Modeling of heterotrophic bacteria counts in a water distribution system

Heterotrophic plate count (HPC) constitutes a common indicator for monitoring of microbiological water quality in distribution systems (DS). This paper aims to identify factors explaining the spatiotemporal distribution of heterotrophic bacteria and model their occurrence in the distribution system. The case under study is the DS of Quebec City, Canada. The study is based on a robust database resulting from a sampling campaign carried out in about 50 DS locations, monitored bi-weekly over a three-year period. Models for explaining and predicting HPC levels were based on both one-level and multi-level Poisson regression techniques. The latter take into account the nested structure of data, the possible spatiotemporal correlation among HPC observations and the fact that sampling points, months and/or distribution sub-systems may represent clusters. Models show that the best predictors for spatiotemporal occurrence of HPC in the DS are: free residual chlorine that has an inverse relation with the HPC levels, water temperature and water ultraviolet absorbance, both having a positive impact on HPC levels. A sensitivity analysis based on the best performing model (two-level model) allowed for the identification of seasonal-based strategies to reduce HPC levels.

A methodology for identifying vulnerable locations to taste and odour problems in a drinking water system

In this research, methodology was developed to identify locations vulnerable to taste and odour problems in a distribution system. The methodology was based on a multicriteria procedure combining spatial information on consumer complaints and popular perception of tap water. The first step in the described methodology consisted of mapping complaints regarding tap water made by the population between 2002 and 2004 using a geographical information system (GIS). The second step consisted of analysing results of a questionnaire-based mail survey, also through GIS. The information generated using the above steps was integrated using a multicriteria and spatial approach allowing segregation of the distribution system into delineated zones, according to their vulnerability to occurrences of taste and odour problems. The identification of vulnerable sectors in a distribution system will help water managers to implement a better-targeted water quality monitoring programme--one that considers odours and tastes of drinking water--within the management process.

Involvement of the fractalkine pathway in the pathogenesis of childhood hemolytic uremic syndrome

Thrombotic microangiopathy and acute renal failure are cardinal features of postdiarrheal hemolytic uremic syndrome (HUS). These conditions are related to endothelial and epithelial cell damage induced by Shiga toxin (Stx) through the interaction with its globotriaosyl ceramide receptor. However, inflammatory processes contribute to the pathogenesis of HUS by sensitizing cells to Stx fractalkine (FKN), a CX(3)C transmembrane chemokine expressed on epithelial and endothelial cells upon activation, is involved in the selective migration and adhesion of specific leukocyte subsets to tissues. Here, we demonstrated a selective depletion of circulating mononuclear leukocytes expressing the receptor for FKN (CX(3)CR1) in patients with HUS. We found a unique phenotype in children with HUS distinct from that seen in healthy, uremic, or infected controls, in which monocytes lost CX(3)CR1, down-modulated CD62L, and increased CD16. In addition, the CD56(dim) natural killer (NK) subpopulation was decreased, leading to an altered peripheral CD56(dim)/CD56(bright) ratio from 10.0 to 4.5. It is noteworthy that a negative correlation existed between the percentage of circulating CX(3)CR1(+) leukocytes and the severity of renal failure. Finally, CX(3)CR1(+) leukocytes were observed in renal biopsies from patients with HUS. We suggest that the interaction of CX(3)CR1(+) cells with FKN present on activated endothelial cells may contribute to renal injury in HUS.

Effects of indoor drinking water handling on trihalomethanes and haloacetic acids

