Sustained increase in annual transcranial Doppler screening rates in children with sickle cell disease: A quality improvement project.

INTRODUCTION: Individuals with sickle cell disease (SCD) at increased risk for stroke should undergo annual stroke risk assessment using transcranial Doppler (TCD) screening between the ages of 2 and 16. Though this screening can significantly reduce morbidity associated with SCD, screening rates at Boston Children's Hospital (and nationwide) remain below the recommended 100% screening adherence rates. METHODS: Three plan-do-study-act (PDSA) cycles were designed and implemented. The Specific, Measurable, Achievable, Relevant, and Time-Bound (SMART) aim of our quality improvement (QI) initiative was to sustainably increase the proportion of eligible patients receiving a TCD within 15 months of their last TCD to greater than 95%. An interrupted time series (ITS) analysis was performed, comparing TCD adherence rates from PDSA Cycle 1 to those from PDSA Cycles 2 and 3. RESULTS: Mean TCD adherence increased across all three PDSA cycles, from a baseline of 67% in the first cycle (January 2015 to September 2020) to 92% in the third cycle (May 2021 to March 2023). In the ITS analysis of TCD adherence rates, there was a significant difference in the final TCD adherence rate achieved compared to the rate predicted, with a total estimated increase in adherence of 17.9% being attributable to the interventions from PDSA Cycles 2 and 3. DISCUSSION: Although other QI initiatives had demonstrated ability to increase adherence to TCD screening for patients with SCD, this is the first QI project to collect data over such a prolonged period of time to demonstrate a sustained increase in screening rates throughout the intervention (an 8-year period).

The Risk of Kidney Injury in Patients With Sickle Cell Disease Treated With Ketorolac for Acute Pain.

Ketorolac, a nonsteroidal anti-inflammatory drug, is used in combination with opioids to manage vaso-occlusive episodes (VOEs). The relationship between ketorolac use and kidney injury in pediatric patients with sickle cell disease (SCD) remains incompletely understood. We hypothesize that ketorolac is associated with acute kidney injury (AKI) in patients with SCD presenting with pain. All nonsurgical hospitalizations for VOEs treated with ketorolac between January 2014 and December 2022 were included. We used optimal matching methodology to identify control admissions (2:1 ratio) and used nonparametric tests to compare ketorolac administration between cases and controls. A total of 1319 encounters/253 patients were included in this study. AKI was noted in 1.1% of encounters and 5.5% of patients. Cases had significantly higher initial BUN than controls (9.0 vs. 6.0 mg/dL, P =0.012). In cases versus controls, there was significantly lower serum sodium (136.0 vs. 138.0 mmol/L, P =0.021). There was no association between ketorolac dose and development of AKI among children with SCD. Higher BUN and lower sodium in cases suggest that patients with AKI were more volume depleted on admission than controls. This highlights the need for strict assessment of fluid status upon admission for VOE.

Genetic Modifiers of Stroke in Patients with Sickle Cell Disease-A Scoping Review.

Sickle cell disease (SCD) clinically manifests itself with a myriad of complications. Stroke, both ischemic and hemorrhagic, as well as silent white matter changes, occurs at a relatively high prevalence. Understanding why and in whom stroke is most likely to occur is critical to the effective prevention and treatment of individuals with SCD. Genetic studies, including genome- and exome-wide association studies (GWAS and EWAS), have found several key modifiers associated with increased stroke/stroke risk in SCD via mechanisms including Hemoglobin F (HbF) modulation, inflammation, cellular adhesion, endothelial disruption, and hemolysis. We present a review on the modifiers that have most clearly demonstrated an association to date. More studies are needed to validate other potential polymorphisms and identify new ones. Incorporating gene-focused screenings in clinical care could provide avenues for more targeted, more effective, and less toxic prevention of stroke in this population. The data from this review will be used to inform the initial GWAS performed by the International Hemoglobinopathy Research Network (INHERENT) consortium.

F-erythrocytes promote Plasmodium falciparum proliferation in sickle cell disease.

