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OBJECTIVES To describe coronavirus disease 2019 (COVID-19)–related pediatric hospitalizations during a period of B.1.617.2 (Δ) variant predominance and to determine age-specific factors associated with severe illness. METHODS We abstracted data from medical charts to conduct a cross-sectional study of patients aged RESULTS Of 947 hospitalized patients, 759 (80.1%) had COVID-19, of whom 287 (37.8%) had severe illness. Factors associated with severe illness included coinfection with respiratory syncytial virus (RSV) (PR 3.64) and bacteria (PR 1.88) in infants; RSV coinfection in patients aged 1 to 4 years (PR 1.96); and obesity in patients aged 5 to 11 (PR 2.20) and 12 to 17 years (PR 2.48). Having ≥2 underlying medical conditions was associated with severe illness in patients aged CONCLUSIONS Among patients hospitalized for COVID-19, factors associated with severe illness included RSV coinfection in those aged

Acute chest syndrome (ACS) is a common and serious lung complication in sickle cell disease. A retrospective medical chart review was performed over a 6-year period in all pediatric ACS patients to investigate whether factors during the initial hospitalization were associated with recurrent ACS episodes. There were 386 episodes of ACS: 149 had only 1 episode of ACS, and 76 had > 1 episode of ACS; 172 (76.4%) had hemoglobin SS, and 39 (17.3%) had hemoglobin SC. The most common presenting features were fever (83%), pain (70%), and cough (61%), which changed with the number of ACS episodes. Children < 4 years old were at greatest risk of recurrent ACS (P = 0.018). In addition, history of asthma (adjusted incident rate ratio [IRR] = 1.52; 95% confidence interval [CI], 1.22–1.98; P < 0.0001), shortness of breath (IRR, 1.29; 95% CI, 1.02–1.62; P = 0.033), and length of hospital stay (IRR, 1.04; 95% CI, 1.01–1.08; P = 0.017) were significantly associated with prospective ACS events. Multiple episodes of ACS are common in sickle cell disease, and certain risk factors during the initial hospitalization are associated with recurrent ACS.

Background Interferon-induced transmembrane protein 3 (IFITM3) restricts endocytic fusion of influenza virus. IFITM3 rs12252_C, a putative alternate splice site, has been associated with influenza severity in adults. IFITM3 has not been evaluated in pediatric influenza. Methods The Pediatric Influenza (PICFLU) study enrolled children with suspected influenza infection across 38 pediatric intensive care units during November 2008 to April 2016. IFITM3 was sequenced in patients and parents were genotyped for specific variants for family-based association testing. rs12252 was genotyped in 54 African-American pediatric outpatients with influenza (FLU09), included in the population-based comparisons with 1000 genomes. Splice site analysis of rs12252_C was performed using PICFLU and FLU09 patient RNA. Results In PICFLU, 358 children had influenza infection. We identified 22 rs12252_C homozygotes in 185 white non-Hispanic children. rs12252_C was not associated with influenza infection in population or family-based analyses. We did not identify the Δ21 IFITM3 isoform in RNAseq data. The rs12252 genotype was not associated with IFITM3 expression levels, nor with critical illness severity. No novel rare IFITM3 functional variants were identified. Conclusions rs12252 was not associated with susceptibility to influenza-related critical illness in children or with critical illness severity. Our data also do not support it being a splice site.

Few educational opportunities exist in paediatric cardiac critical care units (PCCUs). We introduced a new educational activity in the PCCU in the form of of patient-specific summaries (TPSS). Our objective was to study the role of TPSS in the provision of a positive learning experience to the multidisciplinary clinical team of PCCUs and in improving patient-related clinical outcomes in the PCCU.Prospective educational intervention with simultaneous clinical assessment was undertaken in PCCU in an academic children's hospital. TPSS was developed utilizing the case presentation format for upcoming week's surgical cases and delivered once every week to each PCCU clinical team member. Role of TPSS to provide clinical education was assessed using five-point Likert-style scale responses in an anonymous survey 1 year after TPSS provision. Paediatric cardiac surgery patients admitted to the PCCU were evaluated for postoperative outcomes for TPSS provision period of 1 year and compared with a preintervention period of 1 year.TPSS was delivered to 259 clinical team members including faculty, fellows, residents, nurse practitioners, nurses, respiratory therapists and others from the Divisions of Anesthesia, Cardiology, Cardio-Thoracic Surgery, Critical Care, and Pediatrics working in the PCCU. Two hundred and twenty-four (86%) members responded to the survey and assessed the role of TPSS in providing clinical education to be excellent based on mean Likert-style scores of 4.32 ± 0.71 in survey responses. Seven hundred patients were studied for the two time periods and there were no differences in patient demographics, complexity of cardiac defect and surgical details. The length of mechanical ventilation for the TPSS period (57.08 ± 141.44 h) was significantly less when compared with preintervention period (117.39 ± 433.81 h) (P0.001) with no differences in length of PCICU stay, hospital stay and mortality for the two time periods.Provision of TPSS in a paediatric cardiac surgery unit is perceived to be beneficial in providing clinical education to multidisciplinary clinical teams and may be associated with improved clinical outcome.

Background: Acute lower respiratory tract illness is a major cause of hospitalization, respiratory failure, and death in children worldwide. However, infectious agents are not identified in >50% of these clinical illnesses using traditional methods such as rapid antigen detection assays or viral culture. Objective: To conduct a pilot study using RT-PCR to determine the frequency of respiratory viruses in critically ill children with respiratory compromise. Methods: Critically ill children admitted to the Pediatric Critical Care Unit during 2 winter seasons with respiratory compromise or failure were prospectively enrolled. Respiratory tract specimens (tracheal lavage or nasal wash) were tested for 11 different viruses using realtime RT-PCR, including respiratory syncytial virus (RSV), human metapneumovirus (HMPV), influenza A (IAV) and B (IBV), parainfluenza viruses (PIV) 1-3, coronaviruses OC43, 229E, and Netherlands, and human rhinovirus (HRV). Results: Thirty-two children were enrolled, 28 (88%) of which required mechanical ventilation. Clinical diagnoses included bronchiolitis, croup, asthma, apnea, and pneumonia. Of these patients, 28/32 (88%) tested positive for one of eleven viruses by RT-PCR. Compared to antigen testing for RSV, IAV, and IBV, RT-PCR detected an additional nine infections for an increased yield of 53%. RT-PCR also detected coronavirus infections in five patients, including three patients with Netherlands coronavirus. Co-infection with more than one virus was detected in 8/32 (25%). None of the 32 patients tested positive for HMPV, PIV 1, or PIV 3. Conclusions: We detected a respiratory virus in 88% of children with respiratory failure. RT-PCR significantly increased the identification of viruses compared to antigen testing. RSV, influenza A, and coronaviruses were the most common viruses detected. Our data suggest that a viral etiology can be identified in the majority of childhood episodes of severe respiratory disease and that RT-PCR is a useful addition to the diagnostic approach.