In this study, different tap water handling strategies were investigated to evaluate the effects on two principal chlorinated DBPs, trihalomethanes (THMs) and haloacetic acids (HAAs). Tap water samples collected in the Quebec City (Canada) distribution system on a spatio-temporal basis were subjected to diverse indoor handling scenarios: storing water in the refrigerator, boiling water followed by storage and, finally, filtering water with a point-of-use commercial pitcher also followed by storage. In the first two cases, the use of covered and uncovered pitchers was investigated separately, while in the last case, both the use of new and used filters was compared. In all cases, maximum storage time was 48h. Results demonstrated that in some cases, water handling scenarios have considerable effect, and in other cases, little or no effect. Removal of THM concentrations by simple storage was high (on average 30%) and very high by boiling and filtering with subsequent storage in the refrigerator (on average, 87% and 92%, respectively). In scenarios where water was stored in uncovered pitchers (with or without previous boiling and filtering), the THM decrease was higher for increased storage times. However, storage did not have any effect on HAAs, whereas boiling decreased levels of trichloroacetic acid (TCAA) (on average 42%) and increased levels of dichloroacetic acid (DCAA) (on average 35%), resulting in unchanged average levels of total HAAs. The use of the filtration pitcher decreased HAA levels dramatically (on average 66%). Percentages of change in chlorinated DBPs in the different scenarios varied according to initial concentrations in tap water (baseline water), that is, according to the spatio-temporal variations of these substances in the distribution system. On the basis of these results, the paper discusses implications regarding public health protection and exposure assessment for epidemiological studies.

Procalcitonin in children with Escherichia coli O157:H7 associated hemolytic uremic syndrome

Shiga toxin producing Escherichia coli (STEC) are noninvasive enteric pathogens that may cause hemorrhagic colitis (HC) and diarrhea-associated hemolytic uremic syndrome (D+ HUS). We hypothesized that development of D+ HUS is associated with increased serum procalcitonin (PCT) levels. PCT was measured by an immunoluminometric assay in 113 patients. Concentrations of PCT were different in normal controls, disease control groups (rotavirus enteritis, HC due to non-STEC pathogens, chronic renal failure), and children with uncomplicated O157:H7 HC or D+ HUS. Children with D+ HUS showed higher PCT levels than those with uncomplicated O157:H7 HC, and increased concentrations were noted in cases requiring peritoneal dialysis. Severely increased concentrations were observed in children with D+ HUS on d 5 or 6 after the onset of enteritis, whereas serial measurements in those with uncomplicated O157:H7 HC remained within the normal range throughout the first week of illness. PCT was correlated with serum concentrations of lipopolysaccharide (LPS)-binding protein and serum levels of alanine aminotransferase. Using two separate sets of real-time PCR primers, we were unable to detect elevated PCT mRNA transcripts in nonadherent undifferentiated (monocytic) or differentiated (macrophage-like) THP-1 cells stimulated with purified Shiga toxin-1 and/or LPS. Our data show that serum levels of PCT are associated with the severity of illness in children with D+ HUS. Further studies are needed to determine the role of PCT in the pathogenesis of thrombotic microangiopathy associated to childhood D+ HUS.

Induction of apoptosis by herpes simplex virus-1 in neonatal, but not adult, neutrophils

We report a study on the effect of herpes simplex virus 1 (HSV-1) infection on apoptosis of neutrophils from both adults and neonates and present evidence showing that HSV-1 enhances apoptosis in neonatal, but not adult, neutrophils. HSV-1 enhanced the expression of both Fas and Fas ligand on the surface of neonatal neutrophils. Treatments with anti-Fas antibody and a Fas ligand inhibitor significantly reduced the induction of apoptosis by HSV-1. Using an ELISA assay, it was found that HSV-1 infection also leads to increased release of soluble FasL from HSV-1-infected neonatal neutrophils. Increased neonatal neutrophil apoptosis following HSV-1 infection may represent an important mechanism by which HSV-1 may diminish the antiviral response of neonatal neutrophils and might explain, at least in part, the severity of infections that are caused in newborns by this herpesvirus.

Prospective surveillance of Canadian children with the haemolytic uraemic syndrome

