Pilot trial to compare tolerance of chlorhexidine gluconate to povidone-iodine antisepsis for central venous catheter placement in neonates.

OBJECTIVE: The purpose of this pilot trial was to determine whether rates of contact dermatitis following cutaneous antisepsis for central catheter placement were similar among neonates treated with chlorhexidine gluconate and povidone-iodine. Chlorhexidine gluconate absorption was also evaluated. STUDY DESIGN: Infants weighing > or =1500 g and > or =7 days of age were randomized to a 10% povidone-iodine or 2% chlorhexidine gluconate site scrub before catheter placement. Primary outcomes evaluated included dermatitis, catheter colonization and chlorhexidine gluconate absorption. RESULT: A total of 48 neonates were enrolled. Colonization rates were similar among treatment groups (P<0.6). Dermatitis did not occur at chlorhexidine gluconate (central catheters, n=24; peripheral catheters, n=29) sites. Seven neonates had measurable chlorhexidine gluconate concentrations (range 13 to 100 ng ml(-1)) during catheterization. CONCLUSION: In this small trial chlorhexidine gluconate antisepsis was tolerated by study neonates. Chlorhexidine gluconate was cutaneously absorbed. Larger trials are needed to determine efficacy and tolerance of chlorhexidine gluconate in neonates.

Variability in the preoperative management of infants with hypoplastic left heart syndrome.

Infants with hypoplastic left heart syndrome (HLHS) commonly undergo initial surgical palliation during the first week of life. Few data exist on optimal preoperative management strategies; therefore, the management of these infants prior to surgery is anecdotal and variable. To more fully define this variability in preoperative care of infants with HLHS, a survey was designed to describe current preoperative management practices in the infant with HLHS. The questionnaire explored management styles as well as preoperative monitoring techniques and characteristics of the respondent's health care institution. The responses were compiled and are reported. A striking lack of consistency in preoperative management techniques for infants with HLHS is apparent. The impact of these preoperative strategies is unknown. Despite challenges in anatomic and hemodynamic variability at presentation, a prospective randomized controlled trial comparing ventilatory management techniques, enteral feeding strategies, and the utility of various monitoring tools on short- and long-term outcome is needed.

Ursodeoxycholic acid ameliorates ibuprofen-induced enteropathy in the rat.

BACKGROUND: The objective of the study was to determine whether ursodeoxycholic acid (Ursodiol) is protective against ibuprofen (IBU)-induced enteropathy. METHODS: Using the chronically catheterized rat model, IBU (60 mg/kg body weight per day) was infused via the gastric catheter twice daily. Pancreatic enzyme (PE; 10,000 U lipase/kg body weight per day) and Ursodiol (10 mg/kg body weight per day) in two doses were infused via the duodenal catheter. Rats were assigned to one of six treatment groups and were administered treatment for 20 days: control, IBU, PE, IBU + PE, IBU + Ursodiol, and IBU + PE + Ursodiol. The entire jejunum, ileum, cecum, and colon were available for histologic analysis using previously described techniques. RESULTS: Addition of Ursodiol to high-dose IBU and normal doses of PE showed a significant reduction in the percentage of rats with ulcers (P < 0.05), total number of serositis events (P < 0.01), total number of severe ulcers (P < 0.001), and an absence of ulcers in the large intestine. CONCLUSIONS: Ursodiol, the drug of choice for the treatment of cystic fibrosis liver disease, may offer a safe method of using high-dose IBU in these patients by ameliorating the enteropathy.

TNF-alpha increases sensitivity to LPS in chronically catheterized rats.

