Selective decontamination in pediatric liver transplants. A randomized prospective study.

Although it has been suggested that selective decontamination of the digestive tract (SDD) decreases postoperative aerobic Gram-negative and fungal infections in orthotopic liver transplantation (OLT), no controlled trials exist in pediatric patients. This prospective, randomized controlled study of 36 pediatric OLT patients examines the effect of short-term SDD on postoperative infection and digestive tract flora. Patients were randomized into two groups. The control group received perioperative parenteral antibiotics only. The SDD group received in addition polymyxin E, tobramycin, and amphotericin B enterally and by oropharyngeal swab postoperatively until oral intake was tolerated (6 +/- 4 days). Indications for operation, preoperative status, age, and intensive care unit and hospital length of stay were no different in SDD (n = 18) and control (n = 18) groups. A total of 14 Gram-negative infections (intraabdominal abscess 7, septicemia 5, pneumonia 1, urinary tract 1) developed in the 36 patients studied. Mortality was not significantly different in the two groups. However, there were significantly fewer patients with Gram-negative infections in the SDD group: 3/18 patients (11%) vs. 11/18 patients (50%) in the control group, P < 0.001. There was also significant reduction in aerobic Gram-negative flora in the stool and pharynx in patients receiving SDD. Gram-positive and anaerobic organisms were unaffected. We conclude that short-term postoperative SDD significantly reduces Gram-negative infections in pediatric OLT patients.

Pure endotoxin does not pass across the intestinal epithelium in vitro.

Numerous reports suggest that endotoxin (LPS) may play a central role in triggering the inflammatory cascade that leads to the systemic inflammatory response syndrome. Although conditions that promote bacterial translocation in vivo may also facilitate direct translocation of LPS, the exact mechanisms by which LPS crosses the intestinal barrier to reach the systemic circulation are unknown. This study was designed to determine whether pure endotoxin could pass across injured rat ileal mucosa in the Ussing chamber. Sprague-Dawley rats were subjected to mild or severe hemorrhagic shock following carotid artery cannulation, and then resuscitated. Control animals underwent carotid artery cannulation only (sham-shock). Bacterial translocation to the mesenteric lymph nodes, liver, or spleen was measured after 24 h. Transmucosal passage of fluorescein isothiocyanate (FITC)-labeled E. coli C-25, or FITC-conjugated LPS was measured in the Ussing chamber. Intestinal membranes were examined by light and confocal laser microscopy. Severe hemorrhagic shock resulted in a 60% mortality rate and a 100% incidence of bacterial translocation in surviving animals. Sham-shock rats had a 100% survival rate and a 33% incidence of bacterial translocation. Transmucosal passage of FITC-E. coli C-25 was similar in both groups; however, passage of FITC-LPS was never detected. Histologic analysis confirmed mucosal injury to the intestinal epithelium of rats subjected to severe hemorrhagic shock, and confocal laser microscopy demonstrated passage of FITC-E. coil C-25, but not of FITC-LPS across the ileal membranes. Disruption of the intestinal epithelium with a potent mucolytic agent did not result in significant increase in transmucosal passage of FITC-LPS. We conclude that pure LPS does not pass across the intestinal mucosa in vitro. Transmucosal passage of LPS in vivo may be due, at least in part, to the release of bacterial cell wall fragments containing LPS from killed bacteria that had previously translocated.

Transmucosal passage of bacteria across rat intestinal epithelium in the Ussing chamber: effect of nutritional factors and bacterial virulence.

Transmucosal passage of bacteria across the intestine, the essential and prerequisite step for bacterial translocation, cannot be effectively studied using in vivo models of translocation. We have adapted the Ussing chamber into a fresh, sterile organ culture system that can facilitate the study of bacterial-epithelial interactions. Intestinal membranes were mounted in the Ussing chamber and perfused with a solution rich in putative mucosal micronutrients. The transmembrane potential difference was constantly monitored as a marker of intestinal integrity. Transmucosal passage of various bacteria across the normal intestinal epithelium was quantitated, and the mucosal membrane was examined by light and transmission electron microscopy. The addition of potassium cyanide to the mucosal perfusate resulted in an irreversible loss of potential difference. Oxygen deprivation also led to a precipitous drop in potential difference, but it was reversible with prompt reoxygenation. In contrast, intestinal membranes perfused with a solution consisting of Dulbecco's modified Eagle's medium + 20 mM glutamine maintained their potential difference for a sustained period (>180 min). Both the viability and structural integrity of the ileal intestinal membrane were maintained in culture ex vivo using this perfusate. Qualitative differences were observed in the mechanism of transmucosal passage of mild to moderately virulent bacteria such as Escherichia coli C-25 and Proteus mirabilis M-13, which pass through the intestinal epithelium without causing overt damage to the mucosa, and more virulent organisms such as Salmonella typhimurium, which cause extensive mucosal damage by light and transmission electron microscopy. The Ussing system should provide a useful model of intact organ culture for the study of the mechanisms of bacterial translocation and the pathogenesis of enteric infections.

The effects of a hyperosmolar intravenous contrast medium on blood viscosity.

The effects of the hyperosmolar contrast medium, diatrizoate meglumine (Renografin-76) on blood viscosity and other metabolic parameters were measured in 20 immature piglets. Intravenous contrast medium caused a significant (P less than .5) increase in serum osmolality, cardiac output, and urine output, and a decrease in hematocrit. There was a fall in blood viscosity that was not statistically significant. These changes, which are attributed to an acute shift of fluid into the hyperosmolar vascular compartment, were greatest at 3 minutes following injection and subsequently returned towards baseline levels. We conclude that blood viscosity is not increased following intravenous injection of hyperosmolar radiocontrast media.

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.

Role of intestinal mucus in transepithelial passage of bacteria across the intact ileum in vitro.

BACKGROUND: Although gastrointestinal mucus is one of a number of putative host defense mechanisms that protect the gut barrier against microbial translocation, little experimental data are available to show its role in this process. The present study sought to determine the role of mucus depletion on the transepithelial passage of bacteria across viable segments of rat ileum mounted in Ussing chambers in vitro. METHODS: Intestinal mucus was depleted in 12 rats after injection with pilocarpine (160 mg/kg intraperitoneally) 45 minutes before intestinal harvest. The mucosal surfaces of the perfused gut segments mounted in the Ussing chamber were exposed to 5 x 10(9) CFU/ml Escherichia coli C-25. Viability was monitored by continuous measurements of the potential difference generated by the membranes. The electrical characteristics were unaltered by pilocarpine pretreatment or exposure to bacteria. RESULTS: Bacterial passage occurred in 100% of pilocarpine membranes as compared with 33.3% in controls (p < 0.05). Pilocarpine-treated membranes resulted in 19.9 +/- 7.5 mg of retrievable mucus as compared with 28.8 +/- 7.2 mg in controls (p < 0.05). Light and transmission electron microscopy revealed an intact epithelial surface in all membranes. There was a marked decrease in mucus on the surface of pilocarpine-treated membranes. CONCLUSIONS: Intestinal mucus secretion is a critical factor in the barrier function of the gut, and its depletion results in a dramatic increase in bacterial passage across the intact rat ileum.

Immunoglobulin A supplementation abrogates bacterial translocation and preserves the architecture of the intestinal epithelium.

BACKGROUND: Breast milk has been shown to prevent gut-origin infections in neonates through undefined mechanisms. Putative protective factors in breast milk include immunoglobulin (Ig)A, IgG, and lactoferrin. We examined their role in bacterial translocation in neonatal rabbits. METHODS: IgA, IgG, and lactoferrin were isolated from rabbit breast milk through gel filtration and ion-exchange chromatography. Neonates were randomized to receive breast milk, formula alone, or formula supplemented with IgA, IgG, or lactoferrin. Quantitative cultures were performed on day 7 for bacterial translocation. Hematoxylin-eosin-stained sections of distal ileum were examined by light microscopy. Transmucosal bacterial passage was determined in vitro, and the ileal mucosal membranes were examined by confocal microscopy. RESULTS: IgA supplementation abrogated bacterial translocation. IgG and lactoferrin had no significant effect. Neonates that received IgA or breast milk gained more weight than those in the other groups. IgA reduced transmucosal bacterial passage in vitro. In contrast to the normal-appearing distal ileum of neonates fed breast milk, intestinal epithelium from neonates that received formula or formula with IgG or IgA demonstrated prominent vacuoles by light microscopy. Those fed formula alone or formula with lactoferrin had slightly shortened villi. CONCLUSIONS: IgA supplementation prevents bacterial translocation by enhancing gut mucosal barrier function.

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 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.

Quantitative and morphologic analysis of bacterial translocation in neonates.

OBJECTIVE: To elucidate the mechanisms of bacterial translocation in animals fed a conventional formula by correlating transmucosal bacterial passage in vitro with the structural characteristics of the neonatal intestinal mucosa. DESIGN: Newborn rabbits were randomized to receive a conventional formula or breast milk. Bacterial translocation to the mesenteric lymph nodes, liver, and spleen was quantitated after 7 days, and transmucosal passage of bacteria was measured in vitro using the Ussing chamber. The mucosal membranes were examined by light, transmission electron, and confocal laser scanning microscopy. RESULTS: Bacterial passage was rarely seen in the breast milk-fed animals in contrast to the formula-fed animals. Unlike the normal-appearing membranes from breast milk-fed animals, the epithelial cells of formula-fed animals were vacuolated but healthy, with normal polarization and microvillus border by confocal laser scanning microscopy. Villi of formula-fed animals were less densely packed than those of the breast milk-fed animals. Bacterial adhesion, internalization, and transmucosal passage were seen only in membranes from formula-fed animals. Transmission electron microscopy demonstrated bacteria incorporating into the epithelial surface through an active phagocytic process, with rearrangement of the actin cytoskeleton. Once internalized, these bacteria were seen within the cytoplasmic vacuoles and subsequently in the submucosa. No bacteria passed between epithelial cells. CONCLUSION: Morphological changes in the intestinal mucosa of formula-fed newborn rabbits may increase permeability to bacteria.

Inhibition of nitric oxide with aminoguanidine reduces bacterial translocation after endotoxin challenge in vivo.

BACKGROUND: Administration of lipopolysaccharide (LPS) has been shown to increase bacterial translocation (BT) in vivo and in vitro. In addition, LPS upregulates inducible nitric oxide synthase expression in the intestinal epithelium-a phenomenon that can either enhance microbial killing, or alternatively, promote BT by impairing the gut barrier. OBJECTIVE: To determine the effect, if any, of an inhibitor of nitric oxide synthase, namely, aminoguanidine (AG), on BT after LPS challenge. DESIGN: Sprague-Dawley rats were randomized to receive either AG or normal saline solution via subcutaneously placed osmotic pumps (Alzet), followed 18 hours later by LPS injection (5 mg/kg or 20 mg/kg intraperitoneally). Quantitative cultures of the cecum, mesenteric lymph nodes, liver, and spleen were obtained, and plasma nitrite and nitrate levels were measured at 24 hours. Transmembrane potential difference and mucosal permeability to fluorescein isothiocyanate-labeled dextran and fluorescein isothiocyanate-labeled Escherichia coli C25 were measured in the Using chamber. The intestinal membrane was examined by light, transmission electron, and confocal laser microscopy. RESULTS: Rats that were given high-dose LPS had elevated levels of nitrite and nitrate and a 100% incidence of BT. In contrast, AG infusion significantly reduced both BT (22%) and nitrite and nitrate levels. Animals that received LPS and normal saline solution had a significantly lower transmembrane potential difference than those that received LPS and AG. High-dose LPS resulted in sloughing of the apical enterocytes at the villus tips where bacterial entry seemed to occur, as seen with confocal laser microscopy. CONCLUSIONS: Inhibition of nitric oxide production with AG decreases BT after high-dose LPS challenge. The mechanism may involve increased cellular viability and decreased damage to the gut mucosal barrier in rats that receive AG.

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.

The last fifty years of neonatal surgical management.

Neonatal surgical mortality has steadily fallen over the last five decades. Improved survival does not appear to be related to the introduction of new operative procedures. Most of the basic procedures were developed by 1960. Eight developments appear to be responsible: (1) The growth of pediatric surgery resulted in widespread availability of neonatal surgeons and dissemination of knowledge about newborn surgical emergencies. (2) The parallel growth of pediatric anesthesia, beginning in 1946, provided specialized intraoperative management of the neonate. (3) Understanding neonatal physiology is the key to successful management; major advances occurred between 1950 and 1970. (4) New inventions revolutionized patient care; the transistor (1947) made it possible for medical devices to sense, amplify and control physiologic responses and opened the communication and computer age. (5) Neonatal mechanical ventilation had a prohibitive mortality and was seldom utilized; the development of CPAP and a continuous flow ventilator in the 1970s allowed safe ventilatory support. (6) Total parenteral nutrition (1968) prevented starvation that frequently affected infants with major anomalies. (7) The effective treatment of infection began with the clinical use of penicillin (1941); antibiotics have reduced mortality but infants suffering from the septic syndrome have a prohibitive mortality; cytokine, proinflammatory agent research, and the development of anti-inflammatory and blocking agents in the 1980s have not affected mortality. (8) The establishment of newborn intensive care units (1960) provided an environment, equipment, and staff for effective physiologic management.

Pathogenesis of pancreatic sepsis.

Although pancreatic sepsis is the most common cause of major morbidity and mortality associated with acute pancreatitis, the pathogenesis of such infections is unknown. Since intraperitoneal foci of inflammation are known to promote bacterial translocation, we hypothesized that acute pancreatitis promotes bacterial translocation that leads to infection of the inflamed pancreas and peripancreatic tissues. Non-lethal acute pancreatitis was induced in rats, and the translocation of live bacteria to the pancreas, mesenteric lymph nodes, liver, and spleen was determined. The presence of orally fed fluorescent beads, sensitive inert markers of translocation, was also determined in the pancreas and mesenteric lymph nodes. Live bacteria were recovered from 33% of the pancreata of rats with acute pancreatitis but from none of the control rats. Beads were visualized in 91% of the pancreata of rats with acute pancreatitis but in none of the pancreata from control rats. Beads were not visualized in the mesenteric lymph nodes of rats with acute pancreatitis, suggesting a transperitoneal route of migration. We conclude that acute pancreatitis promotes bacterial translocation leading to transperitoneal infection of the pancreas. These results support the use of selective decontamination of the gut and peritoneal lavage for the prevention of pancreatic infections in acute pancreatitis.

Inguinal hernia and hydrocele in infants and children.

Forty senior pediatric surgeons were surveyed regarding difficult decisions in the management of inguinal hernia. Areas covered were diagnosis, surgical techniques, hydrocele, incarceration, the contralateral side of a clinically apparent inguinal hernia, and inguinal hernia in the premature baby. The lack of agreement on many questions indicates that more than one approach may be effective in managing problems associated with hernia and that rigid policies are unwarranted.

Necrotizing enterocolitis.

Advances in neonatal care have resulted in an enlarging population of vulnerable premature newborns at risk for necrotizing enterocolitis (NEC). This article presents data supporting a unifying hypothesis for the initiation of NEC based on bacteria as the inciting agent(s), and the preterm baby as the vulnerable host. Facts and controversies concerning the pathology, microbiology, clinical presentation, management and outcome of infants afflicted with NEC are presented.

A critical appraisal of two common "neonatal" experiment subjects.

A comparative study of 11 physiologic variables in 200 piglets and puppies during the first 7 days of life was done. Seven of 11 physiologic variables significantly changed in the 1st wk of the piglets' life. Five of 11 variables significantly changed in the first week of the puppies' life. Six of 11 variables were significantly different when the newborn piglet was compared to the newborn puppy. The rate and/or direction of 7 of 11 physiologic changes during the first day of life were significantly different when the piglet was compared to the puppy. It was concluded that there are marked physiologic differences between: the newborn piglets and the 7 day old piglet; the newborn puppy and the 7 day old puppy; the newborn piglet and the newborn puppy and the "maturation" rate of the piglet and the puppy.

Transcutaneous oxygen monitoring in shock and resuscitation.

Transcutaneous oxygen tension (TcPO2), arterial oxygen tension, pulse, blood pressure, cardiac output and base excess or deficit were serially measured in 18 piglets, 7 to 14 days of age, subjected to a 35% hemorrhage and reinfusion of shed blood. Eight of 18 pigs died. There is a strong correlation between TcPO2 and PaO2 during normal flow, but a marked discrepancy develops during hemorrhage. Cardiac output, base deficit, and TcPO2 all follow a similar pattern during hemorrhage, but TcPO2 decreases more rapidly and remains at a low level in the nonsurviving animals. TcPO2, therefore, appears to be a sensitive, noninvasive indicator of low flow and the adequacy of resuscitation.

Distal neonatal intestinal obstruction: the choice of contrast material.

The use of barium sulfate as the contrast agent of choice in the radiographic evaluation of distal neonatal intestinal obstruction is advocated. The advantages of Gastrografin or other water-soluble contrast materials are far outweighed by their disadvantages, which include the hazards of hypertonic dehydration and the danger of missing the diagnosis of Hirschsprung's disease. Five patients are presented, all of whom had the diagnosis of Hirschsprung's disease missed in the neonatal period with one use of Gastrografin enemas. All five were subsequently admitted to the Surgical Neonatal Intensive Care Unit, critically ill with enterocolitis of Hirschsprung's disease.

Transepidermal water loss in the infant surgical patient.

Evaporative water loss from skin of the newborn surgical patient is a critical factor in overall water balance and an important source of heat loss. We studied 15 infant surgical patients under the following clinical conditions: (1) exposed babies; (2) infants covered by cloth drapes and lying on a cloth blanket; (3) infants covered by a plastic drape and lying on a cloth blanket; (4) babies lying on a plastic sheet and covered by a plastic sheet; and (5) infants placed in a plastic bag. This study demonstrated that evaporative water loss of the infant surgical patient can be significantly reduced by placing impermeable plastic sheets over and under the baby. This allowed water vapor to accumulate about the baby, increasing the relative humidity and reducing the evaporative water loss. An even further reduction in transepithelial water loss was accomplished by utilizing a plastic bag.