We determined prospectively the incidence of childhood diarrhoea associated haemolytic uraemic syndrome (D+ HUS) or HUS due to Streptococcus pneumoniae (SP+ HUS) in Canada through the Canadian Paediatric Surveillance Program (CPSP) network. From April 2000, to March 2002, 82% (1,886/2,300) of all Canadian paediatricians reported possible new cases of D+ HUS or SP+ HUS. Diagnosis was validated with a second questionnaire. There were a total of 136 children with D+ HUS (epidemic, n =15; endemic, n =121), corresponding to an annual incidence rate of 1.11 cases per 100,000 children under 16 years of age. Excluding incomplete forms, the annual incidence rate among endemic cases was 0.74 cases per 100,000. The provinces of Ontario (40%), Quebec (31%), and Alberta (18%) accounted for 89% of cases. Evidence of E. coli O157 or O157:H7 were found in 94% (79/84) of children who had positive stool cultures. The mortality rate was 4% (n =5) and 34% (n =41) of children underwent dialysis for a median of 12 days (2-60 days). SP-HUS was diagnosed in four children with pneumonia and pleural effusion (n =2) or meningitis (n =2) who survived. One child with positive direct Coombs testing had definitive evidence of SP+ HUS. The remaining three were considered possible cases. We conclude that SP+ HUS is rare in Canada. Over the last 15 years, the incidence of childhood D+ HUS in Canadian children may have decreased.

Early Intertwin Differences in Myocardial Performance During the Twin-to-Twin Transfusion Syndrome

Background— In the twin-to-twin transfusion syndrome (TTTS), pressure rather than volume overload is increasingly considered as a key factor in the pathogenesis of the cardiomyopathy of the recipient twin. If this is the case, cardiac dysfunction should be among the first signs observed with TTTS. The objective of this study was to determine whether intertwin differences in myocardial function are modified early in the course of TTTS and whether they can help to differentiate this condition from intrauterine growth restriction (IUGR).

Methods and Results— Eight variables were analyzed on the first fetal echocardiography on 21 pairs of twins with TTTS and 11 with IUGR. No difference was found between the 2 groups for the cardiothoracic ratio, pulsatility indices in the umbilical and middle cerebral arteries, and peak velocity of the middle cerebral artery. Significant difference was found for ventricular septal thickness, but with no association with the conditions under study. With TTTS, left ventricular shortening fraction was consistently greater in the donor twins, and myocardial performance indices (MPIs) were elevated in the recipient twins. This increase in MPI was caused by a lengthening of the isovolumic periods compared with those of the donor twin: left ventricular and right ventricular isovolumic periods 0.105±0.047 and 0.097±0.026 seconds, respectively, for the recipient twins versus 0.0561±0.46 and 0.065±0.03 seconds, respectively, for the donor twins ( P <0.001). These changes in the isovolumic periods were mainly due to significant prolongation of isovolumic relaxation times. A change in left ventricular MPI ≥0.09 combined with a change in right ventricular MPI ≥0.05 would identify a TTTS with a sensitivity of 75% and a false-positive rate of 9%.

Conclusions— The observed diastolic function impairment goes along with the pressure-overload pathogenic concept proposed in TTTS. Assessment of intertwin difference in MPI is a valuable tool for early differential diagnosis between TTTS and isolated IUGR.

Cumulative influence of organ dysfunctions and septic state on mortality of critically ill children

The interaction between sepsis and multiple organ dysfunction syndrome is poorly defined in children. We analyzed by Cox regression models the cumulative influence of organ dysfunctions, using the pediatric logistic organ dysfunction (PELOD) score, and septic state (systemic inflammatory response syndrome or sepsis, severe sepsis, and septic shock) on mortality of critically ill children. We included 593 children (mortality rate: 8.6%) from three pediatric intensive care units; 514 patients had at least a systemic inflammatory response syndrome and 269 had two or more organ dysfunctions. Hazard ratio of death significantly increased with the severity of organ dysfunction, as estimated by the PELOD score, and the worst diagnostic category of septic state. Each increase of one unit in the PELOD score multiplied the hazard ratio by 1.096 (p < 0.0001); hazard ratio of diagnostic category was 9.039 (p = 0.031) for systemic inflammatory response syndrome or sepsis, 18.797 (p = 0.007) for severe sepsis and 32.572 (p < 0.001) for septic shock. Cumulative hazard ratio of death = (hazard ratio of PELOD score) x (hazard ratio of diagnostic category). We conclude that there is a cumulative accrual of the risk of death both with an increasing severity of organ dysfunction and an increasing severity of the diagnostic category of septic state.

Management of fetal tachyarrhythmia based on superior vena cava/aorta Doppler flow recordings

OBJECTIVE

To evaluate a management protocol of fetal supraventricular tachycardia (SVT) based on prior identification of the underlying mechanism.

