Does Use of a Feeding Protocol Change Outcomes in Gastroschisis? A Report from the Midwest Pediatric Surgery Consortium

INTRODUCTION

 Gastroschisis feeding practices vary. Standardized neonatal feeding protocols have been demonstrated to improve nutritional outcomes. We report outcomes of infants with gastroschisis that were fed with and without a protocol.

MATERIALS AND METHODS

 A retrospective study of neonates with uncomplicated gastroschisis at 11 children's hospitals from 2013 to 2016 was performed.Outcomes of infants fed via institutional-specific protocols were compared with those fed without a protocol. Subgroup analyses of protocol use with immediate versus delayed closure and with sutured versus sutureless closure were conducted.

RESULTS

 Among 315 neonates, protocol-based feeding was utilized in 204 (65%) while no feeding protocol was used in 111 (35%). There were less surgical site infections (SSI) in those fed with a protocol (7 vs. 16%, p = 0.019). There were no differences in TPN duration, time to initial oral intake, time to goal feeds, ventilator use, peripherally inserted central catheter line deep venous thromboses, or length of stay. Of those fed via protocol, less SSIs occurred in those who underwent sutured closure (9 vs. 19%, p = 0.026). Further analyses based on closure timing or closure method did not demonstrate any significant differences.

CONCLUSION

 Across this multi-institutional cohort of infants with uncomplicated gastroschisis, there were more SSIs in those fed without an institutional-based feeding protocol but no differences in other outcomes.

Immature teratoma in an adolescent with Proteus syndrome: A novel association

Proteus syndrome (PS) is a complex disorder characterized by variable clinical findings of overgrowth and tumor susceptibility. This report presents the first known association between PS and an ovarian germ cell tumor in an adolescent with immature teratoma. A review of the diagnosis of PS and associated tumors is included.

Pleuropulmonary Blastoma in Pediatric Lung Lesions

BACKGROUND

Pediatric lung lesions are a group of mostly benign pulmonary anomalies with a broad spectrum of clinical disease and histopathology. Our objective was to evaluate the characteristics of children undergoing resection of a primary lung lesion and to identify preoperative risk factors for malignancy.

METHODS

A retrospective cohort study was conducted by using an operative database of 521 primary lung lesions managed at 11 children's hospitals in the United States. Multivariable logistic regression was used to examine the relationship between preoperative characteristics and risk of malignancy, including pleuropulmonary blastoma (PPB).

RESULTS

None of the 344 prenatally diagnosed lesions had malignant pathology (P < .0001). Among 177 children without a history of prenatal detection, 15 (8.7%) were classified as having a malignant tumor (type 1 PPB, n = 11; other PPB, n = 3; adenocarcinoma, n = 1) at a median age of 20.7 months (interquartile range, 7.9-58.1). Malignancy was associated with the DICER1 mutation in 8 (57%) PPB cases. No malignant lesion had a systemic feeding vessel (P = .0427). The sensitivity of preoperative chest computed tomography (CT) for detecting malignant pathology was 33.3% (95% confidence interval [CI]: 15.2-58.3). Multivariable logistic regression revealed that increased suspicion of malignancy by CT and bilateral disease were significant predictors of malignant pathology (odds ratios of 42.15 [95% CI, 7.43-340.3; P < .0001] and 42.03 [95% CI, 3.51-995.6; P = .0041], respectively).

CONCLUSIONS

In pediatric lung masses initially diagnosed after birth, the risk of PPB approached 10%. These results strongly caution against routine nonoperative management in this patient population. DICER1 testing may be helpful given the poor sensitivity of CT for identifying malignant pathology.

Clinical outcomes following implementation of a management bundle for esophageal atresia with distal tracheoesophageal fistula

BACKGROUND/PURPOSE

This study evaluated compliance with a multi-institutional quality improvement management protocol for Type-C esophageal atresia with distal tracheoesophageal fistula (EA/TEF).

METHODS

Compliance and outcomes before and after implementation of a perioperative protocol bundle for infants undergoing Type-C EA/TEF repair were compared across 11 children's hospitals from 1/2016-1/2019. Bundle components included elimination of prosthetic material between tracheal and esophageal suture lines during repair, not leaving a transanastomotic tube at the conclusion of repair (NO-TUBE), obtaining an esophagram by postoperative-day-5, and discontinuing prophylactic antibiotics 24 h postoperatively.

RESULTS

One-hundred seventy patients were included, 40% pre-protocol and 60% post-protocol. Bundle compliance increased 2.5-fold pre- to post-protocol from 17.6% to 44.1% (p < 0.001). After stratifying by institutional compliance with all bundle components, 43.5% of patients were treated at low-compliance centers (<20%), 43% at medium-compliance centers (20-80%), and 13.5% at high-compliance centers (>80%). Rates of esophageal leak, anastomotic stricture, and time to full feeds did not differ between pre- and post-protocol cohorts, though there was an inverse correlation between NO-TUBE compliance and stricture rate over time (ρ = -0.75, p = 0.029).

CONCLUSIONS

Compliance with our multi-institutional management protocol increased 2.5-fold over the study period without compromising safety or time to feeds and does not support the use of transanastomotic tubes.

LEVEL OF EVIDENCE

Level II.

TYPE OF STUDY

Treatment Study.

Sutureless vs sutured abdominal wall closure for gastroschisis: Operative characteristics and early outcomes from the Midwest Pediatric Surgery Consortium

PURPOSE

To report outcomes of sutured and sutureless closure for gastroschisis across a large multi-institutional cohort.

METHODS

A retrospective study of infants with uncomplicated gastroschisis at 11 children's from 2014 to 2016 was performed. Outcomes of sutured and sutureless abdominal wall closure were compared.

RESULTS

Among 315 neonates with uncomplicated gastroschisis, sutured closure was performed in 248 (79%); 212 undergoing sutured closure after silo and 36 undergoing primary sutured closure. Sutureless closure was performed in 67 (21%); 37 primary sutureless closure, 30 sutureless closure after silo placement. There was no significant difference in gestational age, gender, birth weight, total days on TPN, and time from closure to initial oral intake or goal feeds. Sutureless closure patients had less general anesthetics, ventilator use/time, time from birth to final closure, antibiotic use after closure, and surgical site/deep space infections. Subgroup analysis demonstrated primary sutureless closure had less ventilator use and anesthetics than primary sutured closure. Sutureless closure after silo led to less ventilator use/time, anesthetics, and antibiotics compared to those with sutured closure after silo.

CONCLUSION

Sutureless abdominal wall closure of neonates with gastroschisis was associated with less general anesthetics, antibiotic use, surgical site/deep space infections, and decreased ventilator time. These findings support further prospective study by our group.

LEVEL OF EVIDENCE

Level III.

Development of a multi-institutional registry for children with operative congenital lung malformations

INTRODUCTION

The purpose of this study was to develop a multi-institutional registry to characterize the demographics, management, and outcomes of a contemporary cohort of children undergoing congenital lung malformation (CLM) resection.

