Effect of transfusion in acute chest syndrome of sickle cell disease

Role of Steroids in Sickle Cell Patients With Acute Chest Syndrome

Background

The role of corticosteroids to treat acute chest syndrome (ACS) in patients with sickle cell disease (SCD) has always been a matter of debate. In clinical practice, systemic steroids were given for ACS with more severe disease. With the lack of standard treatment guidelines, their use to treat ACS is highly physician-dependent and varies widely across different hospitals. The utility of corticosteroids in ACS remains unclear. The objective of our study was to describe the differences between SCD patients treated with corticosteroids for ACS and those who were not and to evaluate the association between corticosteroid use, length of stay, and readmission rates.

Methodology

We performed a retrospective chart review of patients with SCD ≤18 years of age hospitalized for ACS at Brookdale University Hospital Medical Center between January 2016 and May 2021.

Results

We identified 43 patients with 60 episodes of ACS (median age was 11 years and 55% were males). In total, 32 such episodes were treated with corticosteroids. The use of bronchodilators (p = 0.23), hydroxyurea (p = 0.13), and the presence of fever (p = 0.86) showed no significant difference between the two groups. The need for blood transfusions (p = 0.005), intensive care unit admission (p = 0.031), respiratory support (p = 0.011), and chest X-ray finding with more than one lobe involvement (p = 0.003) all point to moderate or severe ACS, which has been linked to steroid use. The length of hospital stay (p = 0.07) and the readmission rate (p = 0.31) were not statistically significant between the groups. Even in the subgroup with asthma, the length of stay was not different between the groups (p = 0.44).

Conclusions

Our results show that treatment with systemic steroids for ACS is associated with more severe disease. The length of hospital stay was not different between the steroid-treated and untreated groups. Corticosteroids were not associated with a higher readmission rate in our study population, even in ACS patients with comorbid asthma. Further adequately powered prospective trials are needed to investigate the efficacy of corticosteroids in ACS.

High risk and low prevalence diseases: Acute chest syndrome in sickle cell disease

INTRODUCTION

Acute chest syndrome (ACS) in sickle cell disease (SCD) is a serious condition that carries with it a high rate of morbidity and mortality.

OBJECTIVE

This review highlights the pearls and pitfalls of ACS in SCD, including diagnosis and management in the emergency department (ED) based on current evidence.

DISCUSSION

ACS is defined by respiratory symptoms and/or fever and a new radiodensity on chest imaging in a patient with SCD. There are a variety of inciting causes, including infectious and non-infectious etiologies. Although ACS is more common in those with homozygous SCD, clinicians should consider ACS in all SCD patients, as ACS is a leading cause of death in SCD. Patients typically present with or develop respiratory symptoms including fever, cough, chest pain, and shortness of breath, which can progress to respiratory failure requiring mechanical ventilation in 20% of adult patients. However, the initial presentation can vary. While the first line imaging modality is classically chest radiograph, lung ultrasound has demonstrated promise. Further imaging to include computed tomography may be necessary. Management focuses on analgesia, oxygen supplementation, incentive spirometry, bronchodilators, rehydration, antibiotics, consideration for transfusion, and specialist consultation. Empiric antibiotics that cover atypical pathogens are necessary along with measures to increase oxygen-carrying capacity in those with hypoxemia such as simple transfusion or exchange transfusion.

CONCLUSIONS

An understanding of ACS can assist emergency clinicians in diagnosing and managing this potentially deadly disease.

Management of acute chest syndrome in patients with sickle cell disease: a systematic review of randomized clinical trials

INTRODUCTION

Acute chest syndrome (ACS) accounts for the highest mortality in Sickle cell disease patients. Early diagnosis and timely management of ACS results in better outcomes. However, the effectiveness of most treatment modalities for ACS management has not been established.

AREAS COVERED

To review the treatment modalities management protocols and highlight the effectiveness of each option a literature search was done. Randomized controlled trials that assessed the efficacy of different treatment modalities in ACS management in SCD patients were chosen and reviewed.

EXPERT OPINION

11 randomized controlled trials were found that evaluated the efficacy of incentive spirometry, positive expiratory pressure device, intravenous dexamethasone, oral vs. intravenous morphine, inhaled nitric oxide, unfractionated heparin, and blood transfusion in the prevention or treatment of ACS. Although there are guidelines for ACS treatment, the available evidence is very limited to delineating the effectiveness of various interventions in ACS management. More high-quality studies and trials with a larger patient population can benefit this area to support the recommendations with stronger evidence.

Acute Chest Syndrome in Sickle Cell Disease: Clinical Presentation and Outcomes. The Experience of a Single Thalassemia and Sickle Cell Unit in a University Hospital

Acute chest syndrome (ACS) is a common cause of death for sickle cell disease patients. This syndrome is defined as: respiratory symptoms, new X-ray findings developed and/or fever; ACS requires prompt treatment to avoid clinical deterioration and death in adults with sickle cell disease. Sixteen episodes of acute chest syndrome were studied in 16 adults with sickle cell disease. The clinical and radiological findings, treatment, response and outcome of the episode were evaluated respectively. The patient's past history and comorbidities were taken into account in the outcome and days of hospitalization. Fourteen patients recovered with no sequelae; one patient who required mechanical ventilation also recovered; one patient died due to pulmonary emboli. The mean hospitalization days were 7.43.