DESIGN AND SETTING

Prospective study in a mother-child tertiary university centre.

PATIENTS

During a consecutive 36 month period, 18 fetuses with sustained SVT underwent a superior vena cava/ascending aorta (SVC/AA) Doppler investigation in an attempt to determine the atrioventricular (AV) relation and to treat the arrhythmia according to a pre-established management protocol.

MAIN OUTCOME MEASURE

Rate of conversion to sinus rhythm.

RESULTS

Seven fetuses had short ventriculoatrial tachycardia, five of these with a 1:1 AV conduction suggesting re-entrant tachycardia. The first choice drug was digoxin and all were converted. One fetus had AV dissociation leading to the diagnosis of junctional ectopic tachycardia, which was resistant to digoxin and sotalol; amiodarone achieved postnatal conversion. One fetus had SVT and first or second AV block; the diagnosis was atrial ectopic tachycardia (AET), which responded to sotalol given as a drug of first choice. Seven fetuses had long ventriculoatrial tachycardia: one with sinus tachycardia (no treatment), one with permanent junctional reciprocating tachycardia (PJRT), and three with AET. The first choice drug was sotalol and all were converted. One AET was classified postnatally as PJRT. Six fetuses had intra-atrial re-entrant tachycardia: five with 2:1 AV conduction and one with variable block. The first choice drug was digoxin. Conversion was achieved in all but one, who died after birth from advanced cardiomyopathy.

CONCLUSION

The electrophysiological mechanisms of fetal SVT can be clarified with SVC/AA Doppler. The proposed management protocol has so far yielded a good rate of conversion to sinus rhythm.

Ventilator-associated pneumonia in intubated children: comparison of different diagnostic methods

OBJECTIVES

To compare different methods for diagnosis of ventilator-associated pneumonia in intubated children.

DESIGN

Prospective epidemiologic study.

SETTING

Pediatric intensive care unit of a tertiary care university hospital.

PATIENTS

All consecutive pediatric intensive care unit patients <18 yrs of age with suspected ventilator-associated pneumonia.

INTERVENTIONS

For all patients, the following diagnostic methods were compared: 1) clinical data using Centers for Disease Control criteria; 2) blind protected bronchoalveolar lavage, evaluating quantitative cultures, bacterial index of >5, Gram stain, and presence of intracellular bacteria; and 3) nonquantitative cultures of endotracheal secretions. The reference standard used was clinical judgment of three independent experts (Delphi method) who retrospectively established by consensus the presence of ventilator-associated pneumonia based on clinical, microbiological, and radiologic data. Concordance between each diagnostic method and the reference standard was evaluated by concordance percentage and kappa score. Validity was evaluated using sensitivity, specificity, positive predictive value, negative predictive value, and global value.

RESULTS

A total of 30 patients were included in the study. According to the reference standard, ventilator-associated pneumonia occurred in 10 of 30 patients (33%). Bacterial index of >5 in bronchoalveolar secretions showed the best concordance compared with the reference standard (concordance, 83%; kappa, 0.61). Bacterial index of >5 also showed the best validity (sensitivity, 78%; specificity, 86%; positive predictive value, 70%; negative predictive value, 90%; global value, 90%). Intracellular bacteria and Gram stain from bronchoalveolar secretions were very specific (95% and 81%, respectively) but not sensitive (30% and 50%, respectively). Clinical criteria and endotracheal cultures were very sensitive (100% and 90%, respectively) but poorly specific (15% and 40%, respectively).

CONCLUSION

Our data show that the most reliable diagnostic method for ventilator-associated pneumonia is a bacterial index of >5, using blind protected bronchoalveolar lavage. Further studies should evaluate the validity of all these methods according to the gold standard (autopsy).

