Utility of Point-of-Care Lung Ultrasonography for Evaluating Acute Chest Syndrome in Young Patients With Sickle Cell Disease.

STUDY OBJECTIVE: Acute chest syndrome is a leading cause of mortality in patients with sickle cell disease (SCD). Because early detection of acute chest syndrome is directly tied to prognosis, young patients with SCD undergo countless chest radiography screenings throughout their lifetime for commonly occurring acute chest syndrome risk factors such as fever, chest pain, or cough. Chest radiography is not an ideal screening method because it is associated with radiation exposure, which accumulates with repeated imaging. Point-of-care lung ultrasonography is a nonradiating imaging modality that has been used to identify other lung pathology and may have a role in SCD. The goal of this study was to determine the accuracy of point-of-care lung ultrasound to identify an infiltrate suggestive of acute chest syndrome in patients with SCD compared to chest radiography as the gold standard. METHODS: This was a prospective observational study in 2 urban pediatric emergency departments to evaluate the accuracy of point-of-care lung ultrasonography in identifying patients with SCD who were aged 0 to 21 years and had an infiltrate suggestive of acute chest syndrome compared with chest radiography. Clinicians and trainees with point-of-care lung ultrasonographic training obtained informed consent and performed investigational point-of-care lung ultrasonography to evaluate for lung consolidation. A blinded point-of-care lung ultrasonographic expert reviewed results for quality assurance and agreement. Accuracy, sensitivity, specificity, likelihood ratios, and positive and negative predictive value were calculated for point-of-care lung ultrasonography test performance characteristics, with chest radiography as a reference standard. RESULTS: Point-of-care lung ultrasonography was performed on 191 SCD patients with a mean age of 8 years; 41% were female patients, and there was a 17% prevalence of acute chest syndrome. Accuracy of point-of-care lung ultrasonography to detected acute chest syndrome was 92%, sensitivity was 88%, and specificity was 93% compared with that for chest radiography. CONCLUSION: Point-of-care lung ultrasonography is a feasible alternative to chest radiography for screening for acute chest syndrome in young patients with SCD. Further studies are needed to determine how this test performs within clinical practice.

Hydroxyurea effectiveness in children and adolescents with sickle cell anemia: A large retrospective, population-based cohort.

The clinical efficacy of hydroxyurea in patients with sickle cell anemia (SCA) has been well established. However, data about its clinical effectiveness in practice is limited. We evaluated the clinical effectiveness of hydroxyurea in a large pediatric population using a retrospective cohort, pre-post treatment study design to control for disease severity selection bias. The cohort included children with SCA (SS, Sß0 thalassemia) who received care at Children's Healthcare of Atlanta (CHOA) and who initiated hydroxyurea in 2009-2011. Children on chronic transfusions, or children with inadequate follow up data and/or children who had taken hydroxyurea in the 3 years prior were excluded. For each patient healthcare utilization, laboratory values, and clinical outcomes for the 2-year period prior to hydroxyurea initiation were compared to those 2 years after initiation. Of 211 children with SCA who initiated hydroxyurea in 2009-2011, 134 met eligibility criteria. After initiation of hydroxyurea, rates of hospitalizations, pain encounters, and emergency department visits were reduced by 47% (<0.0001), 36% (P = 0.0001) and 43% (P < 0.0001), respectively. Average hemoglobin levels increased by 0.7 g/dl (P < 0.0001). Hydroxyurea effectiveness was similar across gender, insurance types and age, although there was a slightly greater reduction in hospitalizations in younger children. Am. J. Hematol. 92:77-81, 2017. © 2016 Wiley Periodicals, Inc.

Sickle Cell Disease with Cyanotic Congenital Heart Disease: Long-Term Outcomes in 5 Children.

Sickle cell disease is a risk factor for cerebrovascular accidents in the pediatric population. This risk is compounded by hypoxemia. Cyanotic congenital heart disease can expose patients to prolonged hypoxemia. To our knowledge, the long-term outcome of patients who have combined sickle cell and cyanotic congenital heart disease has not been reported. We retrospectively reviewed patient records at our institution and identified 5 patients (3 girls and 2 boys) who had both conditions. Their outcomes were uniformly poor: 4 died (age range, 12 mo-17 yr); 3 had documented cerebrovascular accidents; and 3 developed ventricular dysfunction. The surviving patient had developmental delays. On the basis of this series, we suggest mitigating hypoxemia, and thus the risk of stroke, in patients who have sickle cell disease and cyanotic congenital heart disease. Potential therapies include chronic blood transfusions, hydroxyurea, earlier surgical correction to reduce the duration of hypoxemia, and heart or bone marrow transplantation.

Extracellular hemin crisis triggers acute chest syndrome in sickle mice.

The prevention and treatment of acute chest syndrome (ACS) is a major clinical concern in sickle cell disease (SCD). However, the mechanism underlying the pathogenesis of ACS remains elusive. We tested the hypothesis that the hemolysis byproduct hemin elicits events that induce ACS. Infusion of a low dose of hemin caused acute intravascular hemolysis and autoamplification of extracellular hemin in transgenic sickle mice, but not in sickle-trait littermates. The sickle mice developed multiple symptoms typical of ACS and succumbed rapidly. Pharmacologic inhibition of TLR4 and hemopexin replacement therapy prior to hemin infusion protected sickle mice from developing ACS. Replication of the ACS-like phenotype in nonsickle mice revealed that the mechanism of lung injury due to extracellular hemin is independent of SCD. Using genetic and bone marrow chimeric tools, we confirmed that TLR4 expressed in nonhematopoietic vascular tissues mediated this lethal type of acute lung injury. Respiratory failure was averted after the onset of ACS-like symptoms in sickle mice by treating them with recombinant hemopexin. Our results reveal a mechanism that helps to explain the pathogenesis of ACS, and we provide proof of principle for therapeutic strategies to prevent and treat this condition in mice.

Association between plasma free haem and incidence of vaso-occlusive episodes and acute chest syndrome in children with sickle cell disease.

We tested the hypothesis that extracellular haem is linked to the incidence of acute complications of sickle cell disease (SCD). Using multivariable regression analysis, higher plasma free haem, but not total plasma haem, was associated with increased odds of vaso-occlusive crisis (VOC) [P = 0·028, odds ratio (OR); 2·05, 95% Confidence Interval (CI) = 1·08-3·89] and acute chest syndrome (ACS) [P = 0·016, OR; 2·56, CI = 1·19, 5·47], after adjusting for age and gender in children with SCD. These findings suggest that haem and factors that influence its concentration in plasma may be informative of the risk of VOC and ACS in SCD patients.

Alloimmunization to transfused HOD red blood cells is not increased in mice with sickle cell disease.

BACKGROUND: Increased rates of red blood cell (RBC) alloimmunization in patients with sickle cell disease may be due to transfusion frequency, genetic predisposition, or immune dysregulation. To test the hypothesis that sickle cell pathophysiology influences RBC alloimmunization, we utilized two transgenic mouse models of sickle cell disease. STUDY DESIGN AND METHODS: Transgenic sickle mice, which express human α and ß(S) globin, were transfused with fresh or 14-day-stored RBCs containing the HOD (hen egg lysozyme, ovalbumin, and human Duffy(b) ) antigen; some recipients were inflamed with poly(I : C) before transfusion. Anti-HOD alloantibody responses were subsequently measured by enzyme-linked immunosorbent assay and flow crossmatch; a cohort of recipients had posttransfusion serum cytokines measured by bead array. RESULTS: Both Berkeley and Townes homozygous (SS) and heterozygous (AS) mice had similar rates and magnitude of anti-HOD RBC alloimmunization after fresh HOD RBC transfusion compared with control animals; under no tested condition did homozygous SS recipients make higher levels of alloantibodies than control animals. Unexpectedly, homozygous SS recipients had blunted cytokine responses and lower levels of anti-HOD alloantibodies after transfusion of 14-day stored RBCs, compared with control animals. CONCLUSIONS: In sum, homozygous ß(S) expression and the ensuing disease state are not alone sufficient to enhance RBC alloimmunization to transfused HOD RBCs in two distinct humanized murine models of sickle cell disease under the conditions examined. These data suggest that other factors may contribute to the high rates of RBC alloimmunization observed in humans with sickle cell disease.

Global gene expression profiling of endothelium exposed to heme reveals an organ-specific induction of cytoprotective enzymes in sickle cell disease.

BACKGROUND: Sickle cell disease (SCD) is characterized by hemolysis, vaso-occlusion and ischemia reperfusion injury. These events cause endothelial dysfunction and vasculopathies in multiple systems. However, the lack of atherosclerotic lesions has led to the idea that there are adaptive mechanisms that protect the endothelium from major vascular insults in SCD patients. The molecular bases for this phenomenon are poorly defined. This study was designed to identify the global profile of genes induced by heme in the endothelium, and assess expression of the heme-inducible cytoprotective enzymes in major organs impacted by SCD. METHODS AND FINDINGS: Total RNA isolated from heme-treated endothelial monolayers was screened with the Affymetrix U133 Plus 2.0 chip, and the microarray data analyzed using multiple bioinformatics software. Hierarchical cluster analysis of significantly differentially expressed genes successfully segregated heme and vehicle-treated endothelium. Validation studies showed that the induction of cytoprotective enzymes by heme was influenced by the origin of endothelial cells, the duration of treatment, as well as the magnitude of induction of individual enzymes. In agreement with these heterogeneities, we found that induction of two major Nrf2-regulated cytoprotective enzymes, heme oxygenase-1 and NAD(P)H:quinone oxidoreductase-1 is organ-specific in two transgenic mouse models of SCD. This data was confirmed in the endothelium of post-mortem lung tissues of SCD patients. CONCLUSIONS: Individual organ systems induce unique profiles of cytoprotective enzymes to neutralize heme in SCD. Understanding this heterogeneity may help to develop effective therapies to manage vasculopathies of individual systems.

Polycythemia in an infant secondary to granulocyte transfusions.

Granulocyte transfusions may be useful for neutropenic pediatric patients with refractory bacterial or fungal infections. Many potential adverse sequelae associated with granulocyte transfusions are well recognized, including febrile reactions, fluid overload, alloimmunization, and lung injury. Other potential adverse sequelae, however, are less well known. This case report describes an infant with familial hemophagocytic lymphohistiocytosis who developed polycythemia (hemoglobin 10-17.6 g/dl) following four daily transfusions of 20 ml/kg of apheresis collected, steroid stimulated donor granulocytes. Expanded knowledge of potential risks of transfused granulocytes will allow for rapid recognition of transfusion-related complications, should they occur.