METHODS

After central reliance IRB approval, a web-based, secure database was created to capture retrospective cohort data on pathologically-confirmed CLMs performed between 2009 and 2015 within a multi-institutional research collaborative.

RESULTS

Eleven children's hospitals contributed 506 patients. Among 344 prenatally diagnosed lesions, the congenital pulmonary airway malformation volume ratio was measured in 49.1%, and fetal MRI was performed in 34.3%. One hundred thirty-four (26.7%) children had respiratory symptoms at birth. Fifty-eight (11.6%) underwent neonatal resection, 322 (64.1%) had surgery at 1-12 months, and 122 (24.3%) had operations after 12 months. The median age at resection was 6.7 months (interquartile range, 3.6-11.4). Among 230 elective lobectomies performed in asymptomatic patients, thoracoscopy was successfully utilized in 102 (44.3%), but there was substantial variation across centers. The most common lesions were congenital pulmonary airway malformation (n = 234, 47.3%) and intralobar bronchopulmonary sequestration (n = 106, 21.4%).

CONCLUSION

This multicenter cohort study on operative CLMs highlights marked disease heterogeneity and substantial practice variation in preoperative evaluation and operative management. Future registry studies are planned to help establish evidence-based guidelines to optimize the care of these patients.

LEVEL OF EVIDENCE

Level II.

Review of Early Postoperative Metrics for Children Undergoing Resection of Congenital Pulmonary Airway Malformations and Report of Pleuropulmonary Blastoma at a Single Institution

PURPOSE

 The purpose of this study is to describe a single institution's 11-year experience treating children with congenital pulmonary airway malformations (CPAMs) and pleuropulmonary blastoma (PPB).

MATERIALS AND METHODS

 An institutional database was sampled for all patients aged 0 to 18 years from January 1, 2005, to December 31, 2015. Patients with a pathologic diagnosis of CPAM or PPB during this period were reviewed.

RESULTS

 A total of 51 patients with a pathologic diagnosis of CPAM (n = 45; 88.2%) or PPB (n = 6; 11.8%) underwent surgical resection. Among patients treated for PPB, one death occurred approximately 13 months after diagnosis. Although four patients with PPB (four out of six; 66.7%) had radiographic indicators highly suggestive of malignancy prior to surgery, two had a preoperative diagnosis of CPAM (two out of six; 33.3%). Twenty-four patients (24 out of 45; 53.3%) with CPAM underwent resection after developing symptoms and 21 (21 out of 45; 46.7%) were symptomatic at the time of surgery. Mann-Whitney's tests revealed a statistically significant difference in postoperative length of stay (median: 6 vs. 3 days; p < 0.001) and days with thoracostomy tube in place (median 3 vs. 2 days; p = 0.003) for symptomatic versus asymptomatic patients, respectively.

CONCLUSION

 CPAM patients appear to recover faster from surgery, if performed before the onset of symptoms. There may be a benefit to waiting until at least 3 months of age to complete resection in the asymptomatic patient. A low threshold for resection should be maintained in patients where delineating CPAM from PPB is difficult.

Proximal duodenal obstruction associated with compression from a replaced right hepatic artery

Replaced right hepatic artery is a well-described normal anatomical variant, not previously associated with acute or chronic abdominal symptoms or long-term sequelae. We report a 15-year-old girl presenting with nearly a decade of symptoms secondary to external compression of the proximal duodenum by the ventral passage of a replaced right hepatic artery. Surgical bypass of the duodenal obstruction significantly improved her symptoms. Replaced right hepatic artery related duodenal compression should be considered in the differential diagnosis of proximal duodenal obstruction. The presence of the replaced right hepatic artery should be clearly communicated to allow optimal presurgical planning.

Embryonic mouse blood flow and oxygen correlate with early pancreatic differentiation

The mammalian embryo represents a fundamental paradox in biology. Its location within the uterus, especially early during development when embryonic cardiovascular development and placental blood flow are not well-established, leads to an obligate hypoxic environment. Despite this hypoxia, the embryonic cells are able to undergo remarkable growth, morphogenesis, and differentiation. Recent evidence suggests that embryonic organ differentiation, including pancreatic β-cells, is tightly regulated by oxygen levels. Since a major determinant of oxygen tension in mammalian embryos after implantation is embryonic blood flow, here we used a novel survivable in utero intracardiac injection technique to deliver a vascular tracer to living mouse embryos. Once injected, the embryonic heart could be visualized to continue contracting normally, thereby distributing the tracer specifically only to those regions where embryonic blood was flowing. We found that the embryonic pancreas early in development shows a remarkable paucity of blood flow and that the presence of blood flow correlates with the differentiation state of the developing pancreatic epithelial cells in the region of the blood flow.

HPHT growth and x-ray characterization of high-quality type IIa diamond

The trend in synchrotron radiation (x-rays) is towards higher brilliance. This may lead to a very high power density, of the order of hundreds of watts per square millimetre at the x-ray optical elements. These elements are, typically, windows, polarizers, filters and monochromators. The preferred material for Bragg diffracting optical elements at present is silicon, which can be grown to a very high crystal perfection and workable size as well as rather easily processed to the required surface quality. This allows x-ray optical elements to be built with a sufficient degree of lattice perfection and crystal processing that they may preserve transversal coherence in the x-ray beam. This is important for the new techniques which include phase-sensitive imaging experiments like holo-tomography, x-ray photon correlation spectroscopy, coherent diffraction imaging and nanofocusing. Diamond has a lower absorption coefficient than silicon, a better thermal conductivity and lower thermal expansion coefficient which would make it the preferred material if the crystal perfection (bulk and surface) could be improved. Synthetic HPHT-grown (high pressure, high temperature) type Ib material can readily be produced in the necessary sizes of 4-8 mm square and with a nitrogen content of typically a few hundred parts per million. This material has applications in the less demanding roles such as phase plates: however, in a coherence-preserving beamline, where all elements must be of the same high quality, its quality is far from sufficient. Advances in HPHT synthesis methods have allowed the growth of type IIa diamond crystals of the same size as type Ib, but with substantially lower nitrogen content. Characterization of this high purity type IIa material has been carried out with the result that the crystalline (bulk) perfection of some of the HPHT-grown materials is approaching the quality required for the more demanding applications such as imaging applications and imaging applications with coherence preservation. The targets for further development of the type IIa diamond are size, crystal perfection, as measured by the techniques of white beam and monochromatic x-ray diffraction imaging (historically called x-ray topography), and also surface quality. Diamond plates extracted from the cubic growth sector furthest from the seed of the new low strain material produces no measurable broadening of the x-ray rocking curve width. One measures essentially the crystal reflectivity as defined by the intrinsic reflectivity curve (Darwin curve) width of a perfect crystal. In these cases the more sensitive technique of plane wave topography has been used to establish a local upper limit of the strain at the level of an 'effective misorientation' of 10(-7) rad.