Septic shock heterogeneity has important implications for clinical trial implementation and patient management. We previously addressed this heterogeneity by identifying three putative subclasses of children with septic shock based exclusively on a 100-gene expression signature. Here we attempted to prospectively validate the existence of these gene expression-based subclasses in a validation cohort.Prospective observational study involving microarray-based bioinformatics.Multiple pediatric intensive care units in the United States.Separate derivation (n = 98) and validation (n = 82) cohorts of children with septic shock.None other than standard care.Gene expression mosaics of the 100 class-defining genes were generated for 82 individual patients in the validation cohort. Using computer-based image analysis, patients were classified into one of three subclasses ("A," "B," or "C") based on color and pattern similarity relative to reference mosaics generated from the original derivation cohort. After subclassification, the clinical database was mined for phenotyping. Subclass A patients had higher illness severity relative to subclasses B and C as measured by maximal organ failure, fewer intensive care unit-free days, and a higher Pediatric Risk of Mortality score. Patients in subclass A were characterized by repression of genes corresponding to adaptive immunity and glucocorticoid receptor signaling. Separate subclass assignments were conducted by 21 individual clinicians using visual inspection. The consensus classification of the clinicians had modest agreement with the computer algorithm.We have validated the existence of subclasses of children with septic shock based on a biologically relevant, 100-gene expression signature. The subclasses have relevant clinical differences.

To determine the incidence and clinical and biomarker predictors of perioperative thrombosis in children with single ventricle physiology undergoing staged palliation.Nineteen patients were enrolled and 16 completed the study. Serial ultrasounds of the central venous system were performed to evaluate for thrombus. Plasma antithrombin III, thrombin-antithrombin complex, protein C, protein S, tissue factor pathway inhibitor, plasminogen activator inhibitor-1, tissue plasminogen activator antigen, D-dimer, soluble CD40 ligand, and urinary thromboxane were measured serially before and after surgery. Cardiopulmonary bypass time, aortic cross clamp time, blood product administration, inotrope score, chest tube output, cardiac function by echocardiography, intensive care unit and hospital lengths of stay, and central venous catheter days were recorded.The incidence of perioperative thrombus was 31%. Patients who developed a thrombus had poorer preoperative ventricular function (p = 0.03) and longer cardiopulmonary bypass times (p = 0.03) than those who did not develop a thrombus. Preoperative plasma antithrombin III was lower (p = 0.01) and tissue plasminogen activator antigen concentrations were higher (p = 0.02) in patients with a thrombus compared with patients without a thrombus. When measured over time, antithrombin III remained lower (p = 0.002) and tissue plasminogen activator antigen higher (p = 0.005) in those who developed a thrombus compared with those who did not. There were no other statistically significant differences in biomarkers of coagulation between patients with and without thrombosis.One-third of patients undergoing palliative surgery for single ventricle physiology develop thrombosis. Decreased ventricular function, low antithrombin III, and increased tissue plasminogen activator may predict those most suitable for randomized clinical trials of anticoagulation.

To validate a diagnostic instrument for pediatric delirium in critically ill children, both ventilated and nonventilated, that uses standardized, developmentally appropriate measurements.A prospective observational cohort study investigating the Pediatric Confusion Assessment Method for Intensive Care Unit (pCAM-ICU) patients in the pediatric medical, surgical, and cardiac intensive care unit of a university-based medical center.A total of 68 pediatric critically ill patients, at least 5 years of age, were enrolled from July 1, 2008, to March 30, 2009.None.Criterion validity including sensitivity and specificity and interrater reliability were determined using daily delirium assessments with the pCAM-ICU by two critical care clinicians compared with delirium diagnosis by pediatric psychiatrists using Diagnostic and Statistical Manual, 4th Edition, Text Revision criteria.A total of 146 paired assessments were completed among 68 enrolled patients with a mean age of 12.2 yrs. Compared with the reference standard for diagnosing delirium, the pCAM-ICU demonstrated a sensitivity of 83% (95% confidence interval, 66-93%), a specificity of 99% (95% confidence interval, 95-100%), and a high interrater reliability (κ = 0.96; 95% confidence interval, 0.74-1.0).The pCAM-ICU is a highly valid reliable instrument for the diagnosis of pediatric delirium in critically ill children chronologically and developmentally at least 5 yrs of age. Use of the pCAM-ICU may expedite diagnosis and consultation with neuropsychiatry specialists for treatment of pediatric delirium. In addition, the pCAM-ICU may provide a means for delirium monitoring in future epidemiologic and interventional studies in critically ill children.

Delirium is a syndrome of acute brain dysfunction that commonly occurs in critically ill adults and most certainly is prevalent in critically ill children all over the world. The dearth of information about the incidence, prevalence, and severity of pediatric delirium stems from the simple fact that there have not been well-validated instruments for routine delirium diagnosis at the bedside. This article reviewed the emerging solutions to this problem, including description of a new pediatric tool called the pCAM-ICU. In adults, delirium is responsible for significant increases in both morbidity and mortality in critically ill patients. The advent of new tools for use in critically ill children will allow the epidemiology of this form of acute brain dysfunction to be studied adequately, will allow clinical management algorithms to be developed and implemented following testing, and will present the necessary incorporation of delirium as an outcome measure for future clinical trials in pediatric critical care medicine.