Mannan-binding lectin in children with Escherichia coli O157:H7 haemmorrhagic colitis and haemolytic uraemic syndrome

Mannan-binding lectin (MBL) triggers complement activation upon binding to microbial surfaces. MBL deficiency has been associated with increased susceptibility to severe bacterial infections. We hypothesized that MBL deficiency may predispose children to Shiga toxin-producing Escherichia coli (STEC) O157:H7 infections and the associated haemolytic uraemic syndrome (HUS). We compared circulating levels of MBL among children with uncomplicated O157:H7 haemorrhagic colitis (HC), patients with O157:H7 HUS, normal and diseases control groups. Circulating MBL concentrations on admission were as follows: 3.22 +/- 2.43 micro g/ml among normal controls (n = 23); 2.90 +/- 2.44 micro g/ml in patients with rotavirus enteritis (n = 10); 2.78 +/- 1.65 micro g/ml in children with HC due to non-STEC bacterial pathogen (n = 15); 2.67 +/- 2.44 micro g/ml in patients with uncomplicated O157:H7 HC (n = 27); 2.80 +/- 2.97 micro g/ml in children with O157:H7 HUS (n = 15); 6.70 +/- 4.49 micro g/ml in patients with chronic renal failure unrelated to O157:H7 infection (n = 6). Higher MBL levels were found in patients with chronic renal failure compared to O157:H7 HC (P < 0.047). However, MBL concentrations <0.5 micro g/ml, which have been associated with MBL deficiency in relation to increased susceptibility to infections, were noted at comparable rates between the different groups (P = NS). Our data does not support that MBL deficiency may predispose to O157:H7 infections nor than the development of diarrhoea associated HUS.

Validation of the paediatric logistic organ dysfunction (PELOD) score: prospective, observational, multicentre study

BACKGROUND

Multiple organ dysfunction syndrome is more frequent than death in paediatric intensive care units. Estimation of the severity of this syndrome could be a useful additional outcome measure in clinical trials in such units. We aimed to validate the paediatric logistic organ dysfunction (PELOD) score and estimate its validity when recorded daily (dPELOD).

METHODS

We did a prospective, observational, multicentre cohort study in seven multidisciplinary, tertiary-care paediatric intensive care units of university-affiliated hospitals (two French, three Canadian, and two Swiss). We included 1806 consecutive patients (median age 24 months; IQR 5-90). PELOD score includes six organ dysfunctions and 12 variables and was recorded daily. For each variable, the most abnormal value each day and during the whole stay were used in calculating the dPELOD and PELOD scores, respectively. Outcome was vital status at discharge. We used Hosmer-Lemeshow goodness-of-fit tests to evaluate calibration and areas under receiver operating characteristic curve (AUC) to estimate discrimination.

FINDINGS

370 (21%) patients had no organ dysfunction, 471 (26%) had one, 457 (25%) had two, and 508 (28%) had three or more. Case fatality rate was 6.4% (115 deaths). PELOD score was significantly higher in non-survivors (mean 31.0 [SE 1.2]) than survivors (9.4 [0.2]; p<0.0001). Calibration (p=0.54) and discrimination (AUC=0.91, SE=0.01) of PELOD and dPELOD (p> or =0.39; AUC> or =0.79) scores were good.

INTERPRETATION

PELOD and dPELOD scores are valid outcome measures of the severity of multiple organ dysfunction syndrome in paediatric intensive care units; their use should significantly reduce the sample size required to complete clinical trials in critically ill children.

Reference values for an index of fetal aortic isthmus blood flow during the second half of pregnancy

OBJECTIVE

During fetal life, the parallel position of the two cardiac ventricles confers a special status to the aortic isthmus. Flow through the isthmus reflects the balance between the performances of the two ventricles and their respective peripheral impedances. This study proposes a fetal aortic isthmus flow velocity index and its reference values defined on the basis of gestational age (GA).

METHODS

Video recordings of 111 normal fetuses from 18 to 39 weeks of gestation were retrospectively reviewed. An isthmus flow velocity index (IFI) was calculated as follows: IFI = (systolic + diastolic)/systolic velocity integrals. GA-specific reference ranges of IFI were constructed.

RESULTS

An IFI of 1.33 +/- 0.03 was found at 18 weeks. This value decreased slightly but steadily with GA to reach 1.23 +/- 0.16 at 39 weeks. This change is mainly related to a decrease in diastolic velocity integrals.

CONCLUSION

The proposed IFI provides information on the direction and, indirectly, on the volume of blood flow through the fetal aortic isthmus.