Induction of fibroblast growth factor 10 (FGF10) in the ileal crypt epithelium after massive small bowel resection suggests a role for FGF10 in gut adaptation

We have previously reported that fibroblast growth factor 10 (FGF10) is crucial for the survival and proliferation of progenitor cells during embryonic gastrointestinal development. We sought to characterize the potential role of FGF10 signaling in the adaptive response following small bowel resection. Adult wild-type and Fgf10(LacZ) mice underwent 50% small bowel resection (SBR) or sham operation. Tissues were harvested 24 or 48 hr after surgery for histology, immunohistochemistry, and in situ hybridization. After SBR, Fgf10 expression was demonstrated in the epithelium at the base of the crypts. Moreover, there was a statistically significant increase in proliferating cells and goblet cells after SBR. In vitro studies using rat intestinal epithelial crypt (IEC-6) cells exposed to medium with or without recombinant FGF10 showed increased proliferation and phosphorylation of Raf and AKT with the addition of FGF10. Our results suggest that FGF10 may play a therapeutic role in diseases involving intestinal failure.

Primary gastric tumors of infancy and childhood: 54-year experience at a single institution

BACKGROUND/PURPOSE

Primary gastric tumors are rare in infancy and childhood. Because of the infrequent occurrence of these tumors, the clinician may be unfamiliar with optimal management strategies. We review our experience over the past 54 years and the current literature.

METHODS

During the period extending from 1952 to 2006, 21 infants and children with primary gastric tumors were treated at Children's Hospital Los Angeles. The series includes 8 cases previously reported and 13 additional cases seen since the initial report. Follow-up information is included.

RESULTS

There were 12 males and 9 females, aged 12 days to 18 years, who were diagnosed with gastric tumors. The patients presented primarily with weight loss, vomiting, or an abdominal mass. Morphological analysis revealed gastric stromal tumors (n = 6), teratomas (n = 4), lymphomas (n = 4), adenocarcinomas (n = 2), inflammatory myofibroblastic tumors (n = 2), embryonal rhabdomyosarcoma (n = 1), and hamartomas (n = 3). There were 16 patients still alive (mean follow-up, 22.3 months), whereas 6 died from active disease despite multimodal treatment. The deaths occurred in patients with stromal tumors, adenocarcinomas, lymphomas, and rhabdomyosarcoma.

CONCLUSIONS

Gastric tumors in children are rare. A high index of suspicion is needed to diagnose these tumors. Most malignant tumors present at an advanced stage and carry a substantial rate of mortality. They should be completely resected whenever feasible. In the case of some malignancies, chemotherapy may play a major role. Metastatic evaluation should be performed in all patients with malignant gastric tumors.

Interdisciplinary management of pediatric intestinal failure: a 10-year review of rehabilitation and transplantation

Management of children with intestinal failure is optimized by interdisciplinary coordination of parenteral and enteral nutrition support, medical management of associated complications, surgical lengthening procedures, and intestinal transplantation. Three hundred eighty-nine pediatric patients have been referred to our center for interdisciplinary assessment of intestinal failure since 1996 (median age=1 year; range 1 day-28.8 years). Factors predictive of weaning from parenteral nutrition without transplantation included increased mean bowel length for patients with gastroschisis (44 vs. 23 cm, p<0.05) and atresia (35 vs. 20 cm, p<0.01) and lower mean total bilirubin for patients with NEC (6.1 vs. 12.7 mg/dL, p<0.05). Others were also more likely to survive if referred with a lower mean total bilirubin (NEC, 7.9 vs. 12.7 mg/dL, p<0.05; pseudo-obstruction, 2.3 vs. 16.3 mg/dL, p<0.01). Patients weaned from parenteral nutrition by 2.5 years after referral achieved 95% survival at 5 years vs. 52% for those not weaned. Bowel lengthening procedures were performed on 25 patients. Eight subsequently weaned from parenteral nutrition without transplantation. Aggressive medical and nutritional intervention along with early referral, intestinal lengthening procedures, and intestinal transplantation in children with intestinal failure dependent on parenteral nutrition can result in the achievement of enteral autonomy and improved survival.

Treatment of infantile choriocarcinoma of the liver

Primary choriocarcinoma of the liver is an extremely rare childhood malignancy frequently associated with clinical instability at initial presentation. It often mimics other benign and malignant childhood liver tumors. Prompt diagnosis and initiation of treatment are necessary to attain a successful outcome. We describe a critically ill infant with metastatic choriocarcinoma whose diagnosis was based on radiographic and tumor marker findings, without an initial biopsy, and her successful management with neo-adjuvant chemotherapy and delayed surgery. She is currently in continuous remission 24 months from diagnosis.

Fibroblast growth factor 10 is required for survival and proliferation but not differentiation of intestinal epithelial progenitor cells during murine colon development

Epithelial-mesenchymal interactions that govern the development of the colon from the primitive gastrointestinal tract are still unclear. In this study, we determine the temporal-spatial expression pattern of Fibroblast growth factor 10 (Fgf10), a key developmental gene, in the colon at different developmental stages. We found that Fgf10 is expressed in the mesenchyme of the distal colon, while its main receptor Fgfr2-IIIb is expressed throughout the entire intestinal epithelium. We demonstrate that Fgf10 inactivation leads to decreased proliferation and increased cell apoptosis in the colonic epithelium at E10.5, therefore resulting in distal colonic atresia. Using newly described Fgf10 hypomorphic mice, we show that high levels of FGF10 are dispensable for the differentiation of the colonic epithelium. Our work unravels for the first time the pivotal role of FGF10 in the survival and proliferation of the colonic epithelium, biological activities which are essential for colonic crypt formation.

The fibroblast growth factor pathway serves a regulatory role in proliferation and apoptosis in the pathogenesis of intestinal atresia

BACKGROUND/PURPOSE

Intestinal atresia occurs in 1:5000 live births and is a neonatal challenge. Fibroblast growth factor receptor 2b (Fgfr2b) is a critical developmental regulator of proliferation and apoptosis in multiple organ systems including the gastrointestinal tract (GIT). Fgfr2b invalidation results in an autosomal recessive intestinal atresia phenotype. This study evaluates the role of Fgfr2b signaling in regulating proliferation and apoptosis in the pathogenesis of intestinal atresia.

METHODS

Wild-type and Fgfr2b-/- embryos were harvested from timed pregnant mice. The GIT was harvested using standard techniques. Terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling) was used to evaluate apoptosis and bromodeoxyuridine to assess proliferation by standard protocols. Photomicrographs were compared (Institutional Animal Care and Use Committee-approved protocol 32-02).

RESULTS

Wild-type and mutant GIT demonstrate that deletion of the Fgfr2b gene results in inhibition of epithelial proliferation and increased apoptosis. Inhibited proliferation and increased apoptosis are specific to those tissues of normal Fgfr2b expression, corresponding to the site of intestinal atresia.

CONCLUSIONS

The absence of embryonic GIT Fgfr2b expression results in decreased proliferation and increased apoptosis resulting in GIT atresia. The regulation of proliferation and apoptosis in intestinal cells as a genetically based cause of intestinal atresia represents a novel consideration in the pathogenesis of intestinal atresia.