The urea cycle and nitric oxide cycle play significant roles in complex biochemical and physiologic reactions. These cycles have distinct biochemical goals including the clearance of waste nitrogen; the production of the intermediates ornithine, citrulline, and arginine for the urea cycle; and the production of nitric oxide for the nitric oxide pathway. Despite their disparate functions, the two pathways share two enzymes, argininosuccinic acid synthase and argininosuccinic acid lyase, and a transporter, citrin. Studying the gene expression of these enzymes is paramount in understanding these complex biochemical pathways. Here, we examine the expression of genes involved in the urea cycle and the nitric oxide cycle in a panel of eleven different tissue samples obtained from individual adults without known inborn errors of metabolism. In this study, the pattern of co-expressed enzymes provides a global view of the metabolic activity of the urea and nitric oxide cycles in human tissues. Our results show that these transcripts are differentially expressed in different tissues. Using the co-expression profiles, we discovered that the combination of expression of enzyme transcripts as detected in our study, might serve to fulfill specific physiologic function(s) including urea production/nitrogen removal, arginine/citrulline production, nitric oxide production, and ornithine production. Our study reveals the importance of studying not only the expression profile of an enzyme of interest, but also studying the expression profiles of the other enzymes involved in a particular pathway so as to better understand the context of expression. The tissue patterns we observed highlight the variety of important functions of these enzymes and provides insight into the many clinical observations that result from their disruption. These results have implications for the management of urea cycle patients and raise considerations for the care of those patients receiving liver transplants. Finally, this work reaffirms the concept that the co-expression of a few genes can significantly impact complex biochemical and physiologic processes.

Objective Pulmonary hypertension may complicate surgical correction of congenital heart defects, resulting in increased morbidity and mortality. We have previously shown that plasma levels of the nitric oxide precursors citrulline and arginine drop precipitously after congenital cardiac surgery and that oral citrulline supplementation may be protective against the development of pulmonary hypertension. In this study, we assessed the safety and pharmacokinetic profile of intravenous citrulline as a potential therapy for postoperative pulmonary hypertension. Methods The initial phase of this investigation was a dose-escalation study of intravenously administered citrulline in infants and children undergoing one of five congenital cardiac surgical procedures (phase 1). The primary safety outcome was a 20% drop in mean arterial blood pressure from the baseline pressure recorded after admission to the intensive care unit. Based on our previous work, the target circulating plasma citrulline trough was 80 to 100 μmol/L. Each patient was given two separate doses of citrulline: the first in the operating room immediately after initiation of cardiopulmonary bypass and the second 4 hours later in the pediatric intensive care unit. Stepwise dose escalations included 50 mg/kg, 100 mg/kg, and 150 mg/kg. After model-dependent pharmacokinetic analysis, we enrolled an additional 9 patients (phase 2) in an optimized dosing protocol that replaced the postoperative dose with a continuous infusion of citrulline at 9 mg/(kg·h) for 48 hours postoperatively. Results The initial stepwise escalation protocol (phase 1) revealed that an intravenous citrulline dose of 150 mg/kg given after initiation of cardiopulmonary bypass yielded a trough level of in the target range of approximately 80 to 100 μmol/L 4 hours later. The postoperative dose revealed that the clearance of intravenously administered citrulline was 0.6 L/(h·kg), with a volume of distribution of 0.9 L/kg and estimated half-life of 60 minutes. Because of the short half-life, we altered the protocol to replace the postoperative dose with a continuous infusion of 9 mg/(kg·h). An additional 9 patients were studied with this continuous infusion protocol (phase 2). Mean plasma citrulline levels were maintained at approximately 125 μmol/L, with a calculated clearance of 0.52 L/(h·kg). None of the 17 patients studied had a 20% drop in mean arterial blood pressure from baseline. Conclusions In this first report of the use of intravenous citrulline in humans, we found citrulline to be both safe and well tolerated in infants and young children undergoing congenital cardiac surgery. Because of the rapid clearance, the optimal dosing regimen was identified as an initial bolus of 150 mg/kg given at the initiation of cardiopulmonary bypass, followed 4 hours later by a postoperative infusion of 9 mg/(kg·h) continued up to 48 hours. Using this regimen, plasma arginine, citrulline, and nitric oxide metabolite levels were well maintained. Intravenous citrulline needs to be studied further as a potential therapy for postoperative pulmonary hypertension.

The objective of this study was to determine whether the implementation of an inhaled nitric oxide protocol (INO) in a pediatric ICU (PICU) would reduce cost associated with its use without negatively affecting patient outcomes.This is a retrospective cohort study of 76 subjects who required INO therapy in the PICU during the study period. A nitric oxide setup and weaning protocol was implemented in the PICU. The medical records of subjects who had received INO 18 months after protocol implementation, as well as the medical records of subjects who had received INO in the 18 months before protocol implementation, were reviewed. Length of time on INO, cost of INO per subject, mortality, stay, and ventilator hours were recorded.There were 38 subjects in the pre-protocol group and 38 subjects in the post-protocol group. There was a statistically significant decrease in the median per subject cost of INO between the pre- and post-protocol groups (P.01). There was no statistically significant difference in the median duration of INO use (P = .06), median PICU (P = .42) or hospital (P = .58) stay, median duration of mechanical ventilation (P = .79) or percent mortality (P = .28) between the 2 groups.Implementation of an INO setup and weaning protocol in a PICU reduces the cost associated with its use without a statistically significant difference in mortality. In an era of increased awareness regarding healthcare spending, implementation of evidence-based protocols can provide a way to ensure the judicious utilization of medical resources.

CPSI deficiency is an inborn error of metabolism caused by mutations in the first, rate-determining enzyme of the urea cycle. Our mutation detection data from this disorder suggest that a significant number of mutant alleles cause RNA instability, most likely through the nonsense-mediated decay pathway. We identified 26 non-consanguinous CPSID patients with an available RNA source (liver tissue or cell line) and screened both genomic DNA and RNA for the identification and classification of mutations. Out of 52 total alleles screened from these patients, 21 (40%) have strong evidence for RNA processing mutations demonstrated by absent/minimal heterozygosity in patient cDNA sequences despite heterozygous genomic changes. These 21 alleles are a heterogenous group primarily composed of splicing defects and frameshifts that form premature termination codons which should subsequently elicit the nonsense-mediated decay pathway. This study provides evidence for the high prevalence of RNA instability mutations in genetic disease and underscores the importance of accounting for them in mutation-screening strategies.