Changes in flow velocity patterns of the superior and inferior venae cavae during placental circulatory insufficiency

OBJECTIVES

Placental circulatory insufficiency, expressed by the disappearance of the diastolic component of the umbilical artery Doppler velocity waveforms, causes blood flow redistribution that could disturb, to different extents, the systemic venous returns to the heart. The purpose of this study was to investigate the effect of an absence of diastolic blood flow in the umbilical artery on the relationship between the Doppler flow velocities of the venae cavae.

METHODS

Fifteen normal fetuses (normal group) were matched for gestational age with 11 fetuses with absent diastolic flow in the umbilical artery (abnormal group). In the venae cavae, the following Doppler variables were measured and compared between groups: (a) during ventricular systole: maximum (S(max)) and minimum velocities (S(min)) and velocity integrals (SI); (b) during ventricular diastole: peak velocity of the E-wave and its integral (EI), the A-wave and its integral (AI). A venous velocity index (VVI) was defined as (S(max) + S(min))/S(max).

RESULTS

In the normal group, S(min) and VVI were significantly higher in the inferior vena cava (IVC) than in the superior vena cava (SVC). The ratio SVC-VVI/IVC-VVI was therefore always less than one. In the abnormal group, S(min), SI, E, EI and VVI were higher in the SVC compared to those of the IVC. The ratio SVC-VVI/IVC-VVI was always greater than one.

CONCLUSION

In the absence of umbilical artery diastolic flow, a reciprocal shift is observed between the IVC and SVC velocity waveforms characterized by a flow profile in the IVC which resembles that of a normal SVC profile and vice versa. These changes are another manifestation of blood flow redistribution towards the brain in the presence of placental circulatory insufficiency. They should be taken into account on Doppler assessment of ventricular diastolic function based on venous flow patterns during placental circulatory impairment.

Circulating granulocyte colony-stimulating factor, C-X-C, and C-C chemokines in children with Escherichia coli O157:H7 associated hemolytic uremic syndrome

Leukocytes are implicated in the pathogenesis of diarrhea-associated hemolytic uremic syndrome (D(+) HUS). We hypothesized that increased circulating levels of granulocyte colony-stimulating factor (G-CSF), and the chemokines epithelial cell-derived neutrophil-activating protein-78 (ENA-78), growth related oncogen-alpha (GRO-alpha), macrophage inflammatory protein-1beta (MIP-1beta), and monocyte chemotactic protein-1 (MCP-1) are related to the severity of illness in Escherichia coli O157:H7 infections. We compared the circulating concentrations of these mediators in the course of E. coli O157:H7 enteritis, hemorrhagic colitis, and HUS. Our data show that, on admission, children with HUS presented 10-fold abnormally increased levels of G-CSF (p < 0.007), 3-fold increased MIP-1beta concentrations (p < 0.001), and 2-fold lower values of ENA-78 (p < 0.0001). One week later, a further 4-fold decrease in ENA-78 concentration was noted (p < 0.0001) whereas MIP-1beta levels returned to normal. HUS patients requiring peritoneal dialysis showed 6-fold increased G-CSF (p < 0.001) and 5-fold decreased ENA-78 (p < 0.001) levels. On admission, children with uncomplicated O157:H7 hemorrhagic colitis (HC) presented 3-fold abnormally increased concentrations of G-CSF (p < 0.001) and MIP-1beta (p < 0.0001). Those with O157:H7 enteritis but no bloody stools showed higher rates of abnormal GRO-alpha, MIP-1beta, and MCP-1 measurements than children with O157:H7 HC or HUS: GRO-alpha (50% enteritis, 36% HC, 17% HUS; p < 0.06), MIP-1beta (40% enteritis, 22% HC, 11% HUS; p < 0.02), MCP-1 (77% enteritis, 20% HC, 18% HUS; p < 0.0001). The data indicates that GRO-alpha, MIP-1beta, and MCP-1 are produced during E. coli O157:H7 enteritis, whether or not HC or HUS develops. Our data suggest that children with O157:H7 associated HUS may present abnormally increased circulating levels of G-CSF and decreased ENA-78 concentrations. The mechanisms responsible for leukocytes recruitment in O157:H7 infections are unclear and await further studies.