Therapeutic approach to pediatric patients with acute chest syndrome: national multicenter survey of non invasive ventilation (NIV) and transfusion

BACKGROUND

Intensive care units (ICUs) have seen a spike in the use of noninvasive ventilation (NIV) for many medical conditions. We sought to investigate the attitudes and clinical practice regarding the management of acute chest syndrome (ACS) with a focus on NIV in pediatric ICUs.

METHOD

Members of the French Group for Pediatric Intensive Care Emergencies (GFRUP) were asked to complete an online survey on physicians' attitudes toward children with ACS admitted to the PICU during 2015.

RESULTS

The survey was answered by teams from 17 PICUs (240 beds). In total, 15 centers (88%) had a local transfusion unit and 14 (82%) worked in connection with a sickle cell disease (SCD) reference center. During 2015, 360 patients with SCD were managed (median: 7 per center; 21) of whom 137 (38%) for an ACS (median: 4 ACS per center; 8). The median length of PICU stay for ACS was 5 days (3.1). Among the 137 patients who presented with ACS, 73 (53%) received simple blood transfusion and 16 (12%) received exchange transfusion. For patients who required noninvasive ventilatory support, NIV with bilevel pressure (BiPAP) was the most frequent method (n = 68, 50%), followed by continuous positive airway pressure (CPAP) (n = 23, 17%) and high-flow oxygen (n = 21, 15%). The proportion of patients on BiPAP was up to 71% in the centers most frequently managing ACS patients.

CONCLUSION

BiPAP is commonly used in PICUs for SCD patients with ACS, especially in trained centers. Future physiological studies and randomized controlled trials might help to choose the best ventilatory support for ACS.

Red cell transfusion and alloimmunization in sickle cell disease

Red cell transfusion remains a critical component of care for acute and chronic complications of sickle cell disease. Randomized clinical trials demonstrated the benefits of transfusion therapy for prevention of primary and secondary strokes and postoperative acute chest syndrome. Transfusion for splenic sequestration, acute chest syndrome, and acute stroke are guided by expert consensus recommendations. Despite overall improvements in blood inventory safety, adverse effects of transfusion are prevalent among patients with sickle cell disease and include alloimmunization, acute and delayed hemolytic transfusion reactions, and iron overload. Judicious use of red cell transfusions, optimization of red cell antigen matching, and the use of erythrocytapheresis and iron chelation can minimize adverse effects. Early recognition and management of hemolytic transfusion reactions can avert poor clinical outcomes. In this review, we discuss transfusion methods, indications, and complications in sickle cell disease with an emphasis on alloimmunization.

Transfusion and Cellular Therapy in Pediatric Sickle Cell Disease

Red blood cell (RBC) transfusion is critical in managing acute and chronic complications of sickle cell disease. Alloimmunization and iron overload remain significant complications of transfusion therapy and are minimized with prophylactic Rh and K antigen RBC matching and iron chelation. Matched sibling donor hematopoietic stem cell transplant (HSCT) is a curative therapeutic option. Autologous hematopoietic stem cell (HSC)-based gene therapy has recently shown great promise, for which obtaining sufficient HSCs is essential for success. This article discusses RBC transfusion indications and complications, transfusion support during HSCT, and HSC mobilization and collection for autologous HSCT with gene therapy.

Hemoglobin Target and Transfusion Modality for Adult Patients With Sickle Cell Disease Acute Chest Syndrome

BACKGROUND

Despite the importance of transfusion in treating sickle cell disease acute chest syndrome, the target hemoglobin and optimal modality for transfusion remain unknown.

OBJECTIVES

To compare hospital length of stay (LOS) in intensive care unit (ICU) patients with acute chest syndrome transfused to hemoglobin ≥ 8 g/dL versus patients transfused to hemoglobin < 8 g/dL; and to compare hospital LOS in acute chest syndrome patients treated with and without exchange transfusion.

METHODS

We performed a retrospective cohort study of all acute chest syndrome patients treated in the medical ICU at 2 tertiary care hospitals between January 2011 and August 2016 (n = 82). We compared median hospital LOS in patients transfused to hemoglobin ≥ 8 g/dL by the time of ICU transfer to the medical floor versus patients transfused to hemoglobin < 8 g/dL as well as patients who received exchange transfusion versus no exchange transfusion using Wilcoxon rank-sum tests. We modeled the association between hospital LOS and hemoglobin at ICU transfer to the medical floor using multivariable log-linear regression.