BACKGROUND: Sickle cell disease (SCD) remains prevalent because heterozygous carriers (HbAS) are partially resistant to Plasmodium falciparum malaria. Sickle hemoglobin (HbS) polymerization in low and intermediate oxygen (O2 ) conditions is the main driver of HbAS-driven resistance to P. falciparum malaria. However, epidemiological studies have reported mixed malaria morbidity and mortality outcomes in individuals with sickle cell disease (SCD). While maximum-tolerated dose hydroxyurea has been shown to lower malaria incidence, fetal hemoglobin (HbF), an inhibitor of HbS polymerization that is variably packaged in F-erythrocytes, might provide hemoglobin that is accessible to the parasite for feeding. METHODS: To explore that risk, we examined the effect of variable mean corpuscular fetal hemoglobin (MCHF) on P. falciparum proliferation, invasion, and development in HbSS RBCs. RESULTS: We found that greater MCHF in HbSS red blood cells (RBCs) is associated with increased P. falciparum proliferation in O2 environments comparable with the microcirculation. Moreover, both parasite invasion and intracellular growth, the major components of proliferation, occur predominantly in F-erythrocytes and are augmented with increasing MCHF. CONCLUSIONS: HbF modifies P. falciparum infection in HbSS RBCs, further highlighting the complexity of the molecular interactions between these two diseases. Other inhibitors of HbS polymerization that do not increase HbF or F-erythrocytes should be independently assessed for their effects on P. falciparum malaria proliferation in HbSS RBCs.

Ketamine use for management of vaso-occlusive pain in pediatric sickle cell disease.

BACKGROUND: Typical sickle cell disease (SCD) vaso-occlusive pain episode (VOE) management includes opioids, which are often inadequate and can be associated with significant side effects. Ketamine, a dissociative anesthetic, is a potentially effective adjunct to VOE management. OBJECTIVES: This study aimed to characterize ketamine use for VOE management in pediatric SCD. METHOD: This retrospective case series summarizes a single-center experience regarding the use of ketamine for inpatient management of pediatric VOE in 156 admissions from 2014 to 2020. RESULTS: Continuous low-dose ketamine infusion was most commonly prescribed to adolescents and young adults as an adjunct to opioids (median starting dose 2.0 µg/kg/min; median maximum dose 3.0 µg/kg/min). Ketamine was started a median of 13.7 hours after admission. Median ketamine infusion duration was 3 days. In most encounters, ketamine infusion was discontinued prior to opioid patient-controlled analgesia (PCA) discontinuation. The majority of encounters (79.3%) had a reduction in either PCA dose, continuous opioid infusion, or both while receiving ketamine. Low-dose ketamine infusion was associated with side effects noted in 21.8% (n = 34) of encounters. The most common side effects included dizziness (5.6%), hallucinations (5.1%), dissociation (2.6%), and sedation (1.9%). There were no reports of ketamine withdrawal. Most patients who received ketamine went on to receive it again during a subsequent admission. CONCLUSION: Further study is needed to determine the optimal timing of ketamine initiation and dosing. The variability of ketamine administration highlights the need for standardized protocols for ketamine use in VOE management.

A systematic review of ketamine for the management of vaso-occlusive pain in sickle cell disease.

Vaso-occlusive episodes (VOEs) are a common complication of sickle cell disease (SCD) and a significant cause of morbidity. Managing VOE pain can be difficult and complex. Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, has been used to manage VOE pain. This systematic literature review synthesizes research published from 2010 to 2020 on the use of ketamine infusion to decrease VOE pain. The review demonstrates that ketamine, a safe and effective treatment for VOE pain, could be considered more widely. However, the significant variability among published clinical studies with regard to dosing, timing of initiation, duration of infusion, and timing of discontinuation highlights the need for standardized ketamine infusion protocols for the management of VOE pain. We conclude with a brief discussion of key components of a potential standardized protocol supported by the literature reviewed as well as areas for future investigation.

Resistance to Plasmodium falciparum in sickle cell trait erythrocytes is driven by oxygen-dependent growth inhibition.