Patients with severe trauma injury are transiently exposed to increased serum concentrations of tumor necrosis factor-alpha (TNF-alpha). These patients are susceptible to the development of multisystem organ failure (MSOF) triggered by subsequent exposure to bacterial toxins either via infection or increased intestinal permeability. We simulated the cytokine response of trauma by infusing 0.8 or 8.0 microg/kg of TNF-alpha (priming dose) into chronically catheterized rats. After 48 h, rats were challenged with endotoxin [lipopolysaccharide (LPS); 10 or 1,000 microg/kg]. Animals primed with either dose of TNF-alpha and then challenged with 1,000 microg/kg of LPS demonstrated significantly increased mortality, mean peak serum concentrations of interferon-gamma (IFN-gamma), and blood lactate concentrations (P < 0.05) compared with nonprimed animals. Mean peak serum concentrations of IFN-gamma and blood lactate concentrations were increased after challenge with 10 microg/kg of LPS only in animals primed with 8.0 microg/kg of TNF-alpha. Priming with TNF-alpha did not increase mortality after challenge with 10 microg/kg of LPS. These data suggest that both TNF-alpha release and the subsequent exposure to bacterial toxins mediate the pathophysiological progression from trauma to subsequent MSOF.

Endotoxin-induced reduction in biliary indocyanine green excretion rate in a chronically catheterized rat model.

Using a nonstressed chronically catheterized rat model in which the common bile duct was cannulated, we studied endotoxin-induced alterations in hepatic function by measuring changes in the maximal steady-state biliary excretion rate of the anionic dye indocyanine green (ICG). Biliary excretion of ICG was calculated from direct measurements of biliary ICG concentrations and the bile flow rate during a continuous vascular infusion of ICG. Despite significant elevations in mean peak serum tumor necrosis factor-alpha (TNF-alpha) concentrations (90.9 +/- 16.2 ng/ml), there was no effect on mean rates of bile flow or biliary ICG clearance after administration of 100 microg/kg endotoxin at 6 or 24 h. Significant differences from mean baseline rates of bile flow and biliary ICG excretion did occur after administration of 1,000 microg/kg endotoxin (mean peak TNF-alpha 129.6 +/- 24.4 ng/ml). Furthermore, when rats were treated with up to 16 microg/kg of recombinant TNF-alpha, there was no change in mean rates of bile flow or ICG biliary clearance compared with baseline values. These data suggest that the complex regulation of biliary excretion is not mediated solely by TNF-alpha.

Staphylococcal enterotoxin B potentiates LPS-induced hepatic dysfunction in chronically catheterized rats.

Most models of liver dysfunction in sepsis use endotoxin (lipopolysaccharide; LPS) to induce a pathophysiological response. In our study published in this issue (Beno DWA, Uhing MR, Goto M, Chen Y, Jiyamapa-Serna VA, and Kimura RE. Am J Physiol Gastrointest Liver Physiol 280: G858-G865, 2001), the adverse effect of LPS on hepatic function in vivo was only significant at relatively high LPS doses despite high tumor necrosis factor-alpha concentrations. However, many patients with sepsis are exposed to multiple bacterial toxins that may augment the immune response, resulting in increased hepatic dysfunction. We have developed a model of polymicrobial sepsis by parentally administering a combination of staphylococcal enterotoxin B (SEB) and LPS. Using this model, we demonstrate that SEB (50 microg/kg) potentiates the effect of LPS-induced hepatic dysfunction as measured by decreased rates of biliary indocyanine green clearance and bile flow. These increases were most pronounced with doses of 10 and 100 microg/kg LPS, doses that by themselves do not induce hepatic dysfunction. This may explain the seemingly increased incidence and severity of liver dysfunction in sepsis, and it suggests that the exclusive use of LPS for replicating septic shock may not be relevant for studies of hepatic dysfunction.

The effect of surgical stress on the endotoxin-induced interferon-gamma response.