RESULTS

Median hospital LOS was about half as long for patients transfused to hemoglobin ≥ 8 g/dL versus hemoglobin < 8 g/dL (8.0 versus 16.5 days, P = 0.008). There was no difference in LOS for patients treated with and without exchange transfusion. On average, a 1 g/dL increase in hemoglobin was associated with a 19.5% decrease (95% CI 10.8-28.2%) in LOS, controlling for possible confounding factors.

CONCLUSIONS

Transfusion to a hemoglobin target ≥ 8 g/dL is associated with decreased hospital LOS in patients with acute chest syndrome. There was no difference in LOS between patients who received exchange transfusion and those who did not.

Prognostic significance of hemoglobin level and autoimmune hemolytic anemia in SARS-CoV-2 infection

Higher levels of D-dimer, LDH, and ferritin, all have been associated with the poor prognosis of COVID-19. In a disease where there are acute inflammation and compromised oxygenation, we investigated the impact of initial hemoglobin (Hgb) levels at Emergency Department (ED) triage on the severity and the clinical course of COVID-19. We conducted a cross-sectional study on 601 COVID-19 patients in a COVID-19 national referral center between 13 and 27 June 2020. All adult patients presented at our hospital that required admission or hotel isolation were included in this study. Patients admitted to the intensive care unit (ICU) had a lower initial Hgb than those admitted outside the ICU (12.84 g/dL vs. 13.31 g/dL, p = 0.026) and over the course of admission; the prevalence of anemia (Hgb < 12.5 g/dL) was 65% in patients admitted to ICU, whereas it was only 43% in non-ICU patients (odds ratio of 2.464, 95% CI 1.71-3.52). Anemic ICU patients had a higher mortality compared with non-anemic ICU patients (hazard ratio = 1.88, log-rank p = 0.0104). A direct agglutination test (DAT) for all anemic patients showed that 14.7% of ICU patients and 9% of non-ICU patients had autoimmune hemolytic anemia (AIHA). AIHA patients had significantly longer length of hospital stay compared with anemic patients without AIHA (17.1 days vs. 14.08 days, p = 0.034). Lower Hgb level at hospital presentation could be a potential surrogate for COVID-19 severity.

Transfusion support in patients with sickle cell disease

Blood transfusions are an integral component of the management of acute and chronic complications of sickle cell disease. Red cells can be administered as a simple transfusion, part of a modified exchange procedure involving manual removal of autologous red cells and infusion of donor red cells, and part of an automated red cell exchange procedure using apheresis techniques. Individuals with sickle cell disease are at risk of multiple complications of blood transfusions, including transfusional hemosiderosis, auto- and alloimmunization to minor red cell and human leukocyte antigens, delayed hemolytic transfusion reactions, and hyper-hemolysis. In low- and middle-income countries in sub-Saharan Africa, where a directed donor system is prevalent and limited laboratory methods are in place to perform extended red cell phenotyping, leukodepletion of cellular products, and infectious disease screening, there are additional challenges to providing safe and adequate transfusion support for this patient population. We review current indications for acute and chronic transfusions in sickle cell disease that are derived primarily from randomized controlled trials and observational studies in children living in high-income countries. We will highlight populations with unique transfusion needs, such as pregnant women and children, as well as the role of the transfusion medicine consultative service for individuals with sickle cell disease planning to have curative hematopoietic stem cell transplantation or gene therapy. Finally, we will discuss risk factors for alloimmunization in individuals with sickle cell disease, emerging new strategies to prevent alloimmunization in this population, and critical gaps in the implementation of transfusion guidelines for sickle cell disease in high- and low-income countries.

American Society of Hematology 2020 guidelines for sickle cell disease: transfusion support

BACKGROUND

Red cell transfusions remain a mainstay of therapy for patients with sickle cell disease (SCD), but pose significant clinical challenges. Guidance for specific indications and administration of transfusion, as well as screening, prevention, and management of alloimmunization, delayed hemolytic transfusion reactions (DHTRs), and iron overload may improve outcomes.

OBJECTIVE

Our objective was to develop evidence-based guidelines to support patients, clinicians, and other healthcare professionals in their decisions about transfusion support for SCD and the management of transfusion-related complications.

METHODS

The American Society of Hematology formed a multidisciplinary panel that was balanced to minimize bias from conflicts of interest and that included a patient representative. The panel prioritized clinical questions and outcomes. The Mayo Clinic Evidence-Based Practice Research Program supported the guideline development process. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to form recommendations, which were subject to public comment.

RESULTS

The panel developed 10 recommendations focused on red cell antigen typing and matching, indications, and mode of administration (simple vs red cell exchange), as well as screening, prevention, and management of alloimmunization, DHTRs, and iron overload.

CONCLUSIONS

The majority of panel recommendations were conditional due to the paucity of direct, high-certainty evidence for outcomes of interest. Research priorities were identified, including prospective studies to understand the role of serologic vs genotypic red cell matching, the mechanism of HTRs resulting from specific alloantigens to inform therapy, the role and timing of regular transfusions during pregnancy for women, and the optimal treatment of transfusional iron overload in SCD.