Sickle cell trait (AS) confers partial protection against lethal Plasmodium falciparum malaria. Multiple mechanisms for this have been proposed, with a recent focus on aberrant cytoadherence of parasite-infected red blood cells (RBCs). Here we investigate the mechanistic basis of AS protection through detailed temporal mapping. We find that parasites in AS RBCs maintained at low oxygen concentrations stall at a specific stage in the middle of intracellular growth before DNA replication. We demonstrate that polymerization of sickle hemoglobin (HbS) is responsible for this growth arrest of intraerythrocytic P. falciparum parasites, with normal hemoglobin digestion and growth restored in the presence of carbon monoxide, a gaseous antisickling agent. Modeling of growth inhibition and sequestration revealed that HbS polymerization-induced growth inhibition following cytoadherence is the critical driver of the reduced parasite densities observed in malaria infections of individuals with AS. We conclude that the protective effect of AS derives largely from effective sequestration of infected RBCs into the hypoxic microcirculation.

Erythrocyte ion content and dehydration modulate maximal Gardos channel activity in KCNN4 V282M/+ hereditary xerocytosis red cells.

Hereditary xerocytosis (HX) is caused by missense mutations in either the mechanosensitive cation channel PIEZO1 or the Ca2+-activated K+ channel KCNN4. All HX-associated KCNN4 mutants studied to date have revealed increased current magnitude and red cell dehydration. Baseline KCNN4 activity was increased in HX red cells heterozygous for KCNN4 mutant V282M. However, HX red cells maximally stimulated by Ca2+ ionophore A23187 or by PMCA Ca2+-ATPase inhibitor orthovanadate displayed paradoxically reduced KCNN4 activity. This reduced Ca2+-stimulated mutant KCNN4 activity in HX red cells was associated with unchanged sensitivity to KCNN4 inhibitor senicapoc and KCNN4 activator Ca2+, with slightly elevated Ca2+ uptake and reduced PMCA activity, and with decreased KCNN4 activation by calpain inhibitor PD150606. The altered intracellular monovalent cation content of HX red cells prompted experimental nystatin manipulation of red cell Na and K contents. Nystatin-mediated reduction of intracellular K+ with corresponding increase in intracellular Na+ in wild-type cells to mimic conditions of HX greatly suppressed vanadate-stimulated and A23187-stimulated KCNN4 activity in those wild-type cells. However, conferral of wild-type cation contents on HX red cells failed to restore wild-type-stimulated KCNN4 activity to those HX cells. The phenotype of reduced, maximally stimulated KCNN4 activity was shared by HX erythrocytes expressing heterozygous PIEZO1 mutants R2488Q and V598M, but not by HX erythrocytes expressing heterozygous KCNN4 mutant R352H or PIEZO1 mutant R2456H. Our data suggest that chronic KCNN4-driven red cell dehydration and intracellular cation imbalance can lead to reduced KCNN4 activity in HX and wild-type red cells.

An Increased Risk of Second Malignant Neoplasms After Rhabdomyosarcoma: Population-Based Evidence for a Cancer Predisposition Syndrome?

BACKGROUND: Rhabdomyosarcoma survivors have an increased risk of developing second malignant neoplasms (SMN); this risk is traditionally attributed to the effects of multidisciplinary management required for cure. However, the impact of constitutional predisposition has not been properly analyzed. METHODS: We analyzed the risk of SMN among 1,151 children diagnosed with rhabdomyosarcoma and reported to the Surveillance, Epidemiology, and End Results registries (SEER-9) from 1973 to 2010. Standardized incidence ratios (SIR) and corresponding 95% confidence intervals (CI) were calculated using SEERStat 8.1.2. RESULTS: Children with pleomorphic and embryonal rhabdomyosarcoma had an increased risk of developing a SMN (SIR = 15.77, 95%CI 1.91-56.96 and SIR = 5.6, 95%CI 3.32-8.85, respectively). The risk was age-dependent; the highest was among children <2 years (SIR = 13.38, 95%CI 4.34-31.22) and the lowest was in children >10 years (SIR = 3.35, 95%CI 1.53-6.35). The risk for the youngest patients was higher for those with embryonal rhabdomyosarcoma (SIR = 14.72, 95%CI 4.01-37.70) compared to other histiotypes. Additionally, the risk of SMN was independent of the use of radiation to the primary (SIR = 6.50, 95%CI 3.97-10.03 and SIR = 4.57, 95%CI 2.09-8.68, for children receiving and not receiving radiation, respectively). The pattern of SMN observed was consistent with the Li-Fraumeni spectrum. CONCLUSIONS: Children with rhabdomyosarcoma are at high risk of developing SMN. This risk is higher for a subgroup of young children with pleomorphic and embryonal histologies, and is independent of the use of radiation. This suggests that a subgroup of children with pleomorphic and embryonal rhabdomyosarcoma may have a constitutional cancer predisposition.