Most animal studies of cytokine release during sepsis or endotoxemia have used models in which studies are performed during or immediately after surgical stress. In a previous study, we showed that surgical stress as measured by elevated endogenous corticosterone concentrations attenuated the endotoxin-induced tumor necrosis factor alpha (TNFalpha) response. To determine whether surgical stress attenuates the endotoxin-induced interferon-gamma (IFN-gamma) response, chronically catheterized male Sprague-Dawley rats were treated with endotoxin 10 microg/kg immediately after surgery for catheter placement (surgical stress group, SS group) or at least 4 days postoperative (nonstressed group, NS group). We found that peak endotoxin-induced IFN-gamma responses were similar in the SS and NS groups (2094 +/- 315 pg/mL vs. 1863 +/- 307 pg/mL). Baseline corticosterone concentrations were significantly elevated in the SS group compared to the NS group (273.8 +/- 15.2 ng/mL vs. 30.0 +/- 8.5 ng/mL, P < 0.001). Peak TNFalpha concentrations were significantly reduced in the SS group compared to the NS group (5.2 +/- 1.9 ng/mL vs. 69.9 +/- 10.3 ng/mL, P = 0.0002). While peak serum TNFalpha concentrations were inversely related to baseline corticosterone concentrations, there was no correlation between peak IFN-gamma concentrations and baseline corticosterone concentrations or between TNFalpha and IFN-gamma concentrations. We conclude that surgical stress associated with elevated concentrations of endogenous corticosterone does not attenuate the endotoxin-induced IFN-gamma response despite an attenuation of the endotoxin-induced TNFalpha response. Because the effect of stress on different cytokines is varied, studies of sepsis and endotoxemia must account for the effects of experimentally-induced stress on cytokine responses.

The effects of high-dose ibuprofen and pancreatic enzymes on the intestine of the rat.

BACKGROUND: High-dose ibuprofen therapy limits the progression of lung disease in patients with cystic fibrosis. However, ibuprofen increases intestinal permeability, which potentiates intestinal damage caused by high-dose pancreatic enzyme treatment, as was shown in a previous study by this group. In the present study, the combined effects of ibuprofen and pancreatic enzyme treatment on the intestine and liver were examined. METHODS: Using a chronically catheterized rat model, high-dose ibuprofen (60 mg/kg x day in two doses), with or without pancreatic enzyme treatment was infused into gastric and duodenal catheters, respectively, for 20 days. Six groups were studied: control group; ibuprofen treatment alone; pancreatic enzyme treatment alone (two groups: normal dose, 10,000 U lipase/kg x day and high dose, 40,000 U lipase/kg x day); and ibuprofen combined with pancreatic enzyme (two groups: ibuprofen with high-dose pancreatic enzyme and ibuprofen and low-dose pancreatic enzyme). After treatment, rats were autopsied, and complete histologic analyses of the entire intestine and liver were performed. RESULTS: Ibuprofen caused mild ulceration of the small intestine in 50% of rats. Pancreatic enzyme treatment alone did not induce ulceration of the intestine. The combination of pancreatic enzyme and ibuprofen treatment increased the severity of the ulcers in the small intestine but not the number of ulcers or the percentage of rats affected. Ibuprofen treatment alone did not cause ulcers in the large intestine, but with the addition of pancreatic enzymes, ulceration and fibrosis were present. CONCLUSIONS: Ibuprofen at doses used to limit progression of cystic fibrosis lung disease caused enteropathy in 50% of rats. There was synergism between ibuprofen and pancreatic enzyme treatment in the production of severe ulcers. Ulcers in the cecum and colon were increased with combined ibuprofen and pancreatic enzyme treatment compared with incidence in control animals.

Effect of sodium ion coupled nutrient transport on intestinal permeability in chronically catheterised rats.

BACKGROUND: The significance of Nanutrient cotransport induced alterations in paracellular permeability is controversial. Most previous studies have measured intestinal permeability using in vitro methods or in vivo methods immediately after surgical bowel manipulation, and therefore may not be applicable to normal physiological conditions. AIMS: To determine whether activation of Na coupled nutrient transport increases intestinal permeability under normal physiological conditions. METHODS: The effect of Na-nutrient cotransport on intestinal permeability was measured in unrestrained, unanaesthetised, chronically catheterised male Sprague-Dawley rats using two different methods: measurement of the rate of absorption of passively absorbed hexoses, mannitol and L-glucose; and measurement of the mannitol:urea diffusion ratio. RESULTS: L-Glucose and mannitol absorption were not increased in the presence of D-glucose, alanine, maltose, or peptides. The mannitol:urea diffusion ratio was not increased by the presence of D-glucose. The presence of D-glucose in the intestinal lumen for 20 minutes did not alter intestinal permeability. CONCLUSIONS: Under normal physiological conditions, Na coupled nutrient transport does not increase intestinal permeability.