Blood transfusions for treating acute chest syndrome in people with sickle cell disease

BACKGROUND

Sickle cell disease is an inherited autosomal recessive blood condition and is one of the most prevalent genetic blood diseases worldwide. Acute chest syndrome is a frequent complication of sickle cell disease, as well as a major cause of morbidity and the greatest single cause of mortality in children with sickle cell disease. Standard treatment may include intravenous hydration, oxygen as treatment for hypoxia, antibiotics to treat the infectious cause and blood transfusions may be given. This is an update of a Cochrane Review first published in 2010 and updated in 2016.

OBJECTIVES

To assess the effectiveness of blood transfusions, simple and exchange, for treating acute chest syndrome by comparing improvement in symptoms and clinical outcomes against standard care.

SEARCH METHODS

We searched The Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register, which comprises references identified from comprehensive electronic database searches and handsearching of relevant journals and abstract books of conference proceedings. Date of the most recent search: 30 May 2019.

SELECTION CRITERIA

Randomised controlled trials and quasi-randomised controlled trials comparing either simple or exchange transfusion versus standard care (no transfusion) in people with sickle cell disease suffering from acute chest syndrome.

DATA COLLECTION AND ANALYSIS

Both authors independently selected trials and assessed the risk of bias, no data could be extracted.

MAIN RESULTS

One trial was eligible for inclusion in the review. While in the multicentre trial 237 people were enrolled (169 SCC, 42 SC, 15 Sβ⁰-thalassaemia, 11Sβ+-thalassaemia); the majority were recruited to an observational arm and only ten participants met the inclusion criteria for randomisation. Of these, four were randomised to the transfusion arm and received a single transfusion of 7 to 13 mL/kg packed red blood cells, and six were randomised to standard care. None of the four participants who received packed red blood cells developed acute chest syndrome, while 33% (two participants) developed acute chest syndrome in standard care arm. No data for any pre-defined outcomes were available.

AUTHORS' CONCLUSIONS

We found only one very small randomised controlled trial; this is not enough to make any reliable conclusion to support the use of blood transfusion. Whilst there appears to be some indication that chronic blood transfusion may play a roll in reducing the incidence of acute chest syndrome in people with sickle cell disease and albeit offering transfusions may be a widely accepted clinical practice, there is currently no reliable evidence to support or refute the perceived benefits of these as treatment options; very limited information about any of the potential harms associated with these interventions or indeed guidance that can be used to aid clinical decision making. Clinicians should therefore base any treatment decisions on a combination of; their clinical experience, individual circumstances and the unique characteristics and preferences of adequately informed people with sickle cell disease who are suffering with acute chest syndrome. This review highlights the need of further high quality research to provide reliable evidence for the effectiveness of these interventions for the relief of the symptoms of acute chest syndrome in people with sickle cell disease.

Identification of Clinical and Laboratory Parameters Associated with the Development of Acute Chest Syndrome during Vaso-Occlusive Episodes in Children with Sickle Cell Disease: A Preliminary Step before Assessing Specific and Early Treatment Strategies

This prospective observational study sought to ascertain clinical and laboratory parameters associated with the development of acute chest syndrome (ACS) during vaso-occlusive episodes (VOE) in children with sickle cell disease (SCD). It was performed at the pediatric department of the university Intercommunal Créteil hospital. All children with SCD (all sickle genotypes) consecutively admitted from November 2013 to December 2016 for painful VOEs and no evidence of ACS were included. Clinical and laboratory parameters collected at admission and within 48 h after admission were compared for children in whom ACS developed or not. Variables that were statistically significant on univariate analysis or considered to be clinically relevant were included in a multivariable model to ascertain the risk factors associated with the development of ACS during a VOE. The variables retained in the multivariate model were used to construct a predictive score for ACS. For each included child and during the study period, only data from the first VOE and/or the first ACS were analyzed. Among 191 hospitalizations for painful VOEs, for 176 children with SCD, ACS developed in 35 during hospitalization. Mean hospital stay was longer for children with ACS versus VOEs alone (7.6 (±2.3) vs. 3.3 (±1.8) days, p < 0.0001), and all children with ACS versus 28/156 (17.9%) with VOEs alone received red blood cell transfusion (p < 0.0001). The multivariate model retained pain score (≥9/10), pain localization (abdominal or spinal pain or involving more than two limbs), and high reticulocyte (≥260 × 10⁹/L) and neutrophil (>10 × 10⁹/L) counts, at admission, as independently associated with ACS development. The area under the receiver operating characteristic curve for the ACS predictive score was 0.82 (95% CI: 0.74–0.89), and the negative predictive value was 97.7%. The evolution profiles during the first 48 h differed between children with ACS and VOEs alone, with a more rapid decline of pain score and leucocytosis in children with VOEs. Clinical and laboratory measurements at admission may be simple parameters to identify children with increased risk of ACS development during VOEs and to facilitate early diagnosis of this respiratory complication. Also, the persistent elevation of leukocyte count on day 2 may be considered a sign of evolving ACS.