Diagnosis of iron-deficient states.

The diagnosis of iron deficiency anemia is typically straightforward, especially when classic biochemical and hematological changes are present in a subject at risk. It can be challenging in the presence of diseases or when it is due to inherited defects of iron metabolism. The identification of iron deficiency prior to anemia development is also difficult. New hematological parameters such as reticulocyte Hb content have expanded the classic ones such as MCV, MCH and MCHC. A variety of hematology analyzers now provide novel parameters to assess cellular hypochromia and microcytosis in both reticulocytes and mature red blood cells. The repertoire of biochemical markers has also been expanded, with iron, transferrin and ferritin being supplemented by circulating transferrin receptor and hepcidin. Molecular identification of functional variants of key iron metabolism determinants has provided explanations for the heritability of some iron metabolism biomarkers. Genetic defects in some of these molecules are responsible for hereditary microcytic anemias, also called atypical microcytic anemias. In this review, we examine the most significant hematological and biochemical markers for iron metabolism, as well as relevant genetic polymorphisms and defects affecting iron handling.

Anaplastic rhabdomyosarcoma in TP53 germline mutation carriers.

BACKGROUND: Rhabdomyosarcoma (RMS) represents a diverse category of myogenic malignancies with marked differences in molecular alterations and histology. This study examines the question if RMS predisposition due to germline TP53 mutations correlates with certain RMS histologies. METHODS: The histology of RMS tumors diagnosed in 8 consecutive children with TP53 germline mutations was reviewed retrospectively. In addition, germline TP53 mutation analysis was performed in 7 children with anaplastic RMS (anRMS) and previously unknown TP53 status. RESULTS: RMS tumors diagnosed in 11 TP53 germline mutation carriers all exhibited nonalveolar, anaplastic histology as evidenced by the presence of enlarged hyperchromatic nuclei with or without atypical mitotic figures. Anaplastic RMS was the first malignant diagnosis for all TP53 germline mutation carriers in this cohort, and median age at diagnosis was 40 months (mean, 40 months ± 15 months; range, 19-67 months). The overall frequency of TP53 germline mutations was 73% (11 of 15 children) in pediatric patients with anRMS. The frequency of TP53 germline mutations in children with anRMS was 100% (5 of 5 children) for those with a family cancer history consistent with Li-Fraumeni syndrome (LFS), and 80% (4 of 5 children) for those without an LFS cancer phenotype. CONCLUSIONS: Individuals harboring germline TP53 mutations are predisposed to develop anRMS at a young age. If future studies in larger anRMS cohorts confirm the findings of this study, the current Chompret criteria for LFS should be extended to include children with anRMS irrespective of family history.

Patient Controlled Analgesia for Vaso-Occlusive Episodes in Children: A Retrospective Study.

OBJECTIVE: To describe Patient-Controlled Analgesia (PCA) administration in pediatric patients admitted with sickle cell vaso-occlusive episode (VOE). METHODS: This single-center retrospective study included all inpatient hematology admissions for VOE between 2014 and 2020. PCA-ratio was calculated as the ratio of bolus over continuous IV opioids dose, and time to PCA adjustment as time between first PCA order and a subsequent order that increased dosing or changed opioid medication. RESULTS: A total of 866 encounters (172 unique patients) with PCA for VOE were included. The mean age was 15.4 years old (SD = 5.0). On average, after admission (hospital arrival), the first opioid dose was given at 1 hour, PCA started at 3.5 hours, and mean length of stay was 4.3 days (SD = 2.5). The mean initial PCA-ratio was 1.7 (SD = 0.6). There were no significant associations between age, gender, initial pain score, or admission hemoglobin and PCA-ratio (linear regression model P = 0.443). In 24.7% of encounters, the PCA was adjusted within 6 hours. After adjusting by age and gender, lower admission pain scores (OR = 1.15, P = 0.004), lower PCA-ratio (OR = 2.1, P = 0.003), longer time to PCA start (OR = 1.2, P = 0.001), and no adjuvant ketamine (OR = 2.4, P < 0.001) were associated with PCA unadjusted within 6 hours. CONCLUSION: At our institution, patients with VOE received opioids and PCA within the first hours of admission. PCAs were started at a ratio of 1.5-1.8, considered normal continuous. While no specific PCA-ratio was clearly superior for pain control, lower ratios (high continuous infusion) were associated with not requiring PCA adjustments at 6 hours. Prospective studies are needed.