Reproducibility of blind protected bronchoalveolar lavage in mechanically ventilated children

Blind protected bronchoalveolar lavage (BAL) could be an interesting tool in the diagnosis of ventilator-associated pneumonia in intubated children, but its reproducibility has never been evaluated. This study evaluates the reproducibility, feasibility, and safety of blind protected BAL in mechanically ventilated children. Two blind protected BAL were done, at a 2-hour interval, in 30 patients. The reproducibility of microbiologic and cytologic results was studied. A total of 60 BALs was analyzed. Bacterial growth was present in 26 of 60 BAL (43%). Reproducibility for the presence of bacteria on quantitative cultures was excellent (concordance, 93%; kappa [kappa], 0.86). Concordance for the type of bacteria isolated was 86% and for the number of bacteria was 79%. Reproducibility for the presence of neutrophils containing bacteria was perfect (concordance, 100%; kappa, 1) although only a few BALs had a positive result (8/60). Blind protected BAL was feasible in all patients and all samples were considered adequate for analysis. Complications were mostly benign and transitory except in two cases: one pneumothorax and one significant increase in intracranial pressure. Overall, blind protected BAL is a reproducible test in mechanically ventilated children, is easily feasible, and is usually well tolerated.

[Investigation of fetal arrhythmias by simultaneous recording of ascending aortic and superior vena caval blood flow]

In a period of 18 consecutive months, all the foetus referred to our Foetal Cardiology Unit for investigation of arrhythmia were systematically assessed by M mode echocardiography and simultaneous recording of blood flow in the superior vena cava and the aorta (SVC/Ao). This study was undertaken to compare the performance of these two approaches. The foetus were classified into three groups according to the arrhythmia diagnosed: Group 1: irregular arrhythmias, Group 2: bradycardias, Group 3: tachycardias. A surface ECG was recorded in all the neonates in whom the arrhythmias persisted. In Group 1, including 50 cases of extrasystoles (49 atrial and 1 ventricular), M mode echo and the Doppler provided the diagnosis in 42 and 47 cases respectively. This difference was not statistically significant. Group 2 comprised four cases of bradycardia (2 blocked atrial bigeminy, 2 complete atrioventricular blocks); the two methods provided the diagnosis in all 4 cases. Group 3 comprised 11 cases including 7 supraventricular tachycardias (SVT), 2 flutter, 1 chaotic atrial rhythm and 1 ectopic junctional rhythm. Complete analysis of these arrhythmias was possible by M mode in 4 cases and by Doppler in all cases. This difference was significant. The distribution of the 7 cases of SVT with respect to the duration of the ventriculoatrial interval was possible by M mode in 2 cases and in all cases by Doppler. This was a decisive factor in the choice of antiarrhythmic therapy. The authors conclude that Doppler and M mode are two echocardiographic approaches which are equally effective in the investigation of foetal atrial extrasystoles and probably of sustained foetal bradycardia. However, Doppler recording of SVC/Ao gives a more detailed and precise diagnosis of more complex foetal arrhythmias.

Pathogenesis of Shiga toxin-associated hemolytic uremic syndrome

The aim of this review is to examine recent advances in experimental and clinical research relevant to the pathogenesis of diarrhea-associated hemolytic uremic syndrome with special reference to histopathologic findings, virulence factors of Shiga toxin-producing Escherichia coli, the host response, and the prothrombotic state. Despite significant advances during the past decade, the exact mechanism by which Shiga toxin-producing E. coli leads to hemolytic uremic syndrome remains unclear. Factors such as Shiga toxin, lipopolysaccharide, the adhesins intimin and E. coli-secreted proteins A, B, and D, the 60-MD plasmid, and enterohemolysin likely contribute to the pathogenesis. Data on the inflammatory response of the host, including leukocytes and inflammatory mediators, are updated. The pathogenesis of the prothrombotic state leading to thrombocytopenia secondary to endothelial cell damage and platelet activation is also discussed. A hypothetical sequence of events from ingestion of the bacteria to the development of full-blown hemolytic uremic syndrome is proposed.