Colonic atresia without mesenteric vascular occlusion. The role of the fibroblast growth factor 10 signaling pathway

BACKGROUND/PURPOSE

Colonic atresia occurs in 1:20,000 live births, offering a neonatal surgical challenge. Prenatal expression of fibroblast growth factor 10 (Fgf10), acting through fibroblast growth factor receptor 2b (Fgfr2b), is critical to the normal development of the colon. Invalidation of the Fgf10 pathway results in colonic atresia, inherited in an autosomal recessive pattern. Classically, disturbance of the mesenteric vasculature has been thought to cause many forms of intestinal atresia. The purpose of this study was to evaluate the role of vascular occlusion in the pathogenesis of colonic atresia.

METHODS

Wild type (Wt), Fgf10(-/-), and Fgfr2b(-/-) mutant mouse embryos were harvested from timed pregnant mothers. Immediately following harvest, filtered India ink was infused via intracardiac microinjection. The gastrointestinal tract was dissected, and photomicrographs of the mesenteric arterial anatomy were taken at key developmental time points.

RESULTS

Photomicrographs after India ink microinjections demonstrate normal, patent mesenteric cascades to the atretic colon at the time points corresponding to the failure of colonic development in the Fgf10(-/-) and Fgfr2b(-/-) mutants. The mesenteric arterial anatomy of the colon demonstrates no difference between the Wt and mutant colonic atresia.

CONCLUSIONS

The absence of embryonic expression of Fgf10 or its receptor Fgfr2b results in colonic atresia in mice. India ink microinjection is a direct measure of mesenteric arterial patency. Colonic atresia in the Fgf10(-/-) and Fgfr2b(-/-) mutants occurs despite normal mesenteric vascular development. Thus the atresia is not the result of a mesenteric vascular occlusion. The patent colonic mesentery of the Fgf10(-/-) and Fgfr2b(-/-) mutants challenges an accepted pathogenesis of intestinal atresia. Although colonic atresia can occur as a result of vascular occlusion, new evidence exists to suggest that a genetic mechanism may play a role in the pathogenesis of this disease.

Fibroblast growth factor-10 serves a regulatory role in duodenal development

PURPOSE

Duodenal obstruction occurs in 1 of 6000 live births and requires urgent surgical intervention. Duodenal atresia previously has been ascribed to a developmental failure of luminal recanalization; however, the cause of duodenal atresia remains incompletely understood. Although familial intestinal atresias have been described and syndromic associations are known, no specific genetic link has been established. Fibroblast growth factor-10 (Fgf10) is a known regulatory molecule relevant to mesenchymal-epithelial interactions, and mice deficient in Fgf10 demonstrate congenital anomalies in several organ systems including the gastrointestinal tract. The authors hypothesized that Fgf10 could serve a regulatory role in establishing normal duodenal development.

METHODS

Wild-type mice with beta-galactosidase under the control of the Fgf10 promoter were harvested from timed-pregnancy mothers. The expression of Fgf10 in the duodenum during development was evaluated by developing the embryos in X-Gal solution. Wild-type and mutant Fgf10(-/-) embryos were harvested from timed-pregnancy mothers at 18.5 days postconception (near term) and were analyzed for duodenal morphology (Institutional Animal Care and Use Committee-approved protocol 32-02). Photomicrographs were reviewed.

RESULTS

Fibroblast growth factor-10 is active in the duodenum at a late stage of development. The Fgf10(-/-) mutants demonstrate duodenal atresia with a variable phenotype similar to clinical findings. The duodenum fails to develop luminal continuity and has proximal dilation. The phenotype occurs in an autosomal recessive pattern with incomplete penetrance (38%).

CONCLUSIONS

Fibroblast growth factor-10 serves as a regulator in normal duodenal growth and development. Its deletion leads to duodenal atresia and challenges traditionally accepted theories of pathogenesis. This novel, genetically mediated duodenal malformation reflects an animal model that will allow further evaluation of the pathogenesis of this surgically correctable disease. By studying the mechanism of Fgf10 function in foregut development, the authors hope to better understand these anomalies and to explore possible therapeutic alternatives.

A genetic mechanism for cecal atresia: the role of the Fgf10 signaling pathway

BACKGROUND

Intestinal atresia represents a significant surgically correctable cause of intestinal obstruction in neonates. Intestinal development proceeds as a tube-like structure with differentiation along its axis. As the intestine differentiates, the cecum develops at the transition from small to large intestine. Fgf10 is known to serve a key role in budding morphogenesis; however, little is known about its role in the development of this transitional structure. Here we evaluate the effect of Fgf10/Fgfr2b invalidation on the developing cecum.

MATERIALS AND METHODS

Wild-type C57Bl/6, Fgf10(-/-), and Fgfr2b(-/-) embryos harvested from timed pregnant mothers were analyzed for cecal phenotype, Fgf10 expression, and differentiation of smooth muscle actin.

RESULTS

Wt cecal development is first evident at E11.5. FGF10 is discreetly expressed in the area of the developing cecum at early stages of development. One hundred percent of Fgf10(-/-) and Fgfr2b(-/-) mutant embryos demonstrate cecal atresia with absence of epithelial and muscular layers. The development of neighboring anatomical structures such as the ileocecal valve is not affected by Fgf10/Fgfr2b invalidation.

CONCLUSIONS

FGF10 expression is localized to the cecum early in the normal development of the cecum. Fgf10(-/-) and Fgfr2b(-/-) mutant embryos demonstrate cecal atresia with complete penetrance. Epithelial and muscular layers of the cecum are not present in the atretic cecum. The Fgf10(-/-) and Fgfr2b(-/-) mutants represent a genetically reproducible animal model of autosomal recessive intestinal atresia.

Fibroblast growth factor receptor 2 IIIb invalidation--a potential cause of familial duodenal atresia

BACKGROUND/PURPOSE

Duodenal atresia (DA) occurs in 1 in every 6,000 live births and represents a significant surgically correctable cause of intestinal obstruction in the neonate. Familial or congenital DA has been reported, implying that at least some cases of DA are the result of genetic, heritable abnormalities. The genes controlling duodenal development are incompletely understood. Fibroblast growth factor receptor 2IIIb (Fgfr2b) is known to play a critical role in the development of multiple organ systems including other gastrointestinal tract (GIT) structures. This study shows the key role of Fgfr2b in normal duodenal development and the pathogenesis of DA.

METHODS

Wild type (Wt) and Fgfr2b-/- embryos were harvested from timed pregnant mothers at stage E18.5 and were analyzed for duodenal phenotype.

RESULTS

Inactivation of Fgfr2b results in DA. DA is present in the Fgf2b-/- mutants with a 35% penetrance. The duodenal phenotype of the Fgf2b-/- mutants ranges from normal to a mucosal web, type I, and type III atresia.

CONCLUSIONS

Fgfr2b is a critical regulatory gene in the development of the duodenum. Fgfr2b invalidation (Fgfr2b-/- mutant) results in a reproducible, autosomal recessive duodenal atresia phenotype with incomplete penetrance and a variable phenotype.