Recommendations for the use of red blood cell exchange in sickle cell disease

Sickle cell disease (SCD) is a genetic disorder characterised by a single mutation of the beta globin gene, causing the production of an abnormal haemoglobin called sickle haemoglobin (HbS). In its deoxygenated form, HbS polymerises, causing major rheological disorders, which presents clinically as periodic vaso-occlusive crises, chronic haemolysis and chronic vascular dysfunction. Patients often resort to a background treatment, and transfusion remains the cornerstone in the management of the disease, significantly reducing morbidity and mortality. The aim of red blood cell exchange (RBCX) is to improve tissue oxygenation by increasing haemoglobin levels while lowering HbS levels. RBCX can be performed by manual or automated exchange, and each technique has its own set of advantages and disadvantages. This article will outline the transfusion indications for the main complications of SCD, as well as the most appropriate strategy to use.

Recommendations on RBC Transfusion Support in Children With Hematologic and Oncologic Diagnoses From the Pediatric Critical Care Transfusion and Anemia Expertise Initiative

OBJECTIVES

To present the recommendations and supporting evidence for RBC transfusions in critically ill children with hematologic and oncologic disease from the Pediatric Critical Care Transfusion and Anemia Expertise Initiative.

DESIGN

Consensus conference series of international, multidisciplinary experts in RBC transfusion management of critically ill children.

METHODS

The panel of 38 experts developed evidence-based and, when evidence was lacking, expert-based clinical recommendations and research priorities for RBC transfusions in critically ill children. The hematologic/oncologic subgroup included seven experts. Electronic searches were conducted using PubMed, EMBASE, and Cochrane Library databases from 1980 to May 2017. Agreement was obtained using the Research and Development/UCLA Appropriateness Method. Results were summarized using the Grading of Recommendations Assessment, Development, and Evaluation method.

RESULTS

The hematologic/oncologic subgroup developed 14 recommendations (seven clinical, seven research); all achieved greater than 80% agreement. In patients with sickle cell disease, Transfusion and Anemia Expertise Initiative recommends: 1) RBC transfusion to achieve a target hemoglobin concentration of 10 g/dL rather than hemoglobin of less than 30% prior to surgical procedures requiring general anesthesia and 2) exchange transfusion over simple (nonexchange) transfusion if the child's condition is deteriorating (based on clinical judgment), otherwise a simple, nonexchange RBC transfusion is recommended. There is insufficient evidence to make recommendations on transfusion thresholds for patients with sickle cell disease prior to minor procedures, with acute stroke or with pulmonary hypertension. For patients with oncologic disease or undergoing hematopoietic stem cell transplant, a hemoglobin concentration of 7-8 g/dL is recommended. Due to lack of evidence, research is needed to clarify the appropriate transfusion thresholds in these patients.

CONCLUSIONS

Transfusion and Anemia Expertise Initiative developed specific pediatric recommendations regarding RBC transfusion management in critically ill children with sickle cell disease, oncologic disease, and hematopoietic stem cell transplant and recommendations to help guide future research priorities.

Early Noninvasive Ventilation and Nonroutine Transfusion for Acute Chest Syndrome in Sickle Cell Disease in Children: A Descriptive Study

OBJECTIVES

To describe the need for transfusion and short- and long-term evolutions of pediatric sickle cell disease patients with acute chest syndrome for whom early continuous noninvasive ventilation represented first-line treatment.

DESIGN

Single-center retrospective chart study in PICU.

SETTING

A tertiary and quaternary referral PICU.

PATIENTS

All sickle cell disease patients 5-20 years old admitted with confirmed acute chest syndrome and not transfused in the previous month were included.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic data, laboratory and radiologic findings, transfusions, invasive ventilation, oxygen and noninvasive ventilation settings, duration of opioid treatment, length of hospital stay, and severe sickle cell disease complications in the ensuing 2 years were extracted from medical charts. Sixty-six acute chest syndrome in 48 patients were included. Continuous early noninvasive ventilation was well tolerated in 65 episodes, with positive expiratory pressure 4 cm H2O and pressure support 10 cm H2O (median) administered continuously, then discontinued during 7 days (median). No patient necessitated invasive ventilation or died. Twenty-three acute chest syndrome (35%) received transfusions; none received blood exchange. Transfused patients had more frequent upper lobe radiologic involvement, more severe anemia, higher reticulocyte counts, and higher C-reactive protein than nontransfused patients. Their evolution was more severe in terms of length of opioid requirement, length of noninvasive ventilation treatment, overall time on noninvasive ventilation, and length of stay. At 2-year follow-up after the acute chest syndrome episode, no difference was observed between the two groups.

CONCLUSIONS

Early noninvasive ventilation combined with nonroutine transfusion is well tolerated in acute chest syndrome in children and may spare transfusion in some patients. Early recognition of patients still requiring transfusion is essential and warrants further studies.