Increasing COVID-19 Vaccination Rates for Children With Sickle Cell Disease.

BACKGROUND: The COVID-19 vaccine is important for children with sickle cell disease (SCD). This quality improvement project's objective was to increase the proportion of children with SCD receiving ≥2 COVID-19 vaccine doses to ≥70% by June 2022. METHODS: We used the Model for Improvement framework. We assessed COVID-19 vaccination rates biweekly. Three plan-do-study-act cycles focusing on patient education, provider awareness, and access were performed. Process measures included the outcome of outreach calls and educational video views. Missed clinic appointments was our balancing measure. Line graphs and statistical process control charts were used to track changes. Interrupted time series was used to model implementation rates while accounting for preexisting trends. RESULTS: A total of 243 patients were included. During the preintervention (September 2021-January 2022) and intervention periods (February 2022-June 2022), overall vaccination rates increased from 33% to 41% and 41% to 64%, respectively. Mean vaccination rate in eligible children in each 2-week period increased from 2.1% to 7.2%. The achieved vaccination rate was 11% greater than predicted for patients with SCD. For the general population the achieved vaccination rate was 23% lower than predicted. The proportion of missed visits did not change (9.0% vs. 9.6%). During outreach calls, 10 patients (13.5%) booked a vaccine. Forty percent of patients watched the promotional video. CONCLUSIONS: A significant number of patients with SCD are not vaccinated against COVID-19. Targeting misinformation and improving vaccine access aided in increasing vaccination. Additional interventions are needed as a large number of patients remain unvaccinated.

Genetic reversal of the globin switch concurrently modulates both fetal and sickle hemoglobin and reduces red cell sickling.

We previously reported initial clinical results of post-transcriptional gene silencing of BCL11A expression (NCT03282656) reversing the fetal to adult hemoglobin switch. A goal of this approach is to increase fetal hemoglobin (HbF) expression while coordinately reducing sickle hemoglobin (HbS) expression. The resulting combinatorial effect should prove effective in inhibiting HbS polymerization at lower physiologic oxygen values thereby mitigating disease complications. Here we report results of exploratory single-cell analysis of patients in which BCL11A is targeted molecularly and compare results with cells of patients treated with hydroxyurea (HU), the current standard of care. We use single-cell assays to assess HbF, HbS, oxygen saturation, and hemoglobin polymer content in RBCs for nine gene therapy trial subjects (BCLshmiR, median HbF% = 27.9) and compare them to 10 HU-treated subjects demonstrating high and comparable levels of HbF (HU High Responders, median HbF% = 27.0). All BCL11A patients achieved the primary endpoint for NCT03282656, which was defined by an absolute neutrophil count greater than or equal to 0.5 × 109 cells/L for three consecutive days, achieved within 7 weeks following infusion. Flow cytometric assessment of single-RBC HbF and HbS shows fewer RBCs with high HbS% that would be most susceptible to sickling in BCLshmiR vs. HU High Responders: median 42% of RBCs with HbS%>70% in BCLshmiR vs. 61% in HU High Responders (p = 0.004). BCLshmiR subjects also demonstrate more RBCs resistant to HbS polymerization at lower physiologic oxygen tension: median 32% vs. 25% in HU High Responders (p = 0.006). Gene therapy-induced BCL11A down-regulation reverses the fetal-to-adult hemoglobin switch and induces RBCs with higher HbF%, lower HbS%, and greater resistance to deoxygenation-induced polymerization in clinical trial subjects compared with a cohort of highly responsive hydroxyurea-treated subjects.