Fibroblast growth factor 10 (Fgf10) invalidation results in anorectal malformation in mice

BACKGROUND/PURPOSE

Anorectal malformations occur in 1 per 4,000 live births and represent a surgical challenge. Although critically important, the basic mechanisms of normal anorectal union are incompletely understood. Fgf10 signaling is known to serve a key role in mesenchymal/epithelial interactions in many organ systems including the gastrointestinal tract (GIT). The authors therefore hypothesized that Fgf10 signaling has a central role in normal anorectal development.

METHODS

Fgf10 expression in wild-type (Wt) embryos was evaluated using whole-mount in situ hybridization. Wt and Fgf10-/- embryos were harvested from timed pregnant mothers at E12.5 through E17.5 and were analyzed for anorectal phenotype.

RESULTS

Wt development of union between anorectal structures is completed between E12.5 and E13.5 with luminal communication between distal rectal epithelium and anus. Fgf10 is discretely expressed at E12.5 in the distal rectum. Fgf10-/- mutants show failure of union of the rectum and anus at an early stage (E13.5) and near term (E17.5).

CONCLUSIONS

Fgf10 is expressed in the rectum at the time when anorectal continuity is established, indicating a role in normal anorectal development. Fgf10 invalidation (Fgf10-/- mutant) results in a genetically reproducible anorectal malformation phenotype. Fgf10 function is critical for normal anorectal development.

Requirement for fibroblast growth factor 10 or fibroblast growth factor receptor 2-IIIb signaling for cecal development in mouse

Epithelial-mesenchymal interactions are critical for the formation of gastrointestinal buds such as the cecum from the midgut, but the mechanisms regulating this process remain unclear. To investigate this problem, we have studied the temporal and spatial expression of key genes known to orchestrate branching morphogenesis. At E10.5, Fibroblast growth factor 10 (Fgf10) is specifically expressed in the mesenchyme above the future cecal epithelial bud, whereas Fgfr2b is found throughout the gut epithelium. From E11.5 onwards, Fgf10 expression is found throughout the cecum mesenchyme. Other relevant signaling molecules such as Sonic hedgehog, Wnt2b, and Tbx4 transcripts are found throughout the gut epithelium, including the cecum. Epithelial expression is also seen for Sprouty2, but only from E14.5 onwards. By contrast, Bone morphogenetic 4 (Bmp4) and Pitx2 are specifically expressed in the mesenchyme of the cecal bud at E11.5. Abrogation of either Fgf10 or Fgfr2b leads to similar phenotypes characterized by an arrest of epithelial invasion into the cecal mesenchymal tissue. However, a bud of undifferentiated cecal mesenchymal tissue is maintained throughout development. Our results further indicate that mesenchymal FGF10 acts mostly through the epithelial FGFR2b receptor; thereby triggering invasion of the midgut epithelium into the adjacent mesenchyme via an increased rate of epithelial proliferation at the tip of the cecum. Thus, FGF10 signaling via FGFR2b appears to be critical in the extension of the epithelium into the mesenchyme during cecal development.

Multiple trauma in children: critical care overview

Multiple trauma is more than the sum of the injuries. Management not only of the physiologic injury but also of the pathophysiologic responses, along with integration of the child's emotional and developmental needs and the child's family, forms the basis of trauma care. Multiple trauma in children also elicits profound psychological responses from the healthcare providers involved with these children. This overview will address the pathophysiology of multiple trauma in children and the general principles of trauma management by an integrated trauma team. Trauma is a systemic disease. Multiple trauma stimulates the release of multiple inflammatory mediators. A lethal triad of hypothermia, acidosis, and coagulopathy is the direct result of trauma and secondary injury from the systemic response to trauma. Controlling and responding to the secondary pathophysiologic sequelae of trauma is the cornerstone of trauma management in the multiply injured, critically ill child. Damage control surgery is a new, rational approach to the child with multiple trauma. The selection of children for damage control surgery depends on the severity of injury. Major abdominal vascular injuries and multiple visceral injuries are best considered for this approach. The effective management of childhood multiple trauma requires a combined team approach, consideration of the child and family, an organized trauma system, and an effective quality assurance and improvement mechanism.

Antibody blockade of ICAM-1 and VCAM-1 ameliorates inflammation in the SAMP-1/Yit adoptive transfer model of Crohn's disease in mice

BACKGROUND & AIMS

Integrins (alpha(4) and beta(2)) and their endothelial ligands vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) play key roles in leukocyte recruitment to areas of inflammation. ICAM-1 and VCAM-1 are expressed in inflamed intestinal tissues. This study investigates a possible causative role of adhesion molecules ICAM-1, VCAM-1, and alpha(4) integrins in mediating the inflammatory response in a murine model of Crohn's disease (CD).

METHODS

CD4+ mesenteric lymph node cells from SAMP-1/Yit donor mice were adoptively transferred into major histocompatibility complex-matched severe combined immunodeficiency disease mice. Six weeks later, these mice were left untreated or treated for 3 days with monoclonal antibodies (mAbs) to ICAM-1, VCAM-1, or both, and alpha(4), or both ICAM-1 and alpha(4), dexamethasone, or nonblocking isotype control antibodies. On day 4 after treatment, tissues were investigated for expression of ICAM-1, VCAM-1, and for severity of inflammation using a semiquantitative inflammatory score. Dexamethasone treatment resolved all measures of intestinal inflammation.

RESULTS

Blocking either ICAM-1, VCAM-1, or alpha(4) integrins had no significant beneficial effect. However, blocking ICAM-1 and alpha(4), or blocking ICAM-1 and VCAM-1, showed a 70% resolution of the active inflammation, but not chronic inflammation.

CONCLUSIONS

These findings suggest that blocking ICAM-1 and VCAM-1 may have therapeutic benefit for the acute inflammatory component of Crohn's disease.

Electrospray characterization of perrhenate systems

The electrospray negative ion mode (ESI-) mass spectrometry study of freshly prepared perrhenate in the ammonium and alkali metal (Na and K) solutions has been detailed. The cone voltage dependency of the negative ion abundance clearly indicates that the collision-activated dissociation (CAD) process in the cone-to-skimmer region is the source for both linear and non-linear cone voltage dependencies. The model also highlights that the [ReO2]- and [ReO3]- ions observed in the ESI- spectra are not present in the bulk, but are due to a dissociative collision, which strips a single oxygen atom from their precursor ions, namely [ReO3]- and [ReO4]- , respectively.

Pentapotassium dodecatungstoborate(III) hexadecahydrate

The title compound, K(5)[BW(12)O(40)].16H(2)O, contains a [BW(12)O(40)](5-) polyanion of 222 crystallographic symmetry, with a central tetrahedrally coordinated B(III) atom surrounded by four groups of three edge-sharing octahedra (W(3)O(13) subunits), which are linked in turn to each other and to the central BO(4) tetrahedron by shared O atoms at the vertices. There is a crystallographically unique B-O bond of 1.554 (10) A, while the average W-O distances are 2.344 (17) A for four coordinate O atoms, 1.917 (12) and 1.89 (2) A for two coordinate O atoms within and connecting the W(3)O(13) subunits, respectively, and 1.709 (8) A for terminal O atoms. Not all of the K(+) ions and H(2)O groups were located.