Acute Chest Syndrome in Children with Sickle Cell Disease

Acute chest syndrome (ACS) is a frequent cause of acute lung disease in children with sickle cell disease (SCD). Patients may present with ACS or may develop this complication during the course of a hospitalization for acute vaso-occlusive crises (VOC). ACS is associated with prolonged hospitalization, increased risk of respiratory failure, and the potential for developing chronic lung disease. ACS in SCD is defined as the presence of fever and/or new respiratory symptoms accompanied by the presence of a new pulmonary infiltrate on chest X-ray. The spectrum of clinical manifestations can range from mild respiratory illness to acute respiratory distress syndrome. The presence of severe hypoxemia is a useful predictor of severity and outcome. The etiology of ACS is often multifactorial. One of the proposed mechanisms involves increased adhesion of sickle red cells to pulmonary microvasculature in the presence of hypoxia. Other commonly associated etiologies include infection, pulmonary fat embolism, and infarction. Infection is a common cause in children, whereas adults usually present with pain crises. Several risk factors have been identified in children to be associated with increased incidence of ACS. These include younger age, severe SCD genotypes (SS or Sβ⁰ thalassemia), lower fetal hemoglobin concentrations, higher steady-state hemoglobin levels, higher steady-state white blood cell counts, history of asthma, and tobacco smoke exposure. Opiate overdose and resulting hypoventilation can also trigger ACS. Prompt diagnosis and management with intravenous fluids, analgesics, aggressive incentive spirometry, supplemental oxygen or respiratory support, antibiotics, and transfusion therapy, are key to the prevention of clinical deterioration. Bronchodilators should be considered if there is history of asthma or in the presence of acute bronchospasm. Treatment with hydroxyurea should be considered for prevention of recurrent episodes. This review evaluates the etiology, pathophysiology, risk factors, clinical presentation of ACS, and preventive and treatment strategies for effective management of ACS.

Sickle cell disease: when and how to transfuse

Blood transfusion remains an important therapeutic intervention in patients with sickle cell disease (SCD), aiming to both increase the oxygen carrying capacity of blood and to reduce the complications of vaso-occlusion. Simple, manual exchange and automated exchange can be effective in reducing the acute and chronic complications of SCD, and the advantages and disadvantages of each methodology mean they all have a role in different situations. Evidence for the role of emergency transfusion in the management of the acute complications of SCD, including acute pain and acute chest syndrome, comes from observational data. Several important randomized controlled trials have shown the efficacy of transfusion in primary and secondary stroke prevention in patients with SCD but, outside these areas, clinical practice lacks a clear evidence base. Evidence for the role of long-term transfusion in the prevention of the non-neurologic chronic complications of SCD comes from analysis of secondary outcomes of these randomized trials and from observational data. In view of the paucity of data, the risks and benefits of transfusion should be fully discussed with patients/families before a long-term transfusion program is commenced. Evidence is only available for the role of preoperative transfusion or for prophylactic transfusion through pregnancy in certain situations, and the role of transfusions outside these situations is discussed. Questions about when and how to transfuse in SCD remain and will need further randomized trials to provide answers.

Blood transfusions for treating acute chest syndrome in people with sickle cell disease

BACKGROUND

Sickle cell disease is an inherited autosomal recessive blood condition and is one of the most prevalent genetic blood diseases worldwide. Acute chest syndrome is a frequent complication of sickle cell disease, as well as a major cause of morbidity and the greatest single cause of mortality in children with sickle cell disease. Standard treatment may include intravenous hydration, oxygen as treatment for hypoxia, antibiotics to treat the infectious cause and blood transfusions may be given. This is an update of a Cochrane review first published in 2010.

OBJECTIVES

To assess the effectiveness of blood transfusions, simple and exchange, for treating acute chest syndrome by comparing improvement in symptoms and clinical outcomes against standard care.

SEARCH METHODS

We searched The Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register, which comprises references identified from comprehensive electronic database searches and handsearching of relevant journals and abstract books of conference proceedings.Date of the most recent search: 25 April 2016.

SELECTION CRITERIA

Randomised controlled trials and quasi-randomised controlled trials comparing either simple or exchange transfusion versus standard care (no transfusion) in people with sickle cell disease suffering from acute chest syndrome.

DATA COLLECTION AND ANALYSIS

Both authors independently selected trials and assessed the risk of bias, no data could be extracted.

MAIN RESULTS

One trial was eligible for inclusion in the review. While in the multicentre trial 237 people were enrolled (169 SCC, 42 SC, 15 Sβ⁰-thalassemia, 11Sβ(+)-thalassemia); the majority were recruited to an observational arm and only ten participants met the inclusion criteria for randomisation. Of these, four were randomised to the transfusion arm and received a single transfusion of 7 to 13 ml/kg packed red blood cells, and six were randomised to standard care. None of the four participants who received packed red blood cells developed acute chest syndrome, while 33% (two participants) developed acute chest syndrome in standard care arm. No data for any pre-defined outcomes were available.