The effect of intestinal permeability on pancreatic enzyme-induced enteropathy in the rat.

BACKGROUND: Fibrosing colonopathy in cystic fibrosis occurs in children 2 to 7 years old and is associated with excess doses of high and regular strength lipase pancreatic enzymes, given for more than 6 months. A rat model was developed to study the effects of excessive doses of pancreatic enzymes equivalent to those producing fibrosing colonopathy in cystic fibrosis patients. METHODS: Five groups of animals were studied after administration of different combinations of pancreatic enzymes, oleic acid, and reserpine. RESULTS: Pancreatic enzymes alone produced minimal damage to the intestine and none to the liver. Excessive doses of pancreatic enzymes in combination with agents that increased intestinal permeability (oleic acid, reserpine) were associated with intestinal eosinophilia and necrosis of the jejunoileal muscle layer and inflammatory nodules in the liver, which increased with duration of insult. CONCLUSIONS: Increased intestinal permeability potentiates damage to the intestine caused by excessive pancreatic enzyme dosage. It is a characteristic of cystic fibrosis that may increase vulnerability to fibrosing colonopathy.

Intestinal absorption of proline and leucine in chronically catheterized rats.

BACKGROUND & AIMS: Most studies of intestinal amino acid absorption use methods in which intestinal function is studied immediately after surgical manipulation. The unphysiological experimental conditions present in these studies limit the ability to extrapolate their results to normal physiological conditions. The aim of this study was to determine the rates of proline and leucine absorption under normal physiological conditions. METHODS: Absorption of proline and leucine was measured in long-term catheterized rats using a method of dual infusion of radiolabeled isotopes. RESULTS: The maximum transport velocity and apparent membrane permeability for proline were 16.1 mumol/ min and 0.07 mumol.min-1.mmol/L-1. For leucine, the maximum transport velocity and apparent membrane permeability were 14.9 mumol/min and 0.08 mumol.min-1.mmol/L-1. Surgical bowel manipulation decreased the maximum transport velocities for proline and leucine by > 80%. The adverse effects of surgery were present for 24 hours. CONCLUSIONS: Under normal physiological conditions, most proline and leucine is absorbed by active transport. Measurements of amino acid absorption using methods in which the intestine has been surgically manipulated within the previous 24 hours significantly underestimate proline and leucine absorption and do not reflect absorption under normal physiological conditions.

The effect of surgical bowel manipulation and anesthesia on intestinal glucose absorption in rats.

The effects of surgical bowel manipulation and anesthesia on intestinal glucose absorption were determined in chronically catheterized rats. Total and passive rates of glucose absorption were measured using 3-O-methyl-glucose (3OMG) and L-glucose, metabolically inert analogues of D-glucose. The rates of 3OMG absorption immediately postoperative and 4 h later were 86 and 62% less than the absorption rate 6 d postoperative. The absorption rates of 3OMG 1 and 2 d postoperative were not different from 6 d postoperative. Absorption of L-glucose was not altered by bowel manipulation and anesthesia. Even after correction for the increased resistance of the unstirred water layer (UWL) after bowel manipulation, the rates of total and active intestinal glucose absorption immediately postoperative were only 11 and 15% of predicted rates of absorption. In chronically catheterized rats, > 75% of luminal 3OMG at a concentration of 400 mM was absorbed by active transport. The Km and Vmax of 3OMG active transport corrected for the resistance of the UWL were 11.3 mM and 15.6 mumoles/min, respectively. We conclude that measurements of intestinal glucose absorption performed within 24 h of surgical bowel manipulation greatly underestimate active absorption even if corrections are made to account for the increased resistance of the UWL.

Active transport of 3-O-methyl-glucose by the small intestine in chronically catheterized rats.