Follow-Up Abdominal Computed Tomography after Splenic Trauma in Children May Not be Necessary

Nonoperative management of splenic injuries in children is well accepted. However, the need for follow-up abdominal CT to document splenic healing has not been well studied. We retrospectively reviewed initial and follow-up abdominal CT examinations of pediatric patients admitted to our institution with documented splenic trauma who were managed nonoperatively. Eighty-four patients were admitted to our pediatric surgical service with splenic injury documented by CT from 1994 through 1998. The standard approach for splenic injury was bedrest for 5 to 21 days and limited activity for up to 90 days at the discretion of the attending surgeon. Thirty-five of the 84 had follow-up CTs during outpatient follow-up to evaluate and document splenic healing by CT criteria. The initial and follow-up studies were randomized and read blindly by pediatric radiologists using a modified American Association for the Surgery of Trauma grading system (I–V). The age range of the patients was 6 months to 17 years (mean ± SE; 11 ± 1 years). Nineteen (54%) were male and 16 (46%) were female. Causes of splenic trauma included motor vehicle accident (22), fall (seven), assault (four), pedestrian versus vehicle (one), and sports injury (one). Eight children (23%) had grade II injuries, 14 (40%) had grade III injuries, and 13 children (37%) had grade IV injuries on initial CT scan. Seven (88%) of the grade II splenic injuries were healed by 64 ± 11 days. The remaining grade II injury had healed by 210 days. Thirteen (93%) of the grade III splenic injuries were healed by 76 ± 7 days. The remaining grade III injury was healed by 140 days. Spleens in 10 (77%) of the 13 patients with grade IV injuries were healed by 81 ± 8 days. Of the three remaining grade IV injuries two were healed by 173 ± 14 days. The remaining patient's spleen was radiologically considered to have a grade III defect 91 days from the time of injury, and no further CTs were obtained. Of the 34 patients who underwent follow-up CT imaging until splenic healing was demonstrated the mean time to complete healing was 87 ± 8 days postinjury (range 11–217 days). These data suggest that routine follow-up abdominal CTs may not be necessary to allow children to resume their normal activities after an appropriate time of restricted activity.

Follow-up abdominal computed tomography after splenic trauma in children may not be necessary

Nonoperative management of splenic injuries in children is well accepted. However, the need for follow-up abdominal CT to document splenic healing has not been well studied. We retrospectively reviewed initial and follow-up abdominal CT examinations of pediatric patients admitted to our institution with documented splenic trauma who were managed nonoperatively. Eighty-four patients were admitted to our pediatric surgical service with splenic injury documented by CT from 1994 through 1998. The standard approach for splenic injury was bedrest for 5 to 21 days and limited activity for up to 90 days at the discretion of the attending surgeon. Thirty-five of the 84 had follow-up CTs during outpatient follow-up to evaluate and document splenic healing by CT criteria. The initial and follow-up studies were randomized and read blindly by pediatric radiologists using a modified American Association for the Surgery of Trauma grading system (I-V). The age range of the patients was 6 months to 17 years (mean +/- SE; 11 +/- 1 years). Nineteen (54%) were male and 16 (46%) were female. Causes of splenic trauma included motor vehicle accident (22), fall (seven), assault (four), pedestrian versus vehicle (one), and sports injury (one). Eight children (23%) had grade II injuries, 14 (40%) had grade III injuries, and 13 children (37%) had grade IV injuries on initial CT scan. Seven (88%) of the grade II splenic injuries were healed by 64 +/- 11 days. The remaining grade II injury had healed by 210 days. Thirteen (93%) of the grade III splenic injuries were healed by 76 +/- 7 days. The remaining grade III injury was healed by 140 days. Spleens in 10 (77%) of the 13 patients with grade IV injuries were healed by 81 +/- 8 days. Of the three remaining grade IV injuries two were healed by 173 +/- 14 days. The remaining patient's spleen was radiologically considered to have a grade III defect 91 days from the time of injury, and no further CTs were obtained. Of the 34 patients who underwent follow-up CT imaging until splenic healing was demonstrated the mean time to complete healing was 87 +/- 8 days postinjury (range 11-217 days). These data suggest that routine follow-up abdominal CTs may not be necessary to allow children to resume their normal activities after an appropriate time of restricted activity.

The role of peritoneal drainage for intestinal perforation in infants with and without necrotizing enterocolitis

BACKGROUND/PURPOSE

This report reviews our experience using peritoneal drainage (PD) as initial therapy for intestinal perforation in premature infants with and without necrotizing enterocolitis (NEC).

METHODS

A chart review was conducted of 18 consecutive premature infants who underwent PD for intestinal perforation from 1995 to 1998. Infants were divided into two groups. Group 1 consisted of eight infants who had intestinal perforation without evidence of NEC. Group 2 consisted of 10 infants who had perforation associated with evidence of NEC. A cohort of 10 infants with intestinal perforation treated with primary laparotomy between 1990 and 1995 was identified by chart review for historical control.

RESULTS

All infants improved immediately after PD. In group 1, all survived. Seven (88%) recovered systemically after PD. Of these, five (63%) never required laparotomy. Two (25%) required delayed laparotomy. One infant (12%) failed to continue to improve 48 hours after PD and underwent urgent laparotomy and recovered. In group 2, eight (80%) infants survived. Six (60%) recovered from NEC after PD, but five required delayed laparotomy for obstruction or persistent drainage. Four infants (40%) failed to progress from their initial improvement after PD. Three underwent laparotomy; two recovered and one had total intestinal necrosis and died. The fourth infant died without exploration and total intestinal necrosis was discovered during autopsy. Thus, seven of eight survivors (88%) in group 2 required laparotomy at some point in their course.

CONCLUSIONS

In premature infants with intestinal perforation, PD allows acute improvement and usually systemic recovery. In infants without evidence of NEC, PD may afford definitive treatment. In contrast, infants with evidence of NEC will likely require laparotomy, but initial PD may allow systemic stabilization and recovery of much of the involved intestine before laparotomy.

Diminished angiotensin-II and intact vasopressin response to hemorrhage in portal hypertension

Portal hypertension is characterized by splanchnic vasodilation and diminished arterial vasoconstrictor response to hemorrhage. Angiotensin-II and arginine vasopressin are critical modulators of the splanchnic response to hemorrhage in normal animals. We hypothesized that alterations in endogenous renin, angiotensin-II, or arginine vasopressin production or release could contribute to the abnormal response to hemorrhage in portal hypertension. Hemodynamics were studied in normal and portal hypertensive rabbits following either graded isovolumetric or single large volume hemorrhage, followed by reinfusion of blood. Hemodynamic and renin-angiotensin-II, and arginine vasopressin activities were determined. The experiments demonstrated a significantly diminished appearance in angiotensin-II (110.87+/-30 vs. 245+/-51.0 pg/mL) and aldosterone (54.2+/-9.5 vs. 119.4+/-13.5 ng/dL), and plasma renin activity (19.4+/-4.2 vs. 29.1+/-2.8 ng/mL/h) in portal hypertension compared with normal, but an appropriate rise in arginine vasopressin levels following hemorrhage in portal hypertension. These findings suggest a diminished angiotensin-II production or release in portal hypertension, which may mediate the failure of the appropriate splanchnic vasoconstrictive response to hemorrhage.