AUTHORS' CONCLUSIONS

We found only one very small randomised controlled trial; this is not enough to make any reliable conclusion to support the use of blood transfusion. Whilst there appears to be some indication that chronic blood transfusion may play a roll in reducing the incidence of acute chest syndrome in people with sickle cell disease and albeit offering transfusions may be a widely accepted clinical practice, there is currently no reliable evidence to support or refute the perceived benefits of these as treatment options; very limited information about any of the potential harms associated with these interventions or indeed guidance that can be used to aid clinical decision making. Clinicians should therefore base any treatment decisions on a combination of; their clinical experience, individual circumstances and the unique characteristics and preferences of adequately informed people with sickle cell disease who are suffering with acute chest syndrome. This review highlights the need of further high quality research to provide reliable evidence for the effectiveness of these interventions for the relief of the symptoms of acute chest syndrome in people with sickle cell disease.

Effect of automated red cell exchanges on oxygen saturation on-air, blood parameters and length of hospitalization in sickle cell disease patients with acute chest syndrome

Background:

Red cell exchanges (RCEs) lead to improvement in tissue oxygenation and reduction in inflammatory markers in sickle cell disease (SCD) patients who present with acute chest syndrome (ACS). The aim of this study is to evaluate the effects of automated-RCE (auto-RCE) on oxygen saturation (SpO₂) on-air, blood counts, the time to correct the parameters and length of hospitalization after the exchange in SCD patients presenting with ACS.

Subjects and Methods:

This was 2 years study involving five SCD patients; the time for SpO₂ on air to increase to ≥95% and chest symptoms to resolve, postprocedure, as well as the length of in-patient hospitalization was recorded. All data were entered into Statistical Package for Social Sciences Version 20.0 (SPSS Inc., Chicago, IL, USA) computer software for analyses.

Results:

The study involved 4 (80%) hemoglobin (Hb) SS and 1 (20%) HbSC patients. The median time of SpO₂ recovery was 24 h, ranging from 6 to 96 h. About 60% (3/5) of patients achieved optimal SpO₂ within 24 h post-RCE, while discharge from intensive care unit was 24 h after auto-RCE in one patient. The Hb concentration was significantly higher, while the total white cell and absolute neutrophil counts were significantly lower at the time of resolution of symptoms, compared to before auto-RCE (P < 0.05). The average post auto-red cell transfusion symptoms duration was 105.6 (24–240) h while mean inpatient stay was 244.8 (144–456) h.

Conclusion:

Auto-RCE could reverse hypoxia in ACS within 24 h.

Acute Chest Syndrome in Sickle Cell Disease: Pathophysiology and Management

Acute chest syndrome (ACS) is defined as the development of a new pulmonary infiltrate and respiratory symptoms in a patient with sickle cell disease (SCD). One of the most serious complications of SCD, ACS is the leading cause of mortality in patients with SCD. ACS is age dependent, with children having milder disease that often is infectious. Adults often have more severe disease, with pulmonary fat embolism secondary to preceding long bone infarction frequently as a contributing factor. Rapid diagnosis and a high index of suspicion are crucial since this syndrome may have a high mortality rate. A high white blood cell count and a felling hemoglobin tend to be associated with this illness. Patients are often febrile, but may not have positive blood or sputum cultures. Appropriate therapy includes judicious fluids, close attention to respiratory care, antibiotics, and transfusion therapy. Use of the drug, hydroxyurea, has been shown to decrease the incidence of ACS. Patients with repeated episodes are at risk for the development of chronic lung disease and pulmonary hypertension. New treatment strategies such as inhibitors of cytokines and pulmonary vasodilators such as nitric oxide may reduce the high mortality of ACS.

Novel insights in the management of sickle cell disease in childhood

Sickle cell disease (SCD) is a life-threatening genetic disorder characterized by chronic hemolytic anemia, vascular injury and multiorgan dysfunctions. Over the last few decades, there have been significant improvements in SCD management in Western countries, especially in pediatric population. An early onset of prophylaxis with Penicillin and a proper treatment of the infections have increased the overall survival in childhood. Nevertheless, management of painful episodes and prevention of organ damage are still challenging and more efforts are needed to better understand the mechanisms behind the development of chronic organ damages. Hydroxyurea (Hydroxycarbamide, HU), the only medication approved as a disease-modifying agent by the United States Food and Drug Administration and the European Medicines Agency, is usually under-used, especially in developing countries. Currently, hematopoietic stem-cell transplantation is considered the only curative option, although its use is limited by lack of donors and transplant-related toxicity. SCD symptoms are similar in children and adults, but complications and systemic organ damages increase with age, leading to early mortality worldwide. Experts in comprehensive care of young patients with SCD, especially those approaching the transition age to adulthood, are missing, leading people to rely on urgent care, increasing health care utilization costs and inappropriate treatments. It would be important to establish programs of comprehensive healthcare for patients with SCD from birth to adulthood, to improve their quality and expectancy of life.