Purpose This paper describes the methodology of a clinical trial of prone positioning in pediatric patients with acute lung injury (ALI). Nonrandomized studies suggest that prone positioning improves oxygenation in patients with ALI/acute respiratory distress syndrome without the risk of serious iatrogenic injury. It is not known if these improvements in oxygenation result in improvements in clinical outcomes. A clinical trial was needed to answer this question. Materials and Methods The pediatric prone study is a multicenter, randomized, noncrossover, controlled clinical trial. The trial is designed to test the hypothesis that at the end of 28 days, children with ALI treated with prone positioning will have more ventilator-free days than children treated with supine positioning. Secondary end points include the time to recovery of lung injury, organ failure–free days, functional outcome, adverse events, and mortality from all causes. Pediatric patients, 42 weeks postconceptual age to 18 years of age, are enrolled within 48 hours of meeting ALI criteria. Patients randomized to the prone group are positioned prone within 4 hours of randomization and remain prone for 20 hours each day during the acute phase of their illness for a maximum of 7 days. Both groups are managed according to ventilator protocol, extubation readiness testing, and sedation protocols and hemodynamic, nutrition, and skin care guidelines. Conclusions This paper describes the process, multidisciplinary input, and procedures used to support the design of the clinical trial, as well as the challenges faced by the clinical scientists during the conduct of the clinical trial.

Most often, urea cycle disorders have been described as acute onset hyperammonemia in the newborn period; however, there is a growing awareness that urea cycle disorders can present at almost any age, frequently in the critical care setting. This article presents three cases of adult-onset hyperammonemia caused by inherited defects in nitrogen processing in the urea cycle, and reviews the diagnosis, management, and pathophysiology of adult-onset urea cycle disorders. Individuals who have milder molecular urea cycle defects can lead a relatively normal life until a severe environmental stress triggers a hyperammonemic crisis. Comorbid conditions such as physical trauma often delay the diagnosis of the urea cycle defect. Prompt recognition and treatment are essential in determining the outcome of these patients.

Objective. Medication errors are a major concern of health care professionals and medical institutions, especially errors involving children. Studies in adults have shown that computerized physician order entry (CPOE) systems reduce medication errors and adverse drug events (ADEs). The effect of CPOE implementation in a pediatric population has not been reported. The objective of this study was to evaluate the impact of CPOE on the frequency of errors in the medication ordering process in a pediatric critical care unit (PCCU). Methods. A prospective trial was conducted of 514 pediatric patients who were admitted to a 20-bed PCCU in a tertiary-care children’s hospital before and after implementation of CPOE. Medication errors were identified after review of all orders during the study period and then further classified as potential ADEs, medication prescribing errors (MPE), and rule violations (RV). Results. A total of 13 828 medication orders were reviewed. Before implementation, potential ADEs occurred at a rate of 2.2 per 100 orders, MPEs at a rate of 30.1 per 100 orders, and RVs at a rate of 6.8 per 100 orders. After implementation, the rate of potential ADEs was reduced to 1.3 per 100 orders, MPEs to 0.2 per 100 orders, and RVs to 0.1 per 100 orders. The overall error reduction was 95.9%. Potential ADEs were reduced by 40.9%, and MPEs and RVs were reduced by 99.4% and 97.9%, respectively. Conclusions. The implementation of CPOE resulted in almost a complete elimination of MPEs and RVs and a significant but less dramatic effect on potential ADEs.

Objective. The deaths of 4 infants who had confirmed pertussis infection at our hospital during the past year motivated us to review their cases as well as the use of extracorporeal membrane oxygenation (ECMO) in respiratory failure caused by pertussis.Methods. Retrospective chart reviews of the 4 infants who had pertussis and died at Vanderbilt University Medical Center (VUMC) from May 2001 to May 2002 were conducted. The Extracorporeal Life Support Organization (ELSO) database is an international voluntary registry established in 1986 to compile passive reports of adult and pediatric patients placed on ECMO. We searched this database for pertussis cases and analyzed the clinical outcomes by age, ventilatory management, and measurements of cardiopulmonary status.Results. All 4 infants who died from pertussis infection at VUMC were younger than 3 months and had severe pulmonary hypertension, and ECMO therapy was considered for respiratory failure. Review of the international ELSO database, focusing only on children from 1986 to July 2002, revealed a total of 23 970 patients placed on ECMO. Since the first pertussis case treated with ECMO in 1990, a total of 61 children with pertussis have been treated with ECMO, representing an increase from 0.09% to 1% of the total cases. Mean age of the pertussis patients placed on ECMO was 88 days (1 day–2.7 years). The overall mortality was 70.5% (43 of 61) but was significantly higher for infants who were younger than 6 weeks (84%) compared with infants who were older than 6 weeks (61%). When evaluating pre-ECMO management, survivors had received significantly higher mean positive end expiratory pressures than nonsurvivors (11.1 ± 4.5 vs 7.3 ± 3.1 cmH2O) and had significantly higher serum pH than nonsurvivors (7.31 ± 0.14 vs 7.14 ± 0.19). There was no effect of duration of ECMO, positive inspiratory pressure, mean arterial pressure, ECMO mode (venoarterial vs venovenous mode), or sex on mortality.Conclusions. Although the ECMO registry is not an active surveillance system, it suggests that the numbers of children who require ECMO for pertussis have significantly increased. The high fatality rates of pertussis patients who have placed on ECMO are alarming and should stimulate reevaluation of whether this high-risk intervention is beneficial to patients with pertussis. This review, coupled with the 4 infants who died of pertussis at VUMC, suggests that improved measures are needed to prevent pertussis in infants.

Other than relapse, pulmonary complications are the most common cause of mortality in patients who undergo bone marrow transplantation (BMT). Diffuse alveolar hemorrhage (DAH) is one noninfectious pulmonary complication of BMT. Presenting clinical findings include nonproductive cough usually without hemoptysis, dyspnea, hypoxemia, a decrease in hematocrit, and diffuse infiltrates on chest radiograph.We report a case of DAH after allogeneic BMT in a 6-yr-old female patient. Although a chest radiograph revealed patchy bilateral alveolar densities and large volumes of bright red blood were suctioned from the endotracheal tube, there was no evidence of coagulopathy and no infectious agent was identified on examination of bronchoalveolar lavage fluid, blood, and urine.The child was treated with high-dose corticosteroids and high-frequency oscillatory ventilation and experienced a complete clinical recovery from her pulmonary disease.The definition, presenting symptoms, findings and timing, and associated risk factors of DAH after BMT are reviewed. Prospective hypotheses for the pathogenesis of DAH after BMT are presented. Evidence for the role of high-dose corticosteroids for treatment of DAH after BMT and the role of high-frequency oscillatory ventilation for treatment of acute hypoxemic respiratory failure in children with diffuse alveolar disease is also reviewed.This case supports the contention that early treatment with high-dose corticosteroids is warranted in children with DAH after BMT.

In the alveolar lumen, pulmonary surfactant converts from the contents of secreted lamellar bodies to tubular myelin to apoprotein-depleted vesicles during respiration. Using an in vitro system, researchers have reported that the conversion of tubular myelin to vesicles is blocked by inhibitors of serine hydrolase activity and have tentatively ascribed “convertase” activity to a diisopropyl fluorophosphate (DFP)-binding protein in mouse bronchoalveolar lavage (BAL). We purified and sequenced the homologous enzyme from rat BAL fluid. Amino acid sequence from the amino terminus and an internal cyanogen bromide peptide of the purified rat DFP-binding protein perfectly match the sequence of the carboxylesterase ES-2. Although ES-2 was initially cloned from liver, we found a 1.8-kilobase mRNA for ES-2 in decreasing relative abundance in rat liver, kidney, and lung but not in heart or spleen. Although further studies are required to establish the identity between “convertase” and ES-2 or a homologous member of the carboxylesterase family, our results raise the possibility that a protein with esterase/lipase activity plays a role in extracellular surfactant metabolism.

Much of current knowledge and momentum in the field of pulmonary hypertension (PH) has not penetrated the increasingly heterogeneous pediatric population managed by pediatric subspecialists worldwide. It is critical to prospectively test specific agents in children. Yet, the broad spectrum of pediatric pulmonary vascular diseases and the lack of clinically meaningful end points appropriate for the pediatric population pose challenges for the conduct of sufficiently powered pediatric studies. It is therefore no surprise that in the midst of significant advances in the field, there are no agents approved for use in children afflicted with PH with the exception of inhaled nitric oxide (iNO) for infants with persistent PH of the newborn (PPHN). The current and widely accepted WHO framework by which pediatric subspecialists are guided is not easily translated into the expanding range of situations encountered in pediatric practice. Like PPHN, it may be necessary to approach these pediatric pulmonary hypertensive conditions from outside the frameworks proposed for typical adult-onset diseases. Exploration of the potential intrinsic differences between children and adults may yield important discoveries regarding the genesis of disease in children and adults alike Fortunately, most children with PH are seen within specialized pediatric centers where there are untapped opportunities for multicenter collaboration. Our aim in this chapter is to approach pediatric PH over the age and development continuum from the vantage point of the pediatric subspecialists who encounter these patients in practice. We will review the abnormalities of pulmonary vascular tone and structure that impact the health and survival of children currently cared for in pediatric PH centers. Many of these disease processes occur commonly from our vantage point, yet are underrepresented in the broader field of PH research or current classification schemes. We will also address the challenges that pediatric subspecialists face in defining PH and assessing its severity in infants or children across the developmental and disease spectrums.

The introduction of inhaled nitric oxide (iNO) for the treatment of hypoxemic respiratory failure in neonates ushered in a new era in neonatal intensive care. This inhalational therapeutic redefined the medical management of the infant with persistent pulmonary hypertension of the newborn (PPHN). With a selective pulmonary vasodilator in hand, a kinder, gentler approach to ventilation was embraced in many neonatal intensive care units, aggressive hyperventilation and alkaline therapy were abandoned, and the number of infants referred for extracorporeal membrane oxygenation (ECMO) declined. Yet, iNO is not a panacea. A significant number of infants fail to respond or sustain a response to iNO. Furthermore, iNO is being increasingly used off-label for populations in which its safety and efficacy have not been adequately studied. In this chapter on iNO in children, we will review the spectrum of approved and off-label uses of iNO in pediatrics, and address gaps in our knowledge regarding the optimal dosing, weaning, and patient selection.

Glutathione plays a crucial role in free radical scavenging, oxidative injury, and cellular homeostasis. Previously, we identified a non-synonymous polymorphism (P462S) in the gene encoding the catalytic subunit of glutamate-cysteine ligase (GCLC), the rate-limiting enzyme in glutathione biosynthesis. This polymorphism is present only in individuals of African descent. Presently, we report that this ethnic-specific polymorphism (462S) encodes an enzyme with significantly decreased in vitro activity when expressed by either a bacterial or mammalian cell expression system. In addition, overexpression of the 462P wild-type GCLC enzyme results in higher intracellular glutathione concentrations than overexpression of the 462S isoform. We also demonstrate that apoptotically stimulated mammalian cells overexpressing the 462S enzyme have increased caspase activation and increased DNA laddering compared to cells overexpressing the wild-type 462P enzyme. Finally, we genotyped several African and African-descent populations and demonstrate that the 462S polymorphism is in Hardy-Weinberg disequilibrium, with no individuals homozygous for the 462S polymorphism identified. These findings describe a glutathione production pathway polymorphism present in individuals of African descent with significantly decreased in vitro activity.

