A Need for a Novel Survival Risk Scoring System for Intensive Care Admissions Due to Sepsis in Pediatric Hematology/Oncology Patients

Background: Children with hemato-oncological diseases or following stem cell transplantation (SCT) are at high risk for life-threatening infections; sepsis in this population constitutes a substantial proportion of pediatric intensive care unit (PICU) admissions. The current pediatric prognostic scoring tools to evaluate illness severity and mortality risk are designed for the general pediatric population and may not be adequate for this vulnerable subpopulation. Methods: Retrospective analysis was performed on all PICU admissions for sepsis in children with hemato-oncological diseases or post-SCT, in a single tertiary pediatric hospital between 2008 and 2021 (n = 233). We collected and analyzed demographic, clinical, and laboratory data and outcomes for all patients, and evaluated the accuracy of two major prognostic scoring tools, the Pediatric Logistic Organ Dysfunction-2 (PELOD-2) and the Pediatric Risk of Mortality III (PRISM III). Furthermore, we created a new risk-assessment model that contains additional parameters uniquely relevant to this population. Results: The survival rate for the cohort was 83%. The predictive accuracies of PELOD-2 and PRISM III, as determined by the area under the curve (AUC), were 83% and 78%, respectively. Nine new parameters were identified as clinically significant: age, SCT, viral infection, fungal infection, central venous line removal, vasoactive inotropic score, bilirubin level, C-reactive protein level, and prolonged neutropenia. Unique scoring systems were established by the integration of these new parameters into the algorithm; the new systems significantly improved their predictive accuracy to 91% (p = 0.01) and 89% (p < 0.001), respectively. Conclusions: The predictive accuracies (AUC) of the PELOD-2 and PRISM III scores are limited in children with hemato-oncological diseases admitted to PICU with sepsis. These results highlight the need to develop a risk-assessment tool adjusted to this special population. Such new scoring should represent their unique characteristics including their degree of immunosuppression and be validated in a large multi-center prospective study.

Safety of Cidofovir Treatment for Suspected or Confirmed Adenovirus Infection in Immunocompetent Pediatric Population

BACKGROUND

Cidofovir (CDV), a nucleoside phosphonate analogue, exhibits activity against severe cytomegalovirus and adenoviral (ADV) infection. Nevertheless, reports of elevated nephrotoxicity rates limited its use to highly vulnerable cases, mainly immunocompromised children with fulminant infection. Limited data exists regarding CDV safety in immunocompetent children.

OBJECTIVE

To evaluate CDV-related toxicity, mainly nephrotoxicity, in immunocompetent children with severe ADV/cytomegalovirus infection.

METHODS

We conducted a retrospective review of medical records for all immunocompetent children under 18 years of age treated with intravenous CDV from January 2005 to December 2019.

RESULTS

Among the 23 patients identified, 21 were diagnosed with severe ADV infection. Median age was 15 months. Twenty-one (91%) children were admitted to the pediatric intensive care unit. Eighteen patients (78%) received standard CDV protocol (5 mg/kg CDV weekly for 2 weeks), 4 (17%) according to nephroprotective low-dose protocol and 1 patient transitioned. The median duration of CDV treatment was 14 days (range: 1-21 days). All patients received hyperhydration and probenecid with each infusion. Acute kidney injury was recorded in 1 patient (with concurrent septic shock) during CDV treatment. Two children exhibited acute kidney injury before CDV initiation, but renal function normalized during CDV treatment. One patient developed transient neutropenia (600 cells/L), apparently as a result of sepsis. No other major adverse effects were noted. Mortality rate was 3/23 (13%), unrelated to CDV toxicity.

CONCLUSIONS

Our findings suggest that CDV-related nephrotoxicity rate in immunocompetent children may be lower than previously reported, perhaps lower than in the severely immunocompromised population.

Therapeutic plasma exchange for neonatal hepatic failure

We report a case of therapeutic plasma exchange in a neonate with fulminant liver failure. A six-day old, 2800-gram baby was referred to our medical center for evaluation and treatment of fulminant hepatic failure. The working diagnosis at admission was gestational alloimmune liver disease, and therapeutic plasma exchange was proposed. A double volume plasma exchange was successfully performed, using the Spectra Optia apheresis system, primed with packed red blood cells. Access was obtained via a radial artery catheter and a peripheral intravenous line. On hospital D-14 a diagnosis of E3 deficiency was confirmed, and disease-specific therapy was started. Automated TPE using peripheral arterial and venous catheters may be safely performed in neonates, and should be considered in the treatment of a variety of disorders including neonatal fulminant hepatic failure.

Acute kidney injury in pediatric toxic shock syndrome is associated with worse clinical course in the intensive care unit

To explore the prevalence, severity, nature, and significance of acute kidney injury (AKI) among children admitted to the pediatric intensive care unit (PICU) with toxic shock syndrome (TSS). Bi-center, retrospective observational study. Children admitted for TSS to two intensive care units from 2009-2022 were included. We identified 41 children (median age 5 years, 46% females) who met the Centers for Disease Control and Prevention (CDC) definitions of TSS. Staphylococcal TSS accounted for 63% of the patients and Streptococcal TSS accounted for the remaining 37%. AKI was diagnosed in 24 (59%) (stage 1: n = 6 [15% of total], stage 2: n = 10 [24%], and stage 3: n = 8 [20%]). The worst creatinine level was measured during the first day of admission in 34 (83%) patients. The median duration of AKI was 2 days. Creatinine normalized by hospital discharge in all cases. Patients with AKI had a longer intensive care unit stay than those without AKI (6 vs. 3 days, respectively, p = 0.01), needed more respiratory support (87% vs. 47%, p = 0.002), had fewer 28 ventilation-free days (25 vs. 28, p = 0.01), fewer vasopressor-free days (25 vs. 28, p = 0.001), and received more blood products (p = 0.03).    Conclusion: Children admitted to the PICU with TSS, show a high prevalence of AKI at presentation. Creatinine levels and clearance normalize by hospital discharge in most cases. AKI in the setting of TSS could be used as an early marker for illness severity and a predictor of a more complex course. What is Known: • TSS is characterized according to the CDC by specific sets of clinical signs and symptoms in conjunction with specific laboratory findings one of which is AKI. • AKI is associated with worse outcomes in critically ill patients in general and in septic patients in particular. What is New: • AKI is found in about 60% of all patients admitted to the PICU with a diagnosis of TSS and hence is an important defining criteria. • AKI in the setting of TSS is associated with a more complex illness course and can serve as an early marker predicting such a course.

Blood pressure monitoring following kidney transplantation in children: a comparison of invasive and noninvasive measurements using Doppler as a benchmark technique

BACKGROUND

Blood pressure (BP) monitoring following pediatric kidney transplantation is essential for optimizing graft perfusion. Differences between invasive BP and noninvasive BP (NIBP) measurements are sometimes considerable. We aimed to assess agreement between invasive BP and NIBP in pediatric patients after kidney transplantation and compare with measurements obtained by systolic Doppler with manual sphygmomanometer as a reference technique.

METHODS

A prospective, observational cohort study, of children aged 18 years or younger, admitted immediately following kidney transplantation to the pediatric intensive care unit of a tertiary, university-affiliated medical center, between May 2019 and June 2021.

RESULTS

Eighty-two paired simultaneous measurements of invasive BP, NIBP, and Doppler BP in 18 patients were compared. Patients were significantly hypertensive, with mean systolic NIBP above the 95th percentile (96 ± 6%). Systolic invasive BP measurements were significantly higher than NIBP (149 ± 20 vs. 136 ± 15 mmHg, p < 0.001). Substantial differences (≥ 20 mmHg) were found in 23% (95% CI 15-34%). Similar disagreement was found between systolic invasive and Doppler BP (150 ± 23 and 137 ± 17 mmHg, respectively, p < 0.001). In contrast, systolic NIBP was in good agreement with Doppler BP (135 ± 17 and 138 ± 18, respectively, p = 0.27). A moderate to strong correlation was found between higher systolic invasive BP and the difference to systolic Doppler BP (Spearman's ρ = 0.63, p < 0.001).

CONCLUSIONS

In children immediately following kidney transplantation, clinically significant disagreement was found between invasive and noninvasive BP measurements. Invasive BP values were significantly higher than those obtained by Doppler. Better agreement was found between NIBP and Doppler. These issues should be considered when interpreting BP measurements in this sensitive patient population. A higher resolution version of the Graphical abstract is available as Supplementary information.

Early post-liver transplant thrombocytopenia in children: Clinical characteristics and significance

BACKGROUND

Post-liver transplant thrombocytopenia is common and associated with worse outcome in adults. In children, however, the prevalence, course, and significance of post-liver transplantation thrombocytopenia are not described. Therefore, we aimed to assess this phenomenon in children.

METHODS

A retrospective chart review of children who underwent liver transplantation at a single tertiary center between 2004 and 2021.

RESULTS

Overall, 130 pediatric liver transplantations were reviewed. During the first 28 POD, thrombocytopenia was evident in 116 (89%, 95% CI 83%-94%). The median nadir platelet count was 54 K/μl (IQR: 37-99). Nadir platelet count was reached in half the patients by the third POD (IQR: 1-6). In multivariate analysis, preoperative platelet count (p = .024), volume of intraoperative packed cell transfusion (p = .045), and hypersplenism (p = .007) were associated with lower postoperative platelet counts. Patients with platelet count lower than the 50th centile on the first POD suffered from a more complicated course leading to a longer PICU admission (p = .039).

CONCLUSIONS

Early post-liver transplant thrombocytopenia appears to be common in children and associated with preoperative thrombocytopenia, hypersplenism, and higher intraoperative blood transfusion volumes. A low first POD platelet count (<86 K/μl) was found to be independently associated with a more complicated postoperative course, suggesting the need for heightened surveillance.

Hyperlactatemia in children following brain tumor resection: prevalence, associated factors, and clinical significance

PURPOSE

Hyperlactatemia is associated with worse outcome among critically ill patients. The prevalence of hyperlactatemia in children following craniotomy for intracranial tumor resection is unknown. This study was designed to assess the prevalence, associated factors, and significance of postoperative hyperlactatemia in this context.

METHODS

A retrospective study was conducted at an intensive care unit of a tertiary, pediatric medical center. Children younger than 18 years admitted following craniotomy for brain tumor resection between October 2004 and November 2019 were included.

RESULTS

Overall, 222 elective craniotomies performed in 178 patients were analyzed. The mean age ± SD was 8.5 ± 5.5 years. All but two patients survived to discharge. All were hemodynamically stable. Early hyperlactatemia, defined as at least one blood lactate level ≥ 2.0 mmol/L during the first 24 h into admission, presented following 74% of the craniotomies; lactate normalized within a mean ± SD of 11 ± 6.1 h. The fluid balance per body weight at 12 h and 24 h into the intensive care unit admission was similar in children with and without hyperlactatemia [7.0 ± 17.6 vs 3.5 ± 16.4 ml/kg, p = 0.23 and 4.0 ± 27.2 vs 4.6 ± 29.4 ml/kg, p = 0.96; respectively]. Hyperlactatemia was associated with higher maximal blood glucose, older age, and a pathological diagnosis of glioma. Intensive care unit length of stay was similar following craniotomies with and without hyperlactatemia (p = 0.57).

CONCLUSIONS

Hyperlactatemia was common in children following craniotomy for brain tumor resection. It was not associated with hemodynamic impairment or with a longer length of stay.

Adenovirus can be a serious, life-threatening disease, even in previously healthy children

AIM

Adenovirus infections are exceedingly common in childhood. However, little is known of the clinical characteristics of children admitted with severe infection to the paediatric intensive care unit (PICU).

METHODS

Clinical data on children hospitalised with adenovirus infection between January 2005 and March 2020 were collected. We compared data between children hospitalised in the PICU and those who were not in a 1:2 ratio.

RESULTS

During the study period, 69 children with adenovirus infection were admitted to the PICU, representing 5% of all hospitalised children with adenovirus. Thirty-four (49%) were previously healthy children. Mortality occurred in 5 patients, and all had an underlying illness. Cidofovir was used in 21 children, including 11 who were previously healthy. No side effects were attributed to the treatment. During 2005-2014, viral co-infection rates were 42% in the PICU group and 11% in the control group (p = 0.002). However, during 2015-2020, when the viral panel became widespread in our institution, the rates of co-infection were similar in the two groups (32% and 34%, p = 1.0).

CONCLUSION

Our findings suggest that adenovirus may present as a serious, life-threatening disease even in previously healthy children.

Intranasal dexmedetomidine vs oral triclofos sodium for sedation of children with autism undergoing electroencephalograms

BACKGROUND

Sedation may be necessary for performing electroencephalograms in children with autistic spectrum disorder, however, our sedation success rate using triclofos sodium (TFS) is limited. Intra-nasal dexmedetomidine (IN-DEX) may be a superior sedative for these children.

OBJECTIVE

Compare IN-DEX with TFS for sedation efficacy, resistance to drug delivery and adverse events in children with autism undergoing an electroencephalogram.

STUDY DESIGN

A single center, prospective observational study of children with autism sedated for electroencephalograms using IN-DEX compared to an age matched, historic group of children with autism, sedated for electroencephalograms using TFS.

RESULTS

Characteristics of 41 IN-DEX sedations were compared to 41 TFS sedations in 82 ASD children. Epileptiform discharges were demonstrated in 23/82 (28%) of children in the cohort. Sedation depth by UMSS was significantly deeper in the IN-DEX group (2.49 ± 0.78 vs. 1.41 ± 0.89, p < 0.001). Electroencephalogram quality demonstrated less motion artifact in the IN-DEX group (1.75 ± 0.76 vs. 2.18 ± 0.88, p < 0.001). The rate of very poor or sedation failure was significantly lower in the IN-DEX group (17% vs 56.1%, p < 0.001), RR = 0.3 (95% CI 0.15 to 0.63, p < 0.001). No major adverse events were documented in either group. Bradycardia occurred in 8/41(19.5%) of children in IN-DEX group and none in TFS group (p = 0.003). Hypotension or poor perfusion were not demonstrated in either group.

CONCLUSION

In children with autism undergoing electroencephalograms, IN-DEX was more tolerable than TFS, induced deeper sedation with a greater success rate, and improved electroencephalogram quality. Both sedatives were equally safe in this population.

Persistent pulmonary air leak in the pediatric intensive care unit: Characteristics and outcomes

BACKGROUND

Persistent air leak (PAL) complicates various lung pathologies in children. The clinical characteristics and outcomes of children hospitalized in the pediatric intensive care unit (PICU) with PAL are not well described. We aimed to elucidate the course of disease among PICU hospitalized children with PAL.

METHODS

A retrospective cohort study of all PICU-admitted children aged 0-18 years diagnosed with pneumothorax complicated by PAL, between January 2005 and February 2020 was conducted at a tertiary center. PAL was defined as a continuous air leak of more than 48 h.

RESULTS

PAL complicated the course of 4.8% (38/788) of children hospitalized in the PICU with pneumothorax. Two were excluded due to missing data. Of 36 children included, PAL was secondary to bacterial pneumonia in 56%, acute respiratory distress syndrome (ARDS) in 31%, lung surgery in 11%, and spontaneous pneumothorax in 3%. Compared to non-ARDS causes, children with ARDS required more drains (median, range: 4, 3-11 vs. 2, 1-7; p < .001) and mechanical ventilation (100% vs. 12%; p < .001), and had a higher mortality (64% vs. 0%; p < .001). All children with bacterial pneumonia survived to discharge, with a median air leak duration of 14 days (range 3-72 days). Most of which (90%) were managed conservatively, by continuous chest drainage.

CONCLUSION

Bacterial pneumonia was the leading cause of PAL in this cohort. PAL secondary to ARDS was associated with a worse outcome. In contrast, non-ARDS PAL was successfully managed conservatively, in most cases.

Ultrasound Cardiac Output Monitor (USCOM™) Measurements Prove Unreliable Compared to Cardiac Magnetic Resonance Imaging in Adolescents with Cardiac Disease

The purpose of this stuy is to prospectively assess the reliability of the ultrasound cardiac output monitor (USCOM™) for measuring stroke volume index and predicting left ventricular outflow tract diameter in adolescents with heart disease. Sixty consecutive adolescents with heart disease attending a tertiary medical center underwent USCOM™ assessment immediately after cardiac magnetic resonance imaging. USCOM™ measured stroke volume index and predicted left ventricular outflow tract diameter were compared to cardiac magnetic resonance imaging-derived values using Bland-Altman analysis. Ten patients with an abnormal left ventricular outflow tract were excluded from the analysis. An adequate USCOM™ signal was obtained in 49/50 patients. Mean stroke volume index was 46.1 ml/m² by the USCOM™ (range 22-66.9 ml/m²) and 42.9 ml/m² by cardiac magnetic resonance imaging (range 24.7-59.9 ml/m²). The bias (mean difference) was 3.2 ml/m²; precision (± 2SD of differences), 17 ml/m²; and mean percentage error, 38%. The mean (± 2SD) left ventricular outflow tract diameter was 0.445 ± 0.536 cm smaller by the USCOM™ algorithm prediction than by cardiac magnetic resonance imaging. Attempted adjustment of USCOM™ stroke volume index using cardiac magnetic resonance imaging left ventricular outflow tract diameter failed to improve agreement between the two modalities (bias 28.4 ml/m², precision 44.1 ml/m², percentage error 77.3%). Our study raises concerns regarding the reliability of USCOM™ for stroke volume index measurement in adolescents with cardiac disease, which did not improve even after adjusting for its inaccurate left ventricular outflow tract diameter prediction.

Routine chest X-ray following ultrasound-guided internal jugular vein catheterization in critically ill children: A prospective observational Study

BACKGROUND

Recent studies in adults have shown that routine chest X-ray following ultrasound-guided central venous catheter insertion through the internal jugular vein is unnecessary due to a low rate of complications.

AIMS

To assess the usefulness of routine chest X-ray following ultrasound-guided central venous catheter insertion through the internal jugular veins in critically ill children.

METHODS

A prospective observational study was conducted at a pediatric intensive care unit of a tertiary, university-affiliated pediatric medical center. All children under the age of 18 who underwent ultrasound-guided central venous catheter insertion through the right or left internal jugular vein between May 2018 and November 2019 were evaluated for eligibility. Procedures were prospectively documented, and chest X-ray was screened for pneumothorax, hemothorax, central venous catheter tip position, and resultant corrective interventions.

RESULTS

Of 105 central venous catheter insertion attempts, 99 central venous catheters (94.3%) were inserted. All were located within the venous system. None were diagnosed with pneumo/hemothorax on chest X-ray. Twenty (20.2%; 95% CI 12.8%-29.5%) were defined as malpositioned by strict criteria; however, only one (1%) was judged significantly misplaced by the clinical team leading to its repositioning.

CONCLUSIONS

In this critically ill pediatric cohort, all central venous catheters inserted under ultrasound guidance could have been used with safety prior to acquiring chest X-ray. Overall chest X-ray impacted patient management in only 1% of cases. Our results do not support delaying urgent central venous catheter use pending chest X-ray completion in critically ill children.

Validation of a computerized scoring system for foreign body aspiration: An observational study

OBJECTIVE

The diagnosis of foreign body aspiration (FBA) is challenging. In a previous study, we developed a computerized scoring system (CSS) to support decision-making. In the present study, we aimed to validate it on a further cohort.

STUDY DESIGN

In this observational study, 100 children referred to the emergency department of a tertiary pediatric hospital for suspected FBA and treated according to standard protocol, were assigned a probability score using the CSS, between 0 and 1 (0, very low probability; 1, very high). The diagnosis of FBA was based on bronchoscopy, and if discharged without bronchoscopy, determined via telephone questionnaire, 4 to 6 months after discharge, supplemented by clinical re-evaluation and bronchoscopy, if respiratory symptoms persisted.

RESULTS

Thirty-five out of 100 children (35%) underwent bronchoscopy with 12 of 35 (34%) positive for FBA. Sixty-five patients were discharged without bronchoscopy and completed a telephone questionnaire. Seven patients required clinical re-evaluation for persistent respiratory symptoms, in two out of them, additional bronchoscopies were performed and were negative. The CSS median probability score was 0.94 in patients with FBA, as compared to 0.73 in patients without FBA (P = .007). The CSS area under the receiver operating curve was 0.74. At a probability score threshold of 0.6, the sensitivity and specificity were 100% and 41%, respectively.

CONCLUSION

The present validation study suggests a high sensitivity of the CSS for the identification of FBA in children. We suggest that it might aid decision-making with regard to the need for bronchoscopy in children presenting to the emergency room.

Hemodynamic effects of intravenous paracetamol in critically ill children with septic shock on inotropic support

Background

Treatment with intravenous paracetamol may impair hemodynamics in critically ill adults. Few data are available in children. The aim of this study was to investigate the frequency, extent, and risk factors of hypotension following intravenous paracetamol administration in children with septic shock on inotropic support.

Methods

We retrospectively reviewed the electronic medical charts of all children aged 1 month to 18 years with septic shock who were treated with intravenous paracetamol while on inotropic support at the critical care unit of a tertiary pediatric medical center in 2013–2018. Data were collected on patient demographics, underlying disease, Pediatric Logistic Organ Dysfunction (PELOD) score, hemodynamic parameters before and up to 120 min after paracetamol administration, and need for inotropic support or intravenous fluid bolus. The main outcome measures were a change in blood pressure, hypotension, and hypotension requiring intervention.

Results

The cohort included 45 children of mean age 8.9 ± 5.1 years. The mean inotropic support score was 12.1 ± 9.5. A total of 105 doses of paracetamol were administered. The lowest mean systolic pressure (108 ± 15 mmHg) was recorded at 60 min (p = 0.002). Systolic blood pressure decreased at 30, 60, 90, and 120 min after delivery of 50, 67, 61, and 59 drug doses, respectively. There were 5 events of systolic hypotension (decrease of 1 to 16 mmHg below systolic blood pressure hypotensive value). Mean arterial pressure decreased by ≥ 15% in 8 drug doses at 30 min (7.6%, mean − 19 ± 4 mmHg), 18 doses at 60 min (17.1%, mean − 20 ± 7 mmHg), 16 doses at 90 min (15.2%, mean − 20 ± 5 mmHg), and 17 doses at 120 min (16.2%, mean − 19 ± 5 mmHg). Mean arterial hypotension occurred at the respective time points in 2, 13, 10, and 9 drug doses. After 12 drug doses (11.4%), patients required an inotropic dose increment or fluid bolus.

Conclusions

Hypotensive events are not uncommon in critically ill children on inotropic support treated with intravenous paracetamol, and physicians should be alert to their occurrence and the need for intervention.

Triclofos Sodium for Pediatric Sedation in Non-Painful Neurodiagnostic Studies

AIM

Triclofos sodium (TFS) has been used for many years in children as a sedative for painless medical procedures. It is physiologically and pharmacologically similar to chloral hydrate, which has been censured for use in children with neurocognitive disorders. The aim of this study was to investigate the safety and efficacy of TFS sedation in a pediatric population with a high rate of neurocognitive disability.

METHODS

The database of the neurodiagnostic institute of a tertiary academic pediatric medical center was retrospectively reviewed for all children who underwent sedation with TFS in 2014. Data were collected on demographics, comorbidities, neurologic symptoms, sedation-related variables, and outcome.

RESULTS

The study population consisted of 869 children (58.2% male) of median age 25 months (range 5-200 months); 364 (41.2%) had neurocognitive diagnoses, mainly seizures/epilepsy, hypotonia, or developmental delay. TFS was used for routine electroencephalography in 486 (53.8%) patients and audiometry in 401 (46.2%). Mean (± SD) dose of TFS was 50.2 ± 4.9 mg/kg. Median time to sedation was 45 min (range 5-245), and median duration of sedation was 35 min (range 5-190). Adequate sedation depth was achieved in 769 cases (88.5%). Rates of sedation-related adverse events were low: apnea, 0; desaturation ≤ 90%, 0.2% (two patients); and emesis, 0.35% (three patients). None of the children had hemodynamic instability or signs of poor perfusion. There was no association between desaturations and the presence of hypotonia or developmental delay.

CONCLUSION

TFS, when administered in a controlled and monitored environment, may be safe for use in children, including those with underlying neurocognitive disorders.

The Hemodynamic Effect of Intravenous Paracetamol in Children: A Retrospective Chart Review

AIM

Studies in adults have reported frequent episodes of blood pressure drops following intravenous paracetamol administration. We aimed to investigate the hemodynamic effects of intravenous paracetamol in critically ill children.

METHODS

The charts of 100 pediatric intensive care patients (age range 0.1-18 years) who were treated with intravenous paracetamol between March and September 2017 were retrospectively reviewed. A hemodynamic event was defined as a drop of > 15% in systolic or mean arterial blood pressure within 120 min after drug administration. Hypotension was defined as either a drop in systolic blood pressure (SBP) below the 5th percentile for age or a hemodynamic event associated with tachycardia, increased lactate level, or treatment with a fluid bolus or vasopressors.

RESULTS

A hemodynamic event was observed in 39 patients (39%). In these patients, SBP was in the pre-hypertension or hypertension values in 36/39 patients before paracetamol administration, median (IQR) SBP decreased from the 99th (95-99) percentile for age before to the 50th (50-95) percentile after paracetamol (p < 0.001) and mean heart rate was 137 bpm before treatment and 115 bpm after (p = 0.002). SBP values did not drop below the 5th percentile in any patient. In 15 patients diagnosed with shock on admission, paracetamol treatment did not cause an increase in vasopressor treatment after drug administration.

CONCLUSIONS

In the present study of critically ill pediatric patients, intravenous paracetamol administration was associated with a drop in SBP from high to normal values for age, possibly due to pain relief, with no evidence for a negative hemodynamic event.

Case Not Closed: Prescription Errors 12 Years after Computerized Physician Order Entry Implementation

OBJECTIVE

To assess the prolonged impact of computerized physician order entry (CPOE) on medication prescription errors in pediatric intensive care patients.

STUDY DESIGN

This observational study was conducted at a pediatric intensive care unit in which a CPOE (Metavision, iMDsoft, Israel) with a limited clinical decision support system was implemented between 2004 and 2007. Since then, no changes were made to the systems. We analyzed 2500 electronic prescriptions (1250 prescriptions from 2015 and 1250 prescriptions from 2016). Prescription errors were identified by a pediatric intensive care physician and classified as potential adverse drug events, medication prescription errors, or rule violations. Their prevalence was compared with the rate in 2007, reported in a previous study from the same unit. A randomly selected 10% of the prescriptions were also analyzed by the pediatric intensive care unit pharmacist, and the level of agreement was determined.

RESULTS

The rate of prescription errors increased from 1.4% in 2007 to 3.2% in 2015 (P = .03). Following revision of the clinical decision support system tools, prescription errors decreased to 1% in 2016 (P < .0001). The potential adverse drug event rate dropped from 2% in 2015 to 0.7% in 2016 (P = .006), and the medication prescription error rate, from 1% to 0.2% (P = .01). The agreement between the 2 reviewers was excellent (k = 0.96).

CONCLUSIONS

The rate of prescription errors may increase with time from implementation of a CPOE. Repeated surveillance of prescription errors is highly advised to plan strategies to reduce them. This approach should be considered in quality improvement of computerized information systems in general.

Pulmonary hypertension specific treatment in infants with bronchopulmonary dysplasia

OBJECTIVE

When bronchopulmonary dysplasia (BPD) is complicated by pulmonary hypertension (PH), morbidity and mortality are significantly increased. BPD-associated PH is not included in the current indications for PH medications. However, limited data demonstrate hemodynamic improvement and decreased mortality with PH-specific treatment. This report describes our 6-year experience treating BPD-associated PH with PH medications, mainly sildenafil.

STUDY DESIGN

The medical records of 20 infants diagnosed with BPD-associated PH at a tertiary pediatric pulmonary hypertension clinic in 2008-2014 were reviewed. Clinical improvement was defined as a decrease in Ross functional class by at least one degree. PH severity was classified by echocardiography as mild, moderate, or severe. Hemodynamic improvement was defined as a decrease in PH severity by at least one level.

RESULTS

Eighteen out of 20 patients were treated with PH medications: 12 sildenafil, 5 sildenafil and bosentan, and 1 bosentan. Median follow-up time was 2 years. Mean functional class significantly decreased from 3.2 ± 0.9 at diagnosis to 1.7 ± 0.9 at the last follow-up. Improvement in functional class was observed in 15/16 children (94%). Moderate or severe PH was found in 13/18 children (72%) at diagnosis, and in three (17%, all moderate PH) at the last follow-up. Improvement in PH class by echocardiography was demonstrated in 14/18 children (78%). The survival rate was 95%.

CONCLUSION

Treatment of BPD complicated by PH with PH-specific medications, mainly sildenafil, is associated with improvement in both clinical and hemodynamic parameters and a low mortality rate. Pediatr Pulmonol. 2017;52:77-83. © 2016 Wiley Periodicals, Inc.

Validation of a pediatric obstructive sleep apnea screening tool

OBJECTIVE

Pediatric obstructive sleep apnea (OSA) is a prevalent but under-diagnosed disease. The importance of screening for OSA in every child has been recently re-emphasized by the American Academy of Pediatrics Guidelines. Although several screening questionnaires are available for pediatric OSA, they are either complicated to use or not sensitive enough, and therefore OSA is seldom screened in primary care settings. Here, we validated a previously developed short (6-item) hierarchically-based screening questionnaire tool for pediatric OSA.

METHODS

Parents of 85 children referred for a sleep study at a pediatric community-based sleep clinic completed the questionnaire and their children underwent an overnight PSG. Receiver operator curve analyses and other predictive scales were assessed.

RESULTS

The 6-item questionnaire exhibited favorable sensitivity and fair specificity for diagnosis of OSA, which varied depending on the apnea-hypopnea index used for OSA definition.

CONCLUSIONS

A 6-item questionnaire is a sensitive and easy-to-use screening tool for pediatric OSA in a pediatric sleep clinic setting.

Polymerase-chain-reaction-based diagnosis of viral pulmonary infections in immunocompromised children

Aim

Viral pneumonia is a serious complication in immunocompromised children. Its aetiology is difficult to identify owing to the limitations of conventional microbiological tests. The aim of this study was to determine whether polymerase chain reaction (PCR) assays for respiratory viruses increase the diagnostic yield of bronchoalveolar lavage (BAL) in immunocompromised children.

Methods

BAL samples obtained from immunocompromised children hospitalized with pneumonia were processed for respiratory viruses by viral culture, rapid antigen test and PCR (for CMV, adenovirus, influenza, parainfluenza, herpesvirus, RSV and hMPV).

Results

The study group included 42 patients (mean age 7.2 ± 5.1 years) with 50 episodes of clinical pneumonia (50 BAL samples). Forty viral pathogens were identified in 30 episodes (60%). PCR increased the diagnostic rate by fourfold (75% identified by PCR alone, p < 0.0001). When viral culture and rapid antigen test were used as the gold standard, PCR was found to have high sensitivity (86–100% when assessed) and specificity (80–96%). The PCR results prompted the initiation of specific antiviral therapy and the avoidance of unnecessary antibiotic treatment in 17 (34%) episodes.

Conclusion

PCR‐based diagnosis from BAL may increase the rate of pathogen detection in immunocompromised children, decrease the time to diagnosis and spare patients unnecessary antimicrobial treatment.

Desmoid tumour biology in patients with familial adenomatous polyposis coli

BACKGROUND

Familial adenomatous polyposis (FAP) is caused by mutations in the adenomatous polyposis coli (APC) gene. Desmoid tumours affect up to 26 per cent of patients and contribute significantly to death. This study aimed to assess the influence of sex and mutation site on desmoid tumour development and sex-specific genetic differences in patients with FAP with and without desmoid tumours.

METHODS

Patients with FAP-associated desmoid tumours recorded in the Heidelberg Polyposis Register between 1991 and 2010 were identified. These patients were analysed with respect to clinical parameters and possible risk factors.

RESULTS

Some 105 patients with FAP-associated desmoid tumours of a total of 585 patients with FAP were analysed. Male patients had a significantly greater number of desmoid tumours and a larger tumour mass, although tumours were more common in female patients. Desmoid tumours in male patients were located more often in the abdominal wall. Seventy-nine (75.2 per cent) of the 105 patients demonstrated a clear temporal association between a previous operation and subsequent desmoid tumour development; most of these patients were female. Mutation sites in male patients were limited to exons 5, 14 and 15, whereas female patients carried mutations along the entire coding region of the APC gene. Twenty-one per cent of patients with desmoid tumours carried mutations within the 'desmoid region', compared with only 4.1 per cent of the control group without desmoids.

CONCLUSION

There are significant sex differences concerning desmoid tumour manifestation. Female patients appear to have a higher risk of desmoid tumour occurrence independent of the mutation site, whereas in male patients the mutation site seems to exert more influence.

Polymerase-chain-reaction-based diagnosis of invasive fungal pulmonary infections in immunocompromised children

OBJECTIVE

Fungal pneumonia is a serious complication in immunocompromised children. It is difficult to diagnose because of the low sensitivity of clinical and standard laboratory tests. The aim of this study was to investigate the diagnostic impact of polymerase chain reaction (PCR) assays for fungal pathogens in bronchoalveolar lavage (BAL) fluid.

STUDY DESIGN

BAL samples obtained from hospitalized immunocompromised patients with clinical pneumonia between January 2007 and June 2009 were processed for microscopy and cultures in addition to PCR-based fungal assays. The results were compared between the standard and PCR methods.

RESULTS

Seventy-seven children with 100 episodes of pneumonia were included in the study. Fungal pathogens were detected by standard microbiological investigations in 10 episodes (10%) and by PCR-based assays alone in 20 episodes (20%). There was no significant difference in clinical improvement or mortality rate between patients diagnosed by the different methods. In 61 episodes, no fungal pathogen was identified by either method. Prolonged antifungal therapy was avoided in 43 episodes.

CONCLUSION

PCR-based assay for the diagnosis of fungal pulmonary infections may be a useful adjunct to clinical and standard microbiological techniques. The use of PCR may decrease the time to diagnosis, increase the rate of detection of fungal pathogens, and spare patients unnecessary antifungal treatment.

Nitric oxide for post-liver-transplantation hypoxemia in pediatric hepatopulmonary syndrome: case report and review

HPS is rare in the pediatric population. Liver transplantation is the ultimate treatment for severe HPS. There are only a few case reports and one series of children in whom HPS was the main indication for liver transplantation. Outcome was good in most of them, with full regression of the pulmonary process. However, hypoxemia in the early post-operative course can have severe consequences, and effective treatment modalities are needed. There are rare instances of the use of iNO for the treatment of post-operative hypoxemia. We describe a 10.5-yr-old boy with severe HPS owing to chronic liver disease after bone marrow transplantation. Liver transplantation from a living related donor (the same sister who donated the bone marrow) was complicated by severe hypoxemia on POD 2. iNO was administered via the ventilator circuit and, after extubation, through nasal prongs. It was slowly tapered down and stopped on POD 10. The child had an otherwise uneventful course and was discharged home on POD 21 with normal oxygen saturation. Liver transplantation should be offered to children with severe HPS. iNO can reverse the hypoxemia that may occur after the operation.

Postoperative thrombotic thrombocytopenic purpura in an infant: case report and literature review

Thrombotic thrombocytopenic purpura is caused by an imbalance of von Willebrand factor and its cleaving protease, which leads to the formation of microthrombi in end-organs. It rarely occurs in the pediatric population. Plasma exchange can significantly reduce mortality and morbidity. We present a 14-month-old infant in whom clinical and laboratory abnormalities compatible with thrombotic thrombocytopenic purpura were noted several days after resection of a large pelvic tumor. Treatment with double volume plasma exchange on postoperative day 5 led to complete resolution of the renal failure, thrombocytopenia, anemia, and neurological manifestations. ADAMTS13 inhibitors were negative and no mutations were found in factor H, factor I, membrane cofactor protein, and thrombomodulin to account for genetic predisposition to thrombotic thrombocytopenic purpura or atypical hemolytic uremic syndrome. Postoperative anemia, thrombocytopenia, fever, and neurological deficits in children should raise the suspicion of thrombotic thrombocytopenic purpura. Early diagnosis is important because the disorder is readily and efficiently treated with plasma exchange.

Central apnoeas in infants with bronchiolitis admitted to the paediatric intensive care unit

AIM

To further characterize apnoea(s) complicating bronchiolitis because of respiratory syncytial virus (RSV), to describe the incidence of this complication and identify possible risk factors for apnoea(s) and its development.

METHODS

The files of infants admitted to the paediatric intensive care unit (PICU) for RSV bronchiolitis during three bronchiolitis seasons (2004-2007) were reviewed for demographic, clinical and laboratory parameters. Parameters were compared between patients with and without apnoeas.

RESULTS

Seventy-nine patients met the study criteria: 43 were admitted to the PICU for central apnoeas and the remainder for respiratory distress or failure. The percentage of infants admitted for apnoea increased during the study period (28.6 to 77.1%, p = 0.004). The overall prevalence of apnoea in this population was 4.3%. Possible risk factors for apnoea(s) were younger age (1.3 vs. 4.3 months, p = 0.002), lower admission weight (3.3 vs. 5 kg, p < 0.001), lower gestational age (35.8 vs. 37.8 weeks, p = 0.01), admission from the emergency room (50% vs. 9.1%, p < 0.001) and lack of hyperthermia (p < 0.001). Respiratory acidosis was found to be a protective factor on logistic regression analysis.

CONCLUSION

The prevalence of apnoea in infants admitted to the PICU for RSV bronchiolitis in our centre may be increasing. Preterm, younger infants with no fever are at relatively high risk of apnoea at presentation, while older infants with fever are at lower risk.

Bi-Level Positive Airway Pressure Ventilation in Pediatric Oncology Patients With Acute Respiratory Failure

The aim of the study was to describe our experience with bi-level positive airway pressure (BiPAP) ventilation in oncology children with acute respiratory failure, hospitalized in a single tertiary pediatric tertiary center. This was a retrospective cohort study of all pediatric oncology patients in our center admitted to the intensive care unit with acute hypoxemic or hypercarbic respiratory failure from January 1999 through May 2006, who required mechanical ventilation with BiPAP. Fourteen patients met the inclusion criteria with a total of 16 events of respiratory failure or impending failure: 12 events were hypoxemic, 1 was combined hypercarbic and hypoxemic, and 3 had severe respiratory distress. Shortly after BiPAP ventilation initiation, there was a statistically significant improvement in the respiratory rate (40.4 ± 9.3 to 32.5 ± 10.1, P < .05] and a trend toward improvement in arterial partial pressure of oxygen (PaO 2; 71.3 ± 32.7 to 104.6 ± 45.6, P = .055). The improvement in the respiratory status was sustained for at least 12 hours. In 12 (75%) events there was a need for sedation during ventilation; 12 children needed inotropic support during the BiPAP ventilation. Bi-level positive airway pressure ventilation failed in 3 (21%) children who were switched to conventional ventilation. All of them have died during the following days. One child was recategorized to receive palliative care while on BiPAP ventilator and was not intubated. In 12 of 16 BiPAP interventions (75%; 11 patients), the children survived to pediatric intensive care unit (PICU) discharge without invasive ventilation. No major complications were noted during BiPAP ventilation. Bi-level positive airway pressure ventilation is well tolerated in pediatric oncology patients suffering from acute respiratory failure and may offer noninferior outcomes compared with those previously described for conventional invasive ventilation. It appears to be a feasible initial option in children with malignancy experiencing acute respiratory failure.

Computerized order entry with limited decision support to prevent prescription errors in a PICU

OBJECTIVE

The value of computerized physician order entry (CPOE) and clinical decision support systems (CDSSs) in preventing prescription errors in pediatrics is unclear. We investigated the change in prescription error rates with the introduction of CPOE with and without a CDSS limited to weight-based dosing in a PICU.

METHODS

In a PICU of a major tertiary-care pediatric medical center, 5000 orders were reviewed, that is, 1250 orders from each of 4 periods: period 1, before CPOE implementation; period 2, 1 year after CPOE implementation; period 3, after CDSS implementation; and period 4, after a change in prescription authorization. Prescription errors were identified and classified into: potential adverse drug events (ADEs), medication prescription errors (MPEs), and rule violations (RVs).

RESULTS

We identified 273 errors (5.5%). The rate of potential ADEs decreased slightly between periods 1 and 2 (from 2.5% to 2.4%) and significantly in periods 3 and 4 (to 0.8% and 0.7%, respectively; P < .005). The rate of MPEs decreased slightly between periods 1 and 2 (from 5.5% to 5.3%), but new types of MPEs appeared. There was a significant decrease in period 3 (to 3.8%; P < .05) and a dramatically significant decrease in period 4 (to 0.7%; P < .0005). Only 3 RVs were found. Interrater agreement (kappa statistic) was 0.788 between evaluators.

CONCLUSIONS

CPOE implementation decreased prescription errors only to a small extent. However, the addition of a CDSS that limits doses by weight significantly reduced prescription error rates and, most importantly, potential ADEs. This finding emphasizes the major impact of weight-based calculation errors in pediatrics.

Computerized Scoring System for the Diagnosis of Foreign Body Aspiration in Children

Objectives:

Foreign body aspiration (FBA) is a life-threatening event in children. The gold standard for diagnosis is bronchoscopy, but there is no consensus regarding indications for the procedure. The aim of this study was to formulate a predictive model for assessing the probability of FBA in suspected cases as an aid in the decision to perform diagnostic bronchoscopy.

Methods:

The files of 150 patients who underwent bronchoscopy for suspected FBA at our center between 1996 and 2004 were reviewed for medical history, physical examination, and radiologic studies. The findings were analyzed by logistic regression.

Results:

Using the file data, we formulated a predictive model wherein each parameter received a numeric coefficient representing its significance in evaluating suspected FBA. The most significant parameters were age 10 to 24 months, foreign body in the child's mouth and severe respiratory complaints during the choking episode, hypoxemia, dyspnea or stridor following the acute event, unilateral signs on lung auscultation, abnormal tracheal radiogram, unilateral infiltrate or atelectasis, and local hyperinflation or obstructive emphysema on chest radiogram.

Conclusions:

In our predictive model, every case of suspected FBA can be assigned a score based on the specific parameters present, which is then entered into a probability formula to determine the likelihood of a positive diagnosis. This model may serve as a useful tool for deciding on the use of bronchoscopy in all children with suspected FBA.

L1 makes immunological progress by expanding its relations

The cell-adhesion molecule L1 was originally described in the nervous system. It has recently been detected in CD4+ T lymphocytes, peripheral B lymphocytes, and granulocytes in the human immune system and in similar leucocyte types in the murine immune system. L1 mediates neural recognition by Ca+2, Mg+2-independent homophilic binding. In the human and murine immune systems, L1 binds to the "classical" vitronectin receptor, alphaVbeta3, and fibronectin receptor, alpha5beta1, respectively, and abstains from homophilic binding. Homophilic L1 binding probably involves antiparallel alignment of several interactive domains. Integrin binding is mediated by a short segment of immunoglobulinlike domain 6, which includes two RGD repeats in rodent L1 and one RGD motif in human L1. L1 is modulated in activated leucocytes in vitro in parallel to L-selectin, and diverse cell types release intact L1 in vivo and in vitro. Released L1 can bind to laminin and adheres to the extracellular matrix of sciatic nerve, M21 melanoma, and possibly spleen and other tissues. It can support integrin-dependent cell migration and preliminary data implicate it in tumor development and transnodal lymphocyte migration.

The cell adhesion molecule L1: species- and cell-type-dependent multiple binding mechanisms

The cell adhesion molecule L1 is known to mediate neuronal adhesion, neurite fasciculation, and stimulation of fibroblastin growth factor (FGF)-receptor-dependent neurite outgrowth by homophilic interaction. Recent findings have also revealed heterophilic interactions between L1 and two "classical" integrin matrix receptors, murine alpha 5 beta 1 and human alpha V beta 3. The homophilic binding mechanism of L1 involves multiple domains and has been conserved in chicken neuron-glia cell adhesion molecule (NgCAM) and mammalian L1. The integrin-binding site of L1 contains the tripeptide Arg-Gly-Asp but varies among different species. L1-integrin binding predominates in leucocyte subsets and in several tumours. It can mediate homotypic and heterotypic cell-cell adhesion and haptotactic cell movement on substrate-embedded L1. L1 is released in response to cytokines by at least some neuronal and leucocyte types. It can be detected in the extracellular matrix and conceivably contributes to cell and axonal navigation. Antibody perturbation studies indicate that the integrin-binding site of L1 is important for granule cell migration and neurite outgrowth in postnatal murine cerebellum, possibly via modulation of the src signal transduction pathway. The model of L1 binding seems to be governed by the cell, but it does not correlate with known alternative splicing or glycosylation patterns of L1.

Adhesive hierarchy involving the cell adhesion molecules L1, CD24, and alpha 6 integrin in murine neuroblastoma N2A cells

The aggregation rate of resuspended neuroblastoma N2A cells depends on the density of the cells in culture prior to their resuspension: isolated, fast growing cells have a weak tendency to aggregate whereas confluent, slowly growing cells reaggregate very strongly. L1 antibody 557 strongly inhibited the slow aggregation of isolated, fast growing cells but not the reaggregation of confluent cells. CD24 (nectadrin) antibodies did not affect the aggregation of isolated or confluent cells but stimulated the aggregation of subconfluent cells. In all stages aggregation was not inhibited when antibody 557 was used together with CD24 antibodies at 37 degrees C in the presence of divalent cations. EA-1 antibody to alpha 6 integrin chain stimulated the aggregation of subconfluent cells but inhibited the reaggregation of confluent cells. Therefore, L1 appears to be an early recognition molecule mediating weak primary adhesion. CD24 appears to participate in activating secondary adhesion mechanisms during primary adhesion, possibly in cooperation with L1, and alpha 6 integrin seems to serve as a secondary, strong adhesion molecule that in early adhesion phases also mediates the activation of itself or of other adhesion mechanisms. These results indicate that neural cells might employ a strategy of adhesion cascade in establishing stable contacts.

Evidence for cis interaction and cooperative signalling by the heat-stable antigen nectadrin (murine CD24) and the cell adhesion molecule L1 in neurons

L1 is a transmembranal homophilic cell adhesion molecule of the immunoglobulin superfamily expressed by neural and lymphoid cells. The heat-stable antigen (HSA, murine CD24) nectadrin is a highly and heterogeneously glycosylated glycophosphatidylinositol-linked differentiation antigen of haematopoietic and neural cells. L1 and nectadrin have been shown to mediate cell adhesion and intracellular Ca2+ signals in neurons and B lymphoblasts, respectively. Here we show that nectadrin is co-expressed with L1 in murine cerebellar granule cell neurons and neuroblastoma N2A cells. Purified nectadrin bound to L1 with an apparent binding ratio of five nectadrin molecules to one L1 molecule at saturation. Binding between nectadrin and purified N-CAM was not observed. In co-capping experiments nectadrin co-redistributed with L1 and N-CAM. Since in these cells N-CAM and L1 cohere by cis-binding nectadrin appears to join the L1-N-CAM complex through binding to L1. Antibodies to each L1 and nectadrin evoked small increases in the intracellular Ca2+ concentration. However, when both antibodies were added together or in tandem to the cells, a strong intracellular Ca2+ signal was measured that was at least 6- and 10-fold stronger than the signal separately induced by L1 and nectadrin antibodies respectively. Such a cooperative effect was not observed in B lymphoblasts, using the same antibodies, or in neurons, using a combination of L1 and Thy-1 antibodies. Both the weak Ca2+ signal mediated by L1 alone and the enhanced signal jointly triggered by antibodies to L1 and nectadrin were inhibited by phorbol 12-myristate 13-acetate and were not significantly affected by Ni2+ and Cd2+ cations, suggesting that they are related to one another and involve recruitment of intracellular Ca2+. Nectadrin therefore appears to join a functional complex of neuronal adhesion molecules and to potentiate the signal transduction pathway of L1, possibly in response to neuron-neuron contact formation.

Differential, LFA-1-sensitive effects of antibodies to nectadrin, the heat-stable antigen, on B lymphoblast aggregation and signal transduction

Nectadrin, the heat-stable antigen (HSA), is a highly glycosylated GPI-linked glycoprotein that can undergo homophilic and heterophilic binding. In the present work we have examined short-term effects of nectadrin antibodies on splenic B lymphoblast aggregation and signal transduction. Monoclonal antibody 79 inhibited cell aggregation and induced an intracellular Ca++ signal in the absence of cross-linking. Both these effects were perturbed in the presence of LFA-1 antibodies. Nectadrin antibody M1/69 and polyclonal nectadrin antibodies stimulated cell aggregation, did not induce a Ca++ signal, and their effects were functionally independent of LFA-1. These results suggest that nectadrin may concomitantly mediate primary and activate secondary adhesion mechanisms whereby each of these processes may be related to a different signal transduction pathway.

Expression of L1 cell adhesion molecule is associated with lymphoma growth and metastasis

The cell adhesion molecule (CAM) L1 is involved in homotypic and heterotypic adhesion between neural cells. It has recently also been identified on leucocytes. We have investigated the expression of L1 on hematopoietic tumor cell lines and found that several tumors including the ESb-MP lymphoma are positive for L1. A potential role for L1 in spontaneous metastasis formation was examined using these cells. From wild-type (wt) L1high lymphoma cells we selected by a fluorescence-activated cell sorter (FACS) stable L1low expression variants. Syngeneic DBA/2 mice injected subcutaneously with L1low clones showed faster primary tumor growth, developed visceral metastases significantly faster and died earlier than animals carrying L1high wt cells. L1 high revertants from the L1low variants showed again a reduced metastatic capacity and a malignancy similar to the wt cells. Expression of L1 on the tumor variants and revertants correlated directly with their homotypic aggregation behaviour in vitro. L1 expression correlated negatively with metastatic capacity. These results suggest that L1 molecules may contribute to the overall malignant potential of the lymphoma cells, presumably by interfering with cell-cell interactions critical for tumor growth and dissemination.

Nectadrin, the heat-stable antigen, is a cell adhesion molecule

Nectadrin, the cell surface glycoprotein recognized by the novel mAb 79, was found to be immunologically identical to the heat-stable antigen (HSA). It is a glycoprotein with a polypeptide core of only 30 amino acids and a very high carbohydrate content (Wenger, R. H., M. Ayane, R. Bose, G. Köhler, and P. J. Nielsen. 1991. Eur. J. Immunol. 21:1039-1046). Immunocytological studies using cultured splenic B-lymphocytes, neuroblastoma cells, and cerebellar cells indicated that nectadrin is preferentially expressed at sites of cell-cell contact. Purified nectadrin and monoclonal nectadrin antibody 79, but not other monoclonal nectadrin antibodies, inhibited the aggregation of B-lymphocytes by 70%, suggesting that nectadrin may act as a cell adhesion molecule. Nectadrin was purified from a mouse lymphoma cell line in two forms of 40-60 and 23-30 kD. The lower molecular weight form appears to be generated from the higher molecular weight form by degradative removal of saccharide residues characteristic of complex type oligosaccharide side chains. Latex beads coated with purified nectadrin aggregated and the rate of their aggregation depended on the molecular form of nectadrin, with the larger form being more potent than the smaller one in mediating bead aggregation. Nectadrin thus appears to be a self-binding cell adhesion molecule of a structurally novel type in that its extensive glycan structures may be implicated in mediating cell adhesion.

Expression and function of the neural cell adhesion molecule L1 in mouse leukocytes

The neural cell adhesion molecule L1 is a cell surface glycoprotein of the immunoglobulin superfamily which mediates adhesion between neural cells. The possibility that similar cell-cell recognition mechanisms may be shared by the nervous and immune systems prompted us to study the expression and function of L1 in cells of the hematopoietic system. Immunofluorescence analysis using monoclonal L1 antibody revealed that the molecule is expressed in the bone marrow, spleen, and thymus of the mouse. This observation was confirmed by amplifying cDNA derived from these organs by the polymerase chain reaction with L1-specific oligonucleotide primers. Two-color fluorescence analysis indicated that bone marrow lymphoid and granulocyte precursor cells express low and high levels of L1, respectively. In the thymus L1 is primarily expressed by mature cells that have a strong expression of CD3 and in the spleen both B cells and T cells express L1. The possible function of L1 in lymphoid cells was studied using subcloned ESb-MP lymphoma cells having high or low densities of L1 on the cell surface as well as activated splenic B lymphoblasts. Parental and subcloned ESb-MP cells that strongly expressed L1 could form homotypic aggregates in the presence of low Ca2+ levels, whereas subcloned ESb-MP cells with a weak expression of L1 did not aggregate, suggesting that L1 mediates the Ca(2+)-independent aggregation of the parental ESb-MP cells. Furthermore, the aggregation of activated B lymphoblasts under physiological concentrations of Ca2+ and Mg2+ was inhibited by 30% in the presence of Fab fragments of polyclonal L1 antibodies, implying that L1 also mediates adhesion among normal lymphoid cells. A possible role of L1 on lymphocytes in stimulating the innervation of lymphoid organs is discussed.

Retention of J1/tenascin and the polysialylated form of the neural cell adhesion molecule (N-CAM) in the adult olfactory bulb

To gain insight into the cellular and molecular mechanisms underlying neurogenesis in adult mouse olfactory bulb, several adhesion molecules expressed by glial cells and neurons were investigated. In the germinal zone of the olfactory bulb, the subependymal layer of the rostral region of the lateral ventricles, two adhesion molecules are detectable that are characteristic of early morphogenetic events: J1/tenascin and the polysialylated form, the so-called embryonic form, of N-CAM. The polysialylated form of N-CAM is expressed by most cells in the subependymal layer, and by some astrocytes and neurons in the granular layer adjacent to the subependymal layer. This suggests that bipotential precursor cells retain expression of the embryonic form during their migration from the subependymal layer and during the first stages of differentiation into neurons and glia. Expression of the polysialylated form of N-CAM is also retained in monolayer cultures of six-day-old olfactory bulbs, 55 days after seeding in vitro. J1/tenascin was detectable in the subependymal layer using two monoclonal antibodies. The immunostaining pattern was different between the two antibodies and more restricted to the subependymal layer than when staining with polyclonal J1 antibodies was performed, indicating that J1/tenascin exists in distinct isoforms. Finally, our observations suggest that, in the adult olfactory bulb, L1 is not only a neuron-neuron adhesion molecule, but it may also be involved in neuron-glia interactions, since it is found at contact sites between these two cell types. L1, therefore, may be a neuron-glia adhesion molecule in some parts of the CNS, while it is not in others.

The neural cell adhesion molecule N-CAM enhances L1-dependent cell-cell interactions

On neural cells, the cell adhesion molecule L1 is generally found coexpressed with N-CAM. The two molecules have been suggested, but not directly shown, to affect each other's function. To investigate the possible functional relationship between the two molecules, we have characterized the adhesive interactions between the purified molecules and between cultured cells expressing them. Latex beads were coated with purified L1 and found to aggregate slowly. N-CAM-coated beads did not aggregate, but did so after addition of heparin. Beads coated with both L1 and N-CAM aggregated better than L1-coated beads. Strongest aggregation was achieved when L1-coated beads were incubated together with beads carrying both L1 and N-CAM. In a binding assay, the complex of L1 and N-CAM bound strongly to immobilized L1, but not to the cell adhesion molecules J1 or myelin-associated glycoprotein. N-CAM alone did not bind to these glycoproteins. Cerebellar neurones adhered to and sent out processes on L1 immobilized on nitrocellulose. N-CAM was less effective as substrate. Neurones interacted most efficiently with the immobilized complex of L1 and N-CAM. They adhered to this complex even when its concentration was at least 10 times lower than the lowest concentration of L1 found to promote adhesion. The complex became adhesive for cells only when the two glycoproteins were preincubated together for approximately 30 min before their immobilization on nitrocellulose. The adhesive properties between cells that express L1 only or both L1 and N-CAM were also studied. ESb-MP cells, which are L1-positive, but N-CAM negative, aggregated slowly under low Ca2+. Their aggregation could be completely inhibited by antibodies to L1 and enhanced by addition of soluble N-CAM to the cells before aggregation. N2A cells, which are L1 and N-CAM positive aggregated well under low Ca2+. Their aggregation was partially inhibited by either L1 or N-CAM antibodies and almost completely by the combination of both antibodies. N2A and ESb-MP cells coaggregated rapidly and their interaction was similarly inhibited by L1 and N-CAM antibodies. These results indicate that L1 is involved in two types of binding mechanisms. In one type, L1 serves as its own receptor with slow binding kinetics. In the other, L1 is modulated in the presence of N-CAM on one cell (cis-binding) to form a more potent receptor complex for L1 on another cell (trans-binding).

Functional cooperation between the neural adhesion molecules L1 and N-CAM is carbohydrate dependent

The neural cell adhesion molecules L1 and N-CAM have been suggested to interact functionally by formation of a complex between the two molecules (Kadmon, G., A. Kowitz, P. Altevogt, and M. Schachner. 1990. J. Cell Biol. 110:193-208). To determine the molecular mechanisms underlying this functional cooperation, we have studied the contribution of carbohydrates to the association of the two molecules at the cell surface. Aggregation or adhesion between L1- and N-CAM-positive neuroblastoma N2A cells was reduced when the synthesis of complex and/or hybrid glycans was modified by castanospermine. Fab fragments of polyclonal antibodies to L1 inhibited aggregation and adhesion of castanospermine-treated cells almost completely, whereas untreated cells were inhibited by approximately 50%. Fab fragments of polyclonal antibodies to N-CAM did not interfere with the interaction between castanospermine-treated cells, whereas they inhibited aggregation or adhesion of untreated cells by approximately 50%. These findings indicate that cell interactions depending both on L1 and N-CAM ("assisted homophilic" binding) can be reduced to an L1-dominated interaction ("homophilic binding"). Treatment of cells with the carbohydrate synthesis inhibitor swainsonine did not modify cell aggregation in the absence or presence of antibodies compared with untreated cells, indicating that castanospermine-sensitive, but swainsonine-insensitive glycans are involved. To investigate whether the appropriate carbohydrate composition is required for an association of L1 and N-CAM in the surface membrane (cis-interaction) or between L1 on one side and L1 and N-CAM on the other side of interacting partner cells (trans-interaction), an L1-positive lymphoid tumor cell line was coaggregated with and adhered to neuroblastoma cells in the various combinations of castanospermine-treated and untreated cells. The results show that it is the cis-interaction between L1 and N-CAM that depends on the appropriate carbohydrate structures.

Expression of L1 and N-CAM cell adhesion molecules during development of the mouse olfactory system

The expression of the neural adhesion molecules L1 and N-CAM has been studied in the embryonic and early postnatal olfactory system of the mouse in order to gain insight into the function of these molecules during development of a neural structure which retains neuronal turnover capacities throughout adulthood. N-CAM was slightly expressed and L1 was not significantly expressed in the olfactory placode on Embryonic Day 9, the earliest stage tested. Rather, N-CAM was strongly expressed in the mesenchyme underlying the olfactory placode. In the developing nasal pit, L1 and N-CAM were detectable in the developing olfactory epithelium, but not in regions developing into the respiratory epithelium. At early developmental stages, expression of the so-called embryonic form of N-CAM (E-N-CAM) coincides with the expression of N-CAM, whereas at later developmental stages and in the adult it is restricted to a smaller number of sensory cell bodies and axons, suggesting that the less adhesive embryonic form is characteristic of morphogenetically dynamic neuronal structures. Moreover, E-N-CAM is highly expressed at contact sites between olfactory axons and their target cells in the glomeruli of the olfactory bulb. L1 and N-CAM 180, the component of N-CAM that accumulates at cell contacts by interaction with the cytoskeleton are detectable as early as the first axons extend toward the primordial olfactory bulb. L1 remains prominent throughout development on axonal processes, both at contacts with other axons and with ensheathing cells. Contrary to N-CAM 180 which remains detectable on differentiating sensory neuronal cell bodies, L1 is only transiently expressed on these and is no longer detectable on primary olfactory neuronal cell bodies in the adult. Furthermore, whereas throughout development L1 has a molecular form similar to that seen in other parts of the developing and adult central nervous systems, N-CAM and, in particular, N-CAM 180 retain their highly sialylated form at least partially throughout all ages studied. These observations suggest that E-N-CAM and N-CAM 180 are characteristic of developmentally active structures and L1 may not only be involved in neurite outgrowth, but also in stabilization of contacts among fasciculating axons and between axons and ensheathing cells, as it has previously been found in the developing peripheral nervous system.

Expression of cell adhesion molecules in the olfactory system of the adult mouse: presence of the embryonic form of N-CAM

The expression of the neural cell adhesion molecules N-CAM and L1 was investigated in the olfactory system of the mouse using immunocytochemical and immunochemical techniques. In the olfactory epithelium, globose basal cells and olfactory neurons were stained by the polyclonal N-CAM antibody reacting with all three components of N-CAM (N-CAM total) in their adult and embryonic states. Dark basal cells and supporting cells were not found positive for N-CAM total. The embryonic form of N-CAM (E-N-CAM) was only observed on the majority of globose basal cells, the precursor cells of olfactory neurons, and some neuronal elements, probably immature neurons, since they were localized adjacent to the basal cell layer. Differentiated neurons in the olfactory epithelium did not express E-N-CAM. In contrast to N-CAM total, the 180-kDa component of N-CAM (N-CAM180) and E-N-CAM, L1 was not detectable on cell bodies in the olfactory epithelium. L1 and N-CAM180 were strongly expressed on axons leaving the olfactory epithelium. Olfactory axons were also labeled by antibodies to N-CAM180 and L1 in the lamina propria and the nerve fiber and glomerular layers of the olfactory bulb, but only some axons showed a positive immunoreaction for E-N-CAM. Ensheathing cells in the olfactory nerve were observed to bear some labeling for N-CAM total, L1, and N-CAM180, but not E-N-CAM. In the olfactory bulb, L1 was not present on glial cells. In contrast, N-CAM180 was detectable on some glia and N-CAM total on virtually all glia. Glia in the nerve fiber layer were labeled by E-N-CAM antibody only at the external glial limiting membrane. In the glomerular layer, E-N-CAM expression was particularly pronounced at contacts between olfactory axons and target cells. The presence of E-N-CAM in the adult olfactory epithelium and bulb was confirmed by Western blot analysis. The continued presence of E-N-CAM in adulthood on neuronal precursor cells, a subpopulation of olfactory axons, glial cells at the glia limitans, and contacts between olfactory axons and their target cells indicates the retention of embryonic features in the mammalian olfactory system, which may underlie its remarkable regenerative capacity.