Crises in Sickle Cell Disease

In spite of significant strides in the treatment of sickle cell disease (SCD), SCD crises are still responsible for high morbidity and early mortality. While most patients initially seek care in the acute setting for a seemingly uncomplicated pain episode (pain crisis or vaso-occlusive crisis), this initial event is the primary risk factor for potentially life-threatening complications. The pathophysiological basis of these illnesses is end-organ ischemia and infarction combined with the downstream effects of hemolysis that results from red blood cell sickling. These pathological changes can occur acutely and lead to a dramatic clinical presentation, but are frequently superimposed over a milieu of chronic vasculopathy, immune dysregulation, and decreased functional reserve. In the lungs, acute chest syndrome is a particularly ominous lung injury syndrome with a complex pathogenesis and potentially devastating sequelae, but all organ systems can be affected. It is, therefore, critical to understand the SCD patients' susceptibility to acute complications and their risk factors so that they can be recognized promptly and managed effectively. Blood transfusions remain the mainstay of therapy for all severe acute crises. Recommendations and indications for the safest and most efficient implementation of transfusion strategies in the critical care setting are therefore presented and discussed, together with their pitfalls and potential future therapeutic alternatives. In particular, the importance of extended phenotypic red blood cell matching cannot be overemphasized, due to the high prevalence of severe complications from red cell alloimmunization in SCD.

Red blood cell storage duration is not associated with clinical outcomes for acute chest syndrome in children with sickle cell disease

BACKGROUND

Providers commonly transfuse sickle cell disease (SCD) patients with fresh red blood cells (RBCs) as treatment for acute chest syndrome (ACS). The objective of this study was to determine if there is an association between the storage duration of RBCs and length of hospitalization and oxygen requirement after transfusion in pediatric SCD patients with ACS.

STUDY DESIGN AND METHODS

This is a retrospective cohort study of pediatric SCD patients with ACS treated with a simple RBC transfusion over 8.5 years at a single institution. Multivariate generalized estimation equation analysis was used to identify associations between storage duration of RBCs and outcome measures.

RESULTS

A total of 234 ACS episodes in 131 subjects were included. The median storage duration of the oldest unit of transfused RBCs was 17 days (interquartile range, 11-26). The majority of ACS episodes, 77.4%, were treated with 1 unit of transfused RBCs; 20.9% received 2 units; and 1.7% received 3 or more units of RBCs. There was no association between the storage duration of the oldest unit of transfused RBCs and either duration of hospitalization or supplemental oxygen requirement after transfusion in multivariate analyses.

CONCLUSION

This retrospective study is one of the first to investigate the role of the storage lesion in children with SCD and does not support the preferential transfusion of fresh RBCs for ACS. Ultimately, a randomized controlled trial is necessary to determine whether the storage age of RBCs affects outcomes for patients with SCD and ACS.

Health-related quality of life in children with sickle cell anemia: impact of blood transfusion therapy

The completion of the Multicenter Silent Infarct Transfusion Trial demonstrated that children with pre-existing silent cerebral infarct and sickle cell anemia (SCA) who received regular blood transfusion therapy had a 58% relative risk reduction of infarct recurrence when compared to observation. However, the total benefit of blood transfusion therapy, as assessed by the parents, was not measured against the burden of monthly blood transfusion therapy. In this planned ancillary study, we tested the hypothesis that a patient centered outcome, health-related quality of life (HRQL), would be greater in participants randomly assigned to the blood transfusion therapy group than the observation group. A total of 89% (175 of 196) of the randomly allocated participants had evaluable entry and exit HRQL evaluations. The increase in Change in Health, measured as the child's health being better, was significantly greater for the transfusion group than the observation group (difference estimate = -0.54, P ≤ 0.001). This study provides the first evidence that children with SCA who received regular blood transfusion therapy felt better and had better overall HRQL than those who did not receive transfusion therapy.

Red cell exchange: special focus on sickle cell disease

The primary function of red blood cells (RBCs) is to deliver oxygen from the lungs to tissues. Tissue hypoxia occurs when the oxygen-carrying capacity of RBCs is compromised due primarily to 3 causes: (1) a reduction in circulating RBC mass, (2) an increase in circulating RBC mass, or (3) abnormal hemoglobin (Hb) that either does not sufficiently release oxygen to tissues (high-oxygen-affinity hemoglobin) or occludes the microvasculature due to deformed RBCs (sickled RBCs). To improve oxygenation in patients with reduced or increased RBC mass, RBC administration (simple transfusion) or RBC removal (RBC depletion) is performed, respectively. However, for patients with abnormal Hb, RBCs containing abnormal Hb are removed and replaced by healthy volunteer donor RBCs by red cell exchange (RCE). RCE can be performed by manual exchange or by automated exchange using a blood cell separator (erythrocytapheresis). In this review, indications for RCE in sickle cell disease using the evidence-based American Society for Apheresis categories(1) are presented and the rationale for RCE in each disorder are discussