Frederick E. Barr

Diagnosing delirium in critically ill children: Validity and reliability of the Pediatric Confusion Assessment Method for the Intensive Care Unit*

Objective:To validate a diagnostic instrument for pediatric delirium in critically ill children, both ventilated and nonventilated, that uses standardized, developmentally appropriate measurements. Design and Setting: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. Patients:A total of 68 pediatric critically ill patients, at least 5 years of age, were enrolled from July 1, 2008, to March 30, 2009. Interventions:None. Measurements: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. Results: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 (&kgr; = 0.96; 95% confidence interval, 0.74–1.0). Conclusions: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.

l-Citrulline ameliorates chronic hypoxia-induced pulmonary hypertension in newborn piglets

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.

Modified Norwood operation for hypoplastic left heart syndrome

BACKGROUND 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. METHODS Medical records were reviewed retrospectively. RESULTS 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 oxygen < 30 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. CONCLUSIONS 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 (p < 0.05) and cardiopulmonary arrest in the pediatric intensive care unit (p < 0.05) were predictors of hospital mortality.

Quantitative RT-PCR Comparison of the Urea and Nitric Oxide Cycle Gene Transcripts in Adult Human Tissues

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.

Increasing use of extracorporeal life support in methicillin-resistant staphylococcus aureus sepsis in children*

Background: 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. Objective: To describe the frequency and characteristics of children with MRSA infections requiring ECLS using local and international databases. Methods: The reasons for use of ECLS in children 0–18 yrs of age were determined in both the Vanderbilt Childrens 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. Results: 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. Conclusions: 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.

Use of high-dose corticosteroids and high-frequency oscillatory ventilation for treatment of a child with diffuse alveolar hemorrhage after bone marrow transplantation : Case report and review of the literature

Background: 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. Patient: 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. Intervention: The child was treated with high‐dose corticosteroids and high‐frequency oscillatory ventilation and experienced a complete clinical recovery from her pulmonary disease. Results: 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. Conclusion: This case supports the contention that early treatment with high‐dose corticosteroids is warranted in children with DAH after BMT.

Ethnic diversity in a critical gene responsible for glutathione synthesis

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 Parkinsons 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 bodys 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.

Inhaled Nitric Oxide and Related Therapies

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.

Delirium: An Emerging Frontier in the Management of 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.

An ethnic-specific polymorphism in the catalytic subunit of glutamate-cysteine ligase impairs the production of glutathione intermediates in vitro.

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.