Rectal squamous mucosectomy and ileal anal pull-through procedures: single surgeon experience in 105 patients

BACKGROUND

The ileal anal pull-through procedure has become the most frequently used cointinence sparing procedure for patients with ulcerative colitis or familial polyposis. Areas of controversy concern the use of temporary ileostomies, and the extent of the rectal mucosectomy. The current report presents a single surgeon's experience with mucosectomy to the perianal skin (squamous mucosectomy), with ileal J-pouch reservoir construction and temporary ileostomy.

METHODS

We reviewed the records of 105 consecutive patients undergoing this procedure by a single surgeon during a 5-year period. One hundred percent follow-up was achieved.

RESULTS

There was 100% gross fecal continence, with 5% of patients expressing rare day time leakage, and 28% having intermittent nocturnal leakage. There were no instances of pelvic sepsis, and no pouches have been removed. The diverting ileostomy was associated with 6% morbidity.

CONCLUSIONS

We conclude that the rectal mucosectomy can be safely extended to the levels of perianal skin with no loss in continence or function. We recommend that this be adopted as the standard for this procedure to ensure complete eradication of the underlying pathologic condition.

Loss of angiotensin-II receptors in portal hypertensive rabbits

Decreased splanchnic vascular response to exogenous angiotensin-II (A-II) infusion in portal hypertension has recently been documented. A-II receptor density and binding affinity in the mesenteric artery, portal vein, and adrenal gland of normal and portal hypertensive rabbits were studied. Portal hypertension was induced by partial portal vein ligation 3 weeks before study. There were no significant differences in serum concentrations of sodium, potassium, A-II, serum osmolality, or hematocrit between normal and portal hypertensive rabbits. The portal hypertensive portal vein exhibited a 60% fall in A-II receptor number from 65.1 +/- 0.3 fmol/mg in normal to 27.0 +/- 8 fmol/mg (P < .05) in portal hypertension. A significant decrease in receptor number occurred in the portal hypertensive mesenteric artery, 224 +/- 39 fmol/mg compared with 345 +/- 45 fmol/mg in normal rabbits, and in the adrenal cortex 6.8 +/- 1.3 pmol/mg compared with 12.1 +/- 2.5 pmol/mg in normal controls (P < .05). No significant difference in A-II receptor affinity was observed in tissues studied between normal and portal hypertensive rabbits. Autoradiographic study on A-II receptors was consistent with data from membrane binding assays. Receptor subtype analysis showed exclusive type I receptor binding in the mesenteric artery and portal vein. We conclude there is a global reduction in the A-II receptor number in portal hypertension that may mediate much of the decreased response to A-II seen in this disorder. This loss of the A-II receptor may partially explain hemodynamic derangements peculiar to portal hypertension.

Role of cirrhosis in the hemodynamic response to hemorrhage in portal hypertension

BACKGROUND

We studied hemodynamic alterations in normal and three models of portal hypertension at rest, after hemorrhage, and after resuscitation to determine the role of hepatic dysfunction in the splanchnic vascular response to hemorrhage in portal hypertension.

METHODS

One noncirrhotic and two cirrhotic models of portal hypertension were produced in rabbits: partial prehepatic portal vein ligation, common bile duct ligation, and carbon tetrachloride-induced cirrhosis. Animals were subjected to isovolemic hemorrhage followed by reinfusion of shed blood. Portal, central, and aortic pressures, superior mesenteric artery blood flow, and portosystemic shunt were measured.

RESULTS

Histologic examination showed parenchymal damage was absent in normal and portal vein ligation, severe in common bile duct ligation, and moderate in carbon tetrachloride-induced cirrhosis. All portal hypertensive animals exhibited diminished splanchnic vasoconstrictive response to hemorrhage compared with normal. The carbon tetrachloride cirrhosis group had severe cirrhotic changes, minimal portosystemic shunt, and mildly diminished constrictive response. In contrast, the portal vein ligation and common bile duct ligation animals had larger portosystemic shunts, markedly diminished constrictive response, and less severe parenchymal damage. A direct correlation existed between magnitude of rise in portal venous pressure or degree of portosystemic shunt and the fall in mesenteric resistance or diminution of vasoconstrictive response to hemorrhage.

CONCLUSIONS

We concluded that the abnormal splanchnic vascular response in portal hypertension is relatively independent of the degree of hepatic parenchymal injury, but it is related to the degree of portal hypertension and possibly to splanchnic hyperemia.

Effects of nitric oxide and cyclooxygenase inhibition on splanchnic hemodynamics in portal hypertension

Portal hypertension is associated with splanchnic hyperemia and increased plasma levels of prostacyclin. Recently, nitric oxide was proposed as a mediator of this arterial vasodilatation. We hypothesized that portal hypertension alters the relative contribution of prostacyclin and nitric oxide to splanchnic vasomotor control. We studied the relationship of nitric oxide and prostaglandins in normal and portal-hypertensive (3 wk after partial portal vein ligation) male rabbits at baseline and following increasing doses of indomethacin, LG-nitro-L-arginine methylester or both. L-arginine was used as the control. Aortic, central and portal venous pressures were measured directly. Blood flow in the superior mesenteric artery was measured by means of an ultrasonic flow probe, and resistance was calculated. LG-nitro-L-arginine methylester produced vasoconstriction (increased resistance and decreased blood flow in the superior mesenteric artery) in normal and portal-hypertensive rabbits, although in portal hypertensive animals resistance and superior mesenteric artery blood flow remained significantly different than that in normal rabbits because of preexisting hyperemia. L-arginine reversed the effect of LG-nitro-L-arginine methylester. Cyclooxygenase blockade induced dose-dependent vasoconstriction in normal and portal-hypertensive animals. Indomethacin induced further vasoconstriction after LG-nitro-L-arginine methylester and reduced portal venous pressure in portal-hypertensive animals. We conclude that this indicates an amplified role for some prostaglandin, probably prostacyclin, in portal hypertension hemodynamics. It also implies that the two vasodilators act by way of independent mechanisms.

Regional chemotherapy devices: effect of experience and anatomy on complications

PURPOSE

Regional hepatic arterial infusion (HAI) devices have been used for 17 years, but reports of unacceptably high complication rates have led to controversy about their use. Inadequate or misdirected infusion has been reported to occur in up to 45% of patients. We evaluated whether surgeon experience or presence of variant arterial anatomy related to risk of coagulation.

MATERIALS AND METHODS

We reviewed 70 patients undergoing placement of HAI catheters. Surgeons were classed as experienced after 10 procedures and arterial anatomy was evaluated angiographically with confirmation at operation. Complications were categorized as technical (17%) or chemotherapy-related (16%).