Children with congenital heart defects are at risk for perioperative pulmonary hypertension if they require corrective or palliative surgery in the first week of life or if they have defects associated with significant pulmonary overcirculation. In addition, children undergoing cavopulmonary connections for single ventricle lesions require low pulmonary vascular resistance for surgical success. Treatment of perioperative pulmonary hypertension with inhaled nitric oxide has become standard therapy in many centers. Related drugs that increase nitric oxide synthesis, including arginine and citrulline, have also been studied in the perioperative period. In this article, previous clinical trials of inhaled nitric oxide, intravenous arginine, and intravenous and oral citrulline in children with perioperative pulmonary hypertension or elevated pulmonary vascular resistance after a cavopulmonary connection are reviewed. In addition, recommendations are presented for each agent on the clinical use in the perioperative setting including clinical indications, assessment of clinical effect, and length of therapy.

Newborn piglets develop pulmonary hypertension and have diminished pulmonary vascular nitric oxide (NO) production when exposed to chronic hypoxia. NO is produced by endothelial NO synthase (eNOS) in the pulmonary vascular endothelium using l-arginine as a substrate and producing l-citrulline as a byproduct. l-Citrulline is metabolized to l-arginine by two enzymes that are colocated with eNOS in pulmonary vascular endothelial cells. The purpose of this study was to determine whether oral supplementation with l-citrulline during exposure of newborn piglets to 10 days of chronic hypoxia would prevent the development of pulmonary hypertension and increase pulmonary NO production. A total of 17 hypoxic and 17 normoxic control piglets were studied. Six of the 17 hypoxic piglets were supplemented with oral l-citrulline starting on the first day of hypoxia. l-Citrulline supplementation was provided orally twice a day. After 10 days of hypoxia or normoxia, the animals were anesthetized, hemodynamic measurements were performed, and the lungs were perfused in situ. Pulmonary arterial pressure and pulmonary vascular resistance were significantly lower in hypoxic animals treated with l-citrulline compared with untreated hypoxic animals ( P < 0.001). In vivo exhaled NO production ( P = 0.03) and nitrite/nitrate accumulation in the perfusate of isolated lungs ( P = 0.04) were significantly higher in l-citrulline-treated hypoxic animals compared with untreated hypoxic animals. l-Citrulline supplementation ameliorated the development of pulmonary hypertension and increased NO production in piglets exposed to chronic hypoxia. We speculate that l-citrulline may benefit neonates exposed to prolonged periods of hypoxia from cardiac or pulmonary causes.

Pediatric cases of fulminant community-associated methicillin-resistant Staphylococcus aureus (MRSA) infections requiring extracorporeal life support (ECLS) have been reported, but the frequency of ECLS use for severe presentations of staphylococcal disease is unknown.To describe the frequency and characteristics of children with MRSA infections requiring ECLS using local and international databases.The reasons for use of ECLS in children 0-18 yrs of age were determined in both the Vanderbilt Children's Hospital medical record system and the Extracorporeal Life Support Organization database during the years 1994-2005. Demographic characteristics, ventilatory management, and measurements of cardiopulmonary status in subjects undergoing ECLS with a pre-ECLS diagnosis of infection with Staphylococcus aureus and MRSA were included.Three subjects with MRSA sepsis requiring ECLS were identified at Vanderbilt since 2000. Before that time, no cases due to MRSA were reported. The three subjects were previously healthy adolescents with severe necrotizing pneumonia associated with skin/soft-tissue infection and two died. A total of 45 patients requiring ECLS for MRSA infection were identified in the International Extracorporeal Life Support Organization database, with nearly half reported in the past 2 yrs (20 of 45 patients). The median age was 2.4 yrs (interquartile range, 0.36-14 yrs), with peaks noted in infancy and adolescence. In Extracorporeal Life Support Organization subjects with MRSA, survival to discharge was highest in infants and young children aged 1-4 yrs (65% and 71%, respectively) and lowest in the age ranges of 5-9 yrs and 13-18 yrs (0% and 31%, respectively). There were no statistically significant differences in pre-ECLS ventilatory settings, cardiopulmonary status, or frequency of complications between survivors and nonsurvivors.The use of ECLS for MRSA infection seems to be increasing both locally and internationally. High mortality rates, particularly in older patients, are concerning and highlight the increasing problem with this pathogen.

Increased pulmonary artery pressure (PAP) can complicate the postoperative care of children undergoing surgical repair of congenital heart defects. Endogenous NO regulates PAP and is derived from arginine supplied by the urea cycle. The rate-limiting step in the urea cycle is catalyzed by a mitochondrial enzyme, carbamoyl-phosphate synthetase I (CPSI). A well-characterized polymorphism in the gene encoding CPSI (T1405N) has previously been implicated in neonatal pulmonary hypertension. A consecutive modeling cohort of children (N=131) with congenital heart defects requiring surgery was prospectively evaluated to determine key factors associated with increased postoperative PAP, defined as a mean PAP > 20mmHg for at least one hour during the 48 hours following surgery measured by an indwelling pulmonary artery catheter. Multiple Dimensionality Reduction (MDR) was used to both internally validate observations and develop optimal two-variable through five-variable models that were tested prospectively in a validation cohort (N= 41). Unconditional logistic regression analysis of the modeling cohort revealed that age (OR= 0.92, p=0.01), CPSI T1405N genotype (AC vs. AA: OR=4.08, p=0.04, CC vs. AA: OR=5.96, p=0.01), and Down syndrome (OR=5.25, p=0.04) were independent predictors of this complex phenotype. MDR predicted that the best two-variable model consisted of age and CPSI T1405N genotype (p

Objective The study sought to determine whether citrulline supplementation, a precursor to nitric oxide synthesis, is safe and efficacious in increasing plasma citrulline concentrations and decreasing the risk of postoperative pulmonary hypertension. Study Design Forty children, undergoing cardiopulmonary bypass and at risk for pulmonary hypertension, were randomized to receive 5 perioperative doses (1.9 g/m 2 per dose) of either oral citrulline or placebo. Plasma citrulline and arginine concentrations were measured at 5 time points. Measurements of systemic blood pressure and presence of pulmonary hypertension were collected. Results Median citrulline concentrations were significantly higher in the citrulline group versus the placebo group immediately postoperatively (36 μmol/L vs 26 μmol/L, P = .012) and at 12 hours postoperatively (37 μmol/L vs 20 μmol/L, P = .015). Mean plasma arginine concentrations were significantly higher in the citrulline group versus the placebo group by 12 hours postoperatively (36 μmol/L vs 23 μmol/L, P = .037). Mean systemic blood pressure did not differ between groups ( P = .53). Postoperative pulmonary hypertension developed in 9 patients, 6 of 20 (30%) in the placebo group and 3 of 20 (15%) in the citrulline group ( P = .451), all of whom had plasma citrulline concentrations less than age-specific norms. Postoperative pulmonary hypertension did not develop in patients who demonstrated plasma citrulline concentrations in excess of 37 μmol/L ( P = .036). Conclusions Oral citrulline supplementation safely increased plasma citrulline and arginine concentrations compared with placebo after cardiopulmonary bypass. Postoperative pulmonary hypertension did not occur in children with naturally elevated citrulline levels or elevations through supplementation. Oral citrulline supplementation may be effective in reducing postoperative pulmonary hypertension.

