of TPN animals, as well as further progression of bile duct proliferation and fibrosis. Our first experiences with this model and preliminary results suggest that this concept offers new possibilities for further elucidation of TPN-associated hepatic dysfunction.

Parenteral nutrition-induced hepatobiliary dysfunction in infants and prepubertal rabbits.

We analyzed clinical, biochemical, and histo- logic parameters of ten infants with parenteral nutrition-induced hepatobiliary dysfunction. The data were compared with the results of a rabbit model. All infants were born prematurely with low birth weight. Their clinical diagnoses were necrotizing enterocolitis (6), gastroschisis (1), intrauterine volvulus (1), and lung hypoplasia (2). All required total (TPN) or partial parenteral nutrition for at least 8 weeks. All had repeated episodes of infections or sepsis. A rise in bilirubin and aminotransferase levels occurred after a minimum of 5 weeks; peak bilirubin levels ranged from 4 to 14 mg% and aminotransferases from 40 to 140 IU/l. One child later developed gallstones. Liver biopsies after 1 to 24 months showed fibrosis, bile-duct proliferation, cholestasis, and hydropic degeneration. All of the above-mentioned clinical factors have been accused of causing the observed biochemical and histologic changes. In our rabbit model we were able to produce almost identical symptoms by TPN alone: gallbladder distension, sludge, and stones developed after 1-4 weeks of TPN as well as uncharacteristic changes in aminotransferases and bilirubin after 4 weeks. Liver histology revealed severe hydropic degeneration of zone 3 as early as 1 week after beginning TPN. A rise of fibrosis and bile-duct proliferation after 1 to 4 weeks of infusion was statistically significant. Cholestasis, as was observed in the infants, could not be detected. In our model, all alterations observed could be attributed exclusively to TPN. We therefore assume that TPN was the true cause of the dysfunction. In a second experimental series infusions were reduced to 80% PN and free access to lab chow. These animals produced normal feces, indicating physiologic enteral stimulation. They developed the same degenerative and proliferative histologic changes, whereas gallbladder distension, sludge, and stones were not noted. We conclude that: (1) The TPN solution itself is responsible for the histologic changes in the liver, which is supported by the fact that hydropic degeneration of zone 3 is typical of a direct toxic effect; and (2) Complete enteral starvation with an absence of enteral stimulation causes disease of the lower biliary tract.