RESULTS

Inexperienced surgeons had a technical complication rate of 37% (80% of the patients involved had standard anatomy), while experienced surgeons had a technical complication rate of 7% (P < .01). Experienced surgeons had no complications in patients with standard anatomy, while inexperienced surgeons had a 42% (eight of 19) complication rate in similar patients (P < .01).

CONCLUSION

We conclude that technical complications are closely associated with surgeon experience and arterial anatomy.

Long-term central venous access vs other home therapies: complications in patients with acquired immunodeficiency syndrome

One hundred and forty silicone catheters were inserted in 127 patients for long-term intravenous access with a cumulative follow-up time of 21,125 catheter-days (58 patient-years). Fifty-six patients had acquired immunodeficiency syndrome (AIDS); 44 were not AIDS patients and were receiving ambulatory home parenteral nutrition, whereas the remaining 27 did not have AIDS and were receiving home antibiotic therapy. Patients had a mean of 1.1 catheters inserted, and the rate of Hickman catheter-related sepsis was 0.18 per 100 catheter days or 0.6 septic episodes per patient year of treatment. Catheter-related sepsis was higher in AIDS patients (p < .01) and in patients receiving parenteral nutrition (p < .05) compared with those receiving antibiotic therapy. Prior catheter infection and AIDS were the most significant predictors of catheter infection (p < .01). Staphylococcus aureus was the most commonly isolated pathogen (61%) in AIDS patients. Fever (p < .001) and relative leukocytosis (p < .02) were the most common signs of infection. Only 14 infected catheters (37.8%) were salvaged by antibiotic therapy after the initial infection episode, and 6 of these catheters (42.9%) had recurrent multiple infections. In addition, inflammatory bowel disease was found to be a risk factor for venous thrombosis (p = .018). We conclude that because immunocompromised patients have a high risk of infection, catheter-related sepsis in these patients should be treated by catheter removal and antibiotics.

Oxidation of Nickel(II) and Manganese(II) by Peroxodisulfate in Aqueous Solution in the Presence of Molybdate. Crystal Structure of the (NH4)6[NiMo9O32].6H2O Product

Oxidation of Ni2+,aq, by S2O82- to nickel(IV) in the presence of molybdate ion, as in the analogous manganese system, involves the formation of the soluble heteropolymolybdate anion [MMogO32]2- (M = Ni, Mn ). The nickel(IV) product crystallized as (NH4)6 [NiMogO32].6H2O from the reaction mixture in the rhombohedra1 space group R3, a 15.922(1), c 12.406(1) � ; the structure was determined by X-ray diffraction methods, and refined to a residual of 0.025 for 1741 independent 'observed' reflections. The kinetics of the oxidation were examined at 80 C over the pH range 3.0-5.2; a linear dependence on [S2O82-] and a non-linear dependence on l/[H+] were observed. The influence of variation of the Ni/Mo ratio between 1:10 and 1:25 on the observed rate constant was very small at pH 4.5, a result supporting the view that the precursor exists as the known [NiMo6O24H6]4- or a close analogue in solution. The pH dependence of the observed rate constant at a fixed oxidant concentration (0.025 mol dm-3) fits dequately to the expression kobs = kH [H+]/(Ka+[H+]) where kH = 0.0013 dm3 mol-1 s-1 and Ka = 4-0x10-5. The first-order dependence on peroxodisulfate subsequently yields a second-order rate constant of 0.042 dm3 mol-1 s-1. Under analogous conditions, oxidation of manganese(II) occurs eightfold more slowly than oxidation of nickel(II), whereas oxidation of manganese(II) by peroxomonosulfuric acid is 16-fold faster than oxidation by peroxodisulfate under similar conditions.

Oxidation of Manganese(II) by Peroxomonosulfuric Acid in Aqueous Solution in the Presence of Molybdate. Crystal-Structure of the K6[MnMo9O32].6H2O Product

Oxidation of Mn2+aq by HSO5- to manganese(IV) in the presence of molybdate ion in acetate buffer involves the formation of the soluble heteropolymolybdate anion [MnMo9O32]6-. This was crystallized as K6[MnMo9O32].6H2O from the reaction mixture in the rhombohedra1 space group R32, a 15.569(1), c 12.432(1) � , and the structure was determined by X-ray diffraction methods, refined to a residual of 0.028 for 1032 independent 'observed' reflections. Unlike the oxidation reaction in the absence of molybdate , which displays classical autocatalytic kinetics and generates manganese dioxide, no MnO2 is formed with Mn /Mo ≤ 1:12, the red heteropolymolybdate being the only isolated product. The kinetics of the oxidation were examined at 40�C over the pH range 4.0-5.3, and non-linear dependences on [HSO5-] and l/[H+] observed. The influence of variation of the manganese-to-molybdenum ratio between 1 : 12 and 1 : 50 on the observed rate constant was very small at pH 4.54, a result supporting the view that the manganese exists initially as the known [MnMo6O24H6]4- or a close analogue in solution. A rate expression of the form -d[Mn11dt = ko [HSO5-]+ k1 [HSO5-]2 where k0 = 0.021 dm3 mol-1 s-1 and k1 = 0.041 dm6 mol-1s-1 was observed at pH 4.54. Cyclic voltammetry identified the oxidation of the manganese(II) cluster as an irreversible process which occurs at +1.035 V (v. Ag/ AgCl ) at pH 3.95, becoming progressively more negative with increasing pH (+0.84 V at pH 5.3), the variation presumably related to variation in protonation of the cluster, which also governs the non-linear dependence of the chemical oxidation on [H+].

Synthetic diamonds as in vivo radiation detectors

Synthetic diamonds with controlled amounts of impurity atoms can be manufactured so that, as thermoluminescent dosimeters, they can be made to have sensitivities at least as good as presently available commercial thermoluminescent dosimeters. They also exhibit, for radiations normally found in therapy situations, a linearity of response that extends from less than 0.01 Gy (1 rad) to over 10 Gy (1000 rad). Their physical size and form, crystals which can have volumes of less than 1 mm3, make them ideal candidates for in vivo monitoring of radiation fields, particularly electron fields where high-resolution measurements are essential for accurate isodose line determinations. Aspects of dose response from gamma-ray beams in relation to the type and concentrations of the impurity atoms within the diamond are discussed, and some experimental values for gamma, x-ray, and electron beams are presented.

Synthetic diamonds as ionisation chamber radiation detectors in biological environments

Synthetic diamonds with nitrogen concentrations higher than previously reported in the literature are found to operate very effectively as alpha-particle detectors, as well as detectors for gamma radiation, when operated as ionisation chambers. Certain of the specimens exhibited extensive linear response characteristics when subjected to either alpha particles or gamma radiation of various dose rates. For alpha particles, the response of the detectors at constant particle flux was also found to increase linearly with increasing alpha-particle energy. Unlike previously reported investigations, however, the variation in the response of the synthetic stones to gamma radiation as a function of time was found to be not only more rapid but also to be virtually unaffected by illumination with intense white light.