Carbamyl phosphate synthetase I (CPSI) determines the rate-limiting entry of free ammonia into the urea cycle. Disruption of CPSI affects the liver's ability to remove waste nitrogen and produce arginine, citrulline, and urea. Arginine is the necessary precursor for the critical biomolecule, nitric oxide (NO). We have studied the classic model of CPSI deficiency, which results in severe hyperammonemia, and identified a large number of molecular defects. A number of CPSI polymorphisms have been found that appear to result in functional consequences. We have examined the association of these polymorphisms with various environmental stress conditions and found that certain CPSI alleles are associated with clinical outcome. We refer to these associations as environmentally determined genetic expression (EDGE) affects. In addition to studies of classic CPSI deficiency, we have developed data for the EDGE concept in post-cardiac surgery-related pulmonary hypertension, hepatic veno-occlusive disease after bone marrow transplantation, and persistent pulmonary hypertension of the newborn. We have linked these outcomes and genotypes to the availability of the urea cycle intermediates, citrulline and arginine, and their role in NO synthesis. We hypothesize that these polymorphisms affect the functional efficiency of CPSI and thus the entire urea cycle and as such, the availability of the NO substrates. By piecing together the various functional aspects of the urea cycle changes we have seen, we can better understand the clinical vulnerabilities of patients in environmentally stressful situations. This knowledge should allow us to design intervention strategies to either predict or modify the associated adverse outcomes.

Objective To test the hypothesis that cardiopulmonary bypass used for repair of ventricular septal defects and atrioventricular septal defects would decrease availability of urea cycle intermediates including arginine and subsequent nitric oxide availability. Study design Consecutive infants (n = 26) undergoing cardiopulmonary bypass for repair of an unrestrictive ventricular septal defect or atrioventricular septal defect were studied. Blood samples were collected immediately before surgery, immediately after surgery, and 12 hours, 24 hours, and 48 hours after surgery. Urea cycle intermediates, including citrulline, arginine, and ornithine, were measured by amino acid analysis. Nitric oxide metabolites were measured by means of the modified Griess reaction. Results Cardiopulmonary bypass caused a significant decrease in the urea cycle intermediates arginine, citrulline, and ornithine at all postoperative time points compared with preoperative levels. The ratio of ornithine to citrulline, a marker of urea cycle function, was elevated at all postoperative time points compared with preoperative values, indicating decreased urea cycle function. Nitric oxide metabolites were significantly decreased at all postoperative time points except for 48 hours, compared with preoperative levels. Conclusions Cardiopulmonary bypass significantly decreases availability of arginine, citrulline, and nitric oxide metabolites in the postoperative period. Decreased availability of nitric oxide precursors may contribute to the increased risk of postoperative pulmonary hypertension. (J Pediatr 2003;142:26-30)

The tripeptide glutathione is an important biomolecule that acts as a scavenger of free radicals and plays a role in a number of other cellular processes. A number of diseases, including Parkinson's disease, cancer, sickle cell anemia, and HIV infection, are thought to involve oxidative stress and depletion of glutathione. The heterodimeric enzyme glutamate cysteine ligase catalyzes the first, rate-limiting step in the de novo synthesis of glutathione. Functional polymorphisms within the gene encoding the subunits of glutamate cysteine ligase have the potential to affect the body's capacity to synthesize glutathione and thus, may affect those diseases in which oxidative stress and glutathione have roles. We undertook systematic screening for polymorphisms within the exons and intronic flanking sequences of the gene encoding the catalytic subunit of glutamate cysteine ligase (GCLC). We identified 11 polymorphisms in GCLC and established allele frequencies for those polymorphisms in a population fitting the demographics of the middle Tennessee area. The nonsynonymous polymorphism C1384T was found only in individuals of African descent. In addition, allele frequencies for three other polymorphisms differ between Caucasians and African-Americans. Understanding these polymorphisms may lead to better understanding of diseases where glutathione is important so that better treatments may be developed.

We examined early results in infants with hypoplastic left heart syndrome undergoing the Norwood operation with perioperative use of inhaled nitric oxide and application of extracorporeal membrane oxygenation.Medical records were reviewed retrospectively.Between April 1997 and March 2001, 50 infants underwent a modified Norwood operation for hypoplastic left heart syndrome. Mean age at operation was 7.5 +/- 5.7 days, and mean weight was 3.1 +/- 0.5 kg. Five infants had a delayed operation because of sepsis. The mean diameter of the ascending aorta by echocardiography was 3.6 +/- 1.8 mm. Ductal cannulation was used to establish cardiopulmonary bypass in all patients. Mean circulatory arrest time was 39.4 +/- 4.8 minutes. The size of the pulmonary-systemic shunt was 3.0 mm in 6 infants, 3.5 mm in 37, and 4.0 mm in 7. Infants with persistent hypoxia (partial pressure of oxygen30 mm Hg) received nitric oxide after they were weaned from cardiopulmonary bypass. Extracorporeal membrane oxygenation was initiated in 8 infants in the pediatric intensive care unit primarily for low cardiac output and in 8 in the operating room because of the inability to separate them from cardiopulmonary bypass. The 30-day mortality rate was 22% (11 of 50 patients), and the hospital mortality rate was 32% (16 of 50 patients). Mean follow-up was 17 months. Ten patients (20%) underwent stage-two repair, with one operative death. One survivor had a Fontan procedure, and 2 underwent heart transplantation, with one death.Early application of extracorporeal membrane oxygenation for hemodynamic instability and selective use of nitric oxide for persistent hypoxia in the immediate postoperative period may improve survival of patients with hypoplastic left heart syndrome. Renal failure requiring hemofiltration during extracorporeal membrane oxygenation (p0.05) and cardiopulmonary arrest in the pediatric intensive care unit (p0.05) were predictors of hospital mortality.

Surfactant protein (SP)-A is a known opsonin for a variety of pulmonary pathogens. SP-A enhances ingestion of these pathogens by interaction with an SP-A receptor (SP-AR) found on phagocytic cells such as peripheral blood monocytes (PBMC) and alveolar macrophages. Respiratory syncytial virus (RSV) is the most important respiratory pathogen in children. Recent studies have indicated that SP-A levels may be decreased in RSV bronchiolitis and pneumonia. In this study we examined the role of SP-A in uptake of RSV by both PBMC and U937 macrophages, a human macrophage cell line known to express SP-ARs. In addition, we studied the effect of SP-A- mediated uptake of RSV on production of tumor necrosis factor (TNF)-alpha and interleukin (IL)-10 by these cells because incomplete immunity to recurrent RSV infection has been partially attributed to abnormal cytokine responses by macrophages. SP-A enhanced binding and uptake of fluorescently labeled RSV (RSV-FITC) by PBMC in a dose-dependent manner, with a maximal effect seen with 10 to 15 microg/ml SP-A as measured by both percent fluorescent monocytes and linear mean fluorescence (lmf) of individual cells. SP-A also enhanced uptake of RSV-FITC by U937 macrophages, with a maximal effect seen with 20 microg/ml SP-A as measured by both percent fluorescent monocytes and lmf. With respect to TNF-alpha levels, RSV alone slightly enhanced TNF-alpha production by PBMC and decreased TNF-alpha production by U937 macrophages measured at 12 h after addition of RSV. SP-A-mediated uptake of RSV significantly enhanced TNF-alpha production by PBMC and reversed the RSV-induced depression of TNF-alpha by U937 macrophages. RSV significantly enhanced IL-10 production by both cell types, which was reversed by SP-A-mediated uptake. These findings suggest that SP-A is an important opsonin for RSV and that SP-A-mediated uptake of RSV may alter some of the unusual cytokine responses that are postulated to be involved in incomplete immunity to recurrent infection.

Inhaled racemic epinephrine relieves airway obstruction in patients with respiratory syncytial virus bronchiolitis. The contribution of alpha- versus beta-adrenoreceptor stimulation toward this clinical effect is unknown. We describe an infant treated with propranolol for supraventricular tachycardia in whom respiratory syncytial virus bronchiolitis developed. Inhaled racemic epinephrine improved his respiratory symptoms, whereas nebulized albuterol did not.

Pulmonary surfactant exists in the alveolus in several distinct subtypes that differ in their morphology, composition, and surface activity. Experiments by others have implicated a serine hydrolase in the production of the inactive small vesicular subtype of surfactant (N. J. Gross and R. M. Schultz. Biochim. Biophys. Acta 1044: 222–230, 1990). Our laboratory recently identified this enzyme in the rat as the serine carboxylesterase ES-2 [F. Barr, H. Clark, and S. Hawgood. Am. J. Physiol. 274 ( Lung Cell. Mol. Physiol. 18): L404–L410, 1998]. In the present study, we determined the cellular sites of expression of ES-2 in rat lung using a digoxygenin-labeled ES-2 riboprobe. ES-2 mRNA was localized to type II cells and alveolar macrophages but not to Clara cells. Using a specific ES-2 antibody, we determined the protein distribution of ES-2 in the lung by immunohistochemistry, and it was found to be consistent with the sites of mRNA expression. Most of the ES-2 in rat bronchoalveolar lavage is in the surfactant-depleted supernatant, but ES-2 was also consistently localized to the small vesicular surfactant subfraction presumed to form as a consequence of conversion activity. These results are consistent with a role for endogenous lung ES-2 in surfactant metabolism.

ContextIn uncontrolled clinical studies, prone positioning appeared to be safe and to improve oxygenation in pediatric patients with acute lung injury. However, the effect of prone positioning on clinical outcomes in children is not known.ObjectiveTo test the hypothesis that at the end of 28 days infants and children with acute lung injury treated with prone positioning would have more ventilator-free days than those treated with supine positioning.Design, Setting, and PatientsMulticenter, randomized, controlled clinical trial conducted from August 28, 2001, to April 23, 2004, of 102 pediatric patients from 7 US pediatric intensive care units aged 2 weeks to 18 years who were treated with supine vs prone positioning. Randomization was concealed and group assignment was not blinded.InterventionPatients were randomized to either supine or prone positioning within 48 hours of meeting acute lung injury criteria, with those patients in the prone group being positioned within 4 hours of randomization and remaining prone for 20 hours each day during the acute phase of their illness for a maximum of 7 days, after which they were positioned supine. Both groups were treated using lung protective ventilator and sedation protocols, extubation readiness testing, and hemodynamic, nutrition, and skin care guidelines.Main Outcome MeasureVentilator-free days to day 28.ResultsThe trial was stopped at the planned interim analysis on the basis of the prespecified futility stopping rule. There were no differences in the number of ventilator-free days between the 2 groups (mean [SD], 15.8 [8.5] supine vs 15.6 [8.6] prone; mean difference, −0.2 days; 95% CI, −3.6 to 3.2; P = .91). After controlling for age, Pediatric Risk of Mortality III score, direct vs indirect acute lung injury, and mode of mechanical ventilation at enrollment, the adjusted difference in ventilator-free days was 0.3 days (95% CI, −3.0 to 3.5; P = .87). There were no differences in the secondary end points, including proportion alive and ventilator-free on day 28 (P = .45), mortality from all causes (P>.99), the time to recovery of lung injury (P = .78), organ-failure−free days (P = .88), and cognitive impairment (P = .16) or overall functional health (P = .12) at hospital discharge or on day 28.ConclusionProne positioning does not significantly reduce ventilator-free days or improve other clinical outcomes in pediatric patients with acute lung injury.