The effect of endotoxin on intestinal mucosal permeability to bacteria in vitro.

OBJECTIVE: To examine the role of the intestinal mucosa in bacterial translocation, in vitro bacterial passage across ileal mucosal segments mounted in Ussing chambers were studied in control and endotoxin (lipopolysaccharide)-treated rats. DESIGN: Experimental study. MATERIALS AND METHODS: Three groups of rats were studied. The experimental group received an intraperitoneal injection of lipopolysaccharide, while controls received an equivalent volume of saline solution; a third group received no treatment. Twenty-four hours later, all groups underwent laparotomy and organ culture to assess bacterial translocation. At the same time, a segment of mucosa from the terminal ileum of each animal was mounted in a Ussing chamber, and the transmucosal passage of labeled Escherichia coli from the luminal to serosal surface was assessed by results of serial cultures. RESULTS: In vivo bacterial translocation occurred in 100% of the lipopolysaccharide-treated animals, significantly higher than the incidence seen in controls (25%; P < .05). In vitro passage of labeled E coli across ileal mucosa in the Ussing chamber occurred in 78% of lipopolysaccharide-treated animals, while in controls transmucosal passage was seen in only 14% (P < .05). Histologic examination of mucosa from both groups using light and transmission electron microscopy demonstrated no structural differences between groups. CONCLUSIONS: Increased permeability to bacteria at the mucosal level contributes to the bacterial translocation seen in endotoxemia.

Effect of secretory IgA on transepithelial passage of bacteria across the intact ileum in vitro.

BACKGROUND: Bacterial translocation is a process believed to result in nosocomial infections. Secretory IgA (sIgA) may have a role in the prevention of translocation by its ability to bind and aggregate bacteria, a function termed "immune exclusion." The present study was done to determine the effect of specific binding of sIgA to bacteria on the movement of these organisms across the intact epithelial membrane. STUDY DESIGN: Bacterial translocation across intact intestinal segments of rats were assessed in vitro using the Ussing model. Secretory IgA (0.25 mg per mL) from pooled human colostrum was added to the perfused segments of ileum in the Ussing system. Subsequently, the membranes were exposed to 5 x 10(9) cfu per mL Escherichia coli on their mucosal side. A second experiment tested the effect of human IgG when perfused with E. coli using the same preparation. All experiments had paired matched rats in a control group without immunoglobulin. The ability of sIgA and IgG to bind to E. coli was studied by an in vitro assay, as well as by transmission electron microscopy and immunofluorescence of random IgA/E. coli experiments. Measurements obtained in all experimental and control groups were the incidence and amount of bacterial passage and the potential difference generated by the intestinal segments (an index of viability). RESULTS: There were no differences in potential difference between control and experimental groups in either of the two experiments. Secretory IgA bound E. coli and completely prevented passage of E. coli as compared with rats in the control group. IgG bound E. coli; however, the incidence of passage was equal to that of rats in the control group. However, the presence of IgG resulted in a significantly reduced number of bacteria that passed when compared with controls (p < 0.05). Electron microscopic studies revealed intact surface morphology and immunofluorescence revealed aggregates of IgA and E. coli on the mucosal, but not submucosal, surface of the ileal membranes. CONCLUSIONS: This study provides direct evidence of immune exclusion by sIgA. When bound to bacteria, it prevents passage across a morphologically intact segment of viable intestinal tissue.

Inhaled nitric oxide in congenital diaphragmatic hernia.

Pulmonary hypertension is a major complication of congenital diaphragmatic hernia (CDH). Inhaled nitric oxide (NO) is a selective pulmonary vasodilator because it produces vasodilatation of the pulmonary vasculature without systemic hypotension. In experimental and clinical studies, inhaled NO ameliorates pulmonary hypertension and improves gas exchange. The goal of the present study was to determine the extent to which infants with CDH respond to inhaled NO. Four newborn infants with CDH complicated by severe respiratory insufficiency and right-to-left shunting received inhaled NO. In three patients, postductal oxygenation improved in response to small concentrations of NO (5 to 10 ppm); two received NO after operative repair, and the third both before and after repair. However, tachyphylaxis developed in all cases within 1 to 6 days. A fourth patient received inhaled NO in an attempt at weaning from ECMO. He did not respond, remaining hypoxic despite 80 ppm NO, and continued to require ECMO. In the three patients who responded to inhaled NO, plasma nitrites and nitrates (stable oxidative end products of NO) accumulated over time, but not in the patient who did not respond. The accumulation of nitrite and nitrate in plasma may reflect alveolar-capillary NO absorption, and may identify patients who will respond to continued inhaled NO. Methemoglobin remained below 1.9% in all four babies. Selected infants with CDH may respond to NO, but the benefit may be temporary.

Renal artery occlusion in pediatric blunt abdominal trauma--decreasing the delay from injury to treatment.

The cases of seven children treated from 1980 through 1991 with blunt renal artery injuries were reviewed to determine (1) if computed tomography alone could eliminate the need for intravenous pyelography (IVP) or arteriography (ART); and (2) the causes of management delays. The diagnosis of arterial occlusion was suggested by the lack of renal contrast enhancement in six patients with CT scans and in two patients with IVP. In three patients ART was merely confirmatory. The diagnosis was suggested by IVP or CT scan within a mean of 4.7 hours of injury, but ART added an additional mean 2.3 hours to the diagnostic workup. There was an additional 3.9-hour average delay in the operating room before revascularization. Six patients underwent revascularization. Four had minimal function by postoperative renal scans. Renal artery occlusion is rapidly detected by contrast-enhanced CT scanning without IVP or ART. The time period from diagnosis to revascularization must be expedited to improve renal outcome.

Catheter sepsis in short-bowel syndrome.

Catheter sepsis with catheter removal is an important problem in patients with short-bowel syndrome. We determined the incidence of catheter sepsis and the catheter salvage rate in 20 pediatric patients with short-bowel syndrome. To evaluate the intestine as a source and translocation as the pathophysiologic mechanism for catheter sepsis, we identified the sepsis organisms, compared them with the fecal flora, and used mesenteric lymph node cultures to document translocation. The incidence of catheter sepsis was significantly higher in patients with short-bowel syndrome than in patients without short-bowel syndrome (7.8 vs 1.3 per 1000 catheter days). Overall catheter salvage was 42% and was highest in gram-negative sepsis (71%). Enteric organisms were responsible for 62% of cases of catheter sepsis in patients with short-bowel syndrome vs 12% in patients without short-bowel syndrome. Anaerobes were strikingly absent in 25 of 28 stool cultures. The sepsis organism was identified in the fecal flora in 19 of 28 cases. The dominant fecal organism or yeast was the septic organism in 12 of these 19 cases and was isolated in three of four mesenteric lymph node cultures. Our findings support translocation as a mechanism in catheter sepsis in patients with short-bowel syndrome.

The effect of E coli virulence on bacterial translocation and systemic sepsis in the neonatal rabbit model.

In the surgical neonate, three factors that promote bacterial translocation and systemic infection are: (1) intestinal bacterial colonization and overgrowth; (2) compromised host defenses; and (3) disruption of the mucosal epithelial barrier. The newborn rabbit provides an excellent model to study these factors. Like the human, there is early closure of the gut mucosa to macromolecules, and nutrition can be maintained by breast or formula feeding. This study examines translocation and systemic sepsis after colonization with virulent K1 and avirulent K100 strains of Escherichia coli. New Zealand white rabbit pups (2 to 5 days old) were studied. The gastrointestinal tracts of 12 were colonized with K1 E coli; 14 were colonized with K100 E coli; 12 control animals were not inoculated. Mesenteric lymph node (MLN), liver, spleen, and colon homogenate were cultured 72 hours postinoculation. No bacteria were isolated from the colons of all but one control animal. Translocation or systemic sepsis did not occur. Translocation to the MLN was significantly increased (P less than .03) in K1 (50%) and K100 (36%) groups compared with controls (0%). Translocation to liver and spleen (systemic sepsis) was significantly increased (P less than .03) in K1 animals (67%) compared with K100 (0%) or controls (0%). Colonization by both strains of E coli led to translocation to the MLN, but only K1 E coli caused systemic sepsis. This suggests that although colonization by E coli in the newborn leads to translocation to the MLN, progression to systemic sepsis is the result of characteristics of the bacteria and/or neonatal host responses.

Characterization of neonatal multisystem organ failure in the surgical newborn.

With advances in critical care, multisystem organ failure (MSOF) has replaced single organ failure as the major cause of death in adult patients. The purpose of this report is to characterize neonatal MSOF (NMSOF) in the surgical newborn. The records of 84 infants who died during a 5-year period in the surgical neonatal intensive care unit were reviewed. There was sufficient information available in 10 newborns to characterize the NMSOF syndrome. Criteria for renal, hepatic, microvascular, pulmonary, cardiac, and hematologic failure were developed. The sequence of organ failure was determined by calculating the number of days prior to death when these criteria were first noted. Systemic infections were recorded. The sequence of organ failure was as follows: microvascular (edema) 17 +/- 10 days, renal 14 +/- 7 days, hepatic 13 +/- 5 days, hematologic 8 +/- 4 days, pulmonary 5 +/- 2 days, and cardiac 3 +/- 2 days. Adult respiratory distress syndrome (ARDS) was absent. The 10 infants showed both culture-positive sepsis (8) and culture-negative sepsis (2). This is the first report to characterize NMSOF in newborn surgical patients. The earliest findings were edema, followed by renal and hepatic failure. In contrast to adult MSOF, anasarca is a prominent early finding, pulmonary failure develops late, and classic ARDS is absent.

The hidden mortality in surgically treated necrotizing enterocolitis: fungal sepsis.

From 1979 to 1986, 82 infants underwent surgical treatment for necrotizing enterocolitis (NEC), with 36 deaths. The records of 30 of the 36 infants who died were available for review. Fungal colonization and sepsis, the sites of infection, and timing of diagnosis and therapy were determined. Sixteen of 30 (53%) neonates had no evidence of fungus. Six (20%) were colonized with Candida species. Eight (27%) had fungal sepsis, with two of these eight found only at necropsy. Positive fungal blood cultures were a late finding. In only four of the six patients with positive blood cultures were the results known in time to initiate treatment with amphotericin B. Two of these four babies received less than 2 days of amphotericin B treatment prior to death. Fungal sepsis is a significant lethal factor in the surgical mortality of NEC. Vigorous efforts at earlier diagnosis are mandatory.

Failure of tumor necrosis factor to produce hypotensive shock in the absence of endotoxin.

Tumor necrosis factor (TNF) is reported to cause a shock syndrome similar to that produced by endotoxin (LPS). The purpose of this study was to determine the relationship between TNF and LPS in causing shock. Eighty rats received infusions of either TNF, LPS, or TNF plus LPS, as compared with saline solution. Temperature, blood, and tissue specimens were obtained at 2 hours. Blood pressure was measured over 4 hours in a separate group of awake rats. Mortality was assessed over 24 hours. Neither TNF (1 mg/kg) nor LPS (1 mg/kg) altered hematocrit, blood gases, temperature, or caused hypotension or mortality. If the same dose of TNF was combined with LPS, however, there was significant (p less than 0.05) hemoconcentration and metabolic acidosis associated with hypotension and 100% mortality by 4 hours. Pathologic changes were restricted to the small intestine and occurred in this group only. It was concluded that TNF does not cause hypotension or shock in the rat. TNF will cause lethal shock, however, if combined with a sublethal dose of endotoxin. This suggests that synergy between TNF and endotoxin is important in septic shock.

Transplantation of multiple abdominal viscera.

Two children with the short-gut syndrome and secondary liver failure were treated with evisceration and transplantation en bloc of the stomach, small intestine, colon, pancreas, and liver. The first patient died perioperatively, but the second lived for more than 6 months before dying of an Epstein-Barr virus-associated lymphoproliferative disorder that caused biliary obstruction and lethal sepsis. There was never evidence of graft rejection or of graft-vs-host disease in the long-surviving child. The constituent organs of the homograft functioned and maintained their morphological integrity throughout the 193 days of survival.

Breath hydrogen excretion as a screening test for the early diagnosis of necrotizing enterocolitis.

We measured breath H2 excretion in 122 neonates from birth to 1 month of age. The patients weighed less than 2000 g at birth and thus were at risk for developing necrotizing enterocolitis (NEC). Hydrogen excretion was normalized for the quality of the expired air by dividing by the carbon dioxide pressure of the gas sample. The mean (+/- SD) peak H2/CO2 ratio was significantly different between the seven patients who subsequently developed NEC (9.4 +/- 2.7 ppm/mm Hg) and the 115 patients who did not (5.0 +/- 3.5 ppm/mm Hg). The prevalence of NEC was 5.7% in the present study. Defining a positive test as one with a ratio value of greater than or equal to 8.0 ppm/mm Hg, the resulting screening test had a sensitivity of 86% and a specificity of 90%. The screening test yielded a 33% predictive value of a positive test and a 99% predictive value of a negative test. High H2 excretion occurred eight to 28 hours before the earliest clinical signs of NEC. Breath H2 excretion is a simple noninvasive test that may be useful in the management of the premature neonate at risk for the development of NEC.

Inappropriate fluid response in congenital diaphragmatic hernia: first report of a frequent occurrence.

Safe management of the newborn infant with congenital diaphragmatic hernia (CDH) requires precise fluid administration to avoid hypovolemia or fluid overload. Twenty-two CDH patients and 12 infants who underwent abdominal operations were studied for three postoperative days to determine whether the postoperative neonatal renal response to fluid administration was appropriate or inappropriate. Each response was categorized, on the basis of urine and blood measurements, as: (1) appropriate urine output and concentration, (2) inappropriate urine output and concentration with fluid retention or (3) renal failure. Fluid intake was similar in all groups. The CDH group had a significantly lower urine output, higher urine osmolarity, and lower serum osmolarity. All of the control group (100%) responded appropriately to intake. Sixty-four percent of the CDH group inappropriately retained water during the first 16 hours (appropriate, 27%; renal failure, 9%). By 24 hours, 34% still had inappropriate urine output and fluid retention. The majority of patients with CDH initially responded inappropriately to postoperative fluid intake. If this response is not recognized and fluid intake is not adjusted, serious fluid overload will result.