A method is described for determining the fraction of intestinal 3-O-methyl-glucose (3OMG) absorption that occurs by active transport in chronically catheterized rats without the influence of anesthesia or surgical bowel manipulation. That fraction was determined by simultaneously measuring portal venous-aortic blood concentration gradients (delta C) of 3-O-methyl-glucose (3OMG) and L-glucose, metabolically inert analogues of D-glucose. 3OMG is actively and passively absorbed by the same mechanisms as D-glucose, L-glucose is only passively absorbed. The fraction of 3OMG that is actively transported was calculated from the difference between 3OMG and L-glucose absorption, divided by total 3OMG absorption. We found that more than 94% of 3-O-methyl-glucose is absorbed by active transport when luminal concentrations range from 50 to 400 mM. We conclude that in unrestrained, unanesthetized chronically catheterized rats, most 3OMG is actively absorbed by the intestine even at high luminal concentrations.

Cyclosporin A-induced embryopathy in embryo culture is mediated through inhibition of the arachidonic acid pathway.

Embryos from Swiss Webster mice were grown in culture for 24 hr starting at Day 8.5 of gestation to study the effects of cyclosporin A (CsA) on the developing embryo. The embryos exposed to concentrations of CsA from 0.1 microgram/ml to 10.0 micrograms/ml developed a significant increase in the incidence of malformations from 28.6% to 78.6%, as compared with the 6.8% incidence of malformations in the control embryos. These malformations included defects in the neural tubes, head folds, and facial arches. In addition, inhibition of embryonic growth in CsA-exposed embryos was shown by a lower somite number, crown-rump length, and protein content than those of the control embryos. Supplementation of the culture medium with arachidonic acid or prostaglandin E2 decreased the incidence of CsA-induced malformations by 50% to 70% and prevented the CsA-induced inhibition of growth. We conclude that CsA causes abnormal embryonic development in mouse embryo culture and that the mechanism of CsA-induced embryopathy involves inhibition of the arachidonic acid pathway.

Value of amnioinfusion in reducing meconium aspiration syndrome.

Infusing normal saline into the uterine cavity, or amnioinfusion, is used to reduce the risk of meconium aspiration syndrome in babies born to women in whom the pregnancy is complicated by thick, meconium-stained amniotic fluid. In this retrospective review of 436 such pregnancies amnioinfusion was performed in 110. In 18.2% of infants in the amnioinfusion group meconium was found in the trachea compared with 29.1% of infants in the untreated group. In the treated group respiratory distress occurred in 2.7%, and meconium aspiration syndrome in 1.8%, whereas in the untreated group these frequencies were 10.1 and 5.5%, respectively. We conclude that saline amnioinfusion in pregnancies complicated by thick, meconium-stained amniotic fluid reduces the risk of respiratory distress in the newborn.

PGE2 prevents anomalies induced by hyperglycemia or diabetic serum in mouse embryos.

Both a high level of D-glucose in the medium and serum from a diabetic rat can induce neural-tube fusion defects and growth retardation in cultured mouse and rat embryos. To test our hypothesis that a deficiency of PGs may be involved in the mechanism of hyperglycemia- and diabetic serum-induced teratogenesis and growth retardation, we added PGE2 to the medium of a whole mouse embryo culture containing either normal rat serum and 52.7 mM D-glucose (hyperglycemic) or diabetic rat serum and 22.2 mM D-glucose (diabetic). After a 24-h culture, 94% of hyperglycemic embryos and 81% of diabetic embryos had neural-tube fusion defects; in addition, the number of somites, the morphological score, and the protein content of the embryos were significantly lower than those of controls. Supplementing the medium with PGE2 at concentrations of 0.028-28.4 nM (hyperglycemic) or 28.4 nM (diabetic) significantly reduced the incidence of neural-tube defects and increased the number of somites, the morphological score, and the protein content. These results strongly support the hypothesis that the teratogenicity of diabetic serum, as well as the teratogenic action of hyperglycemic culture, are mediated through a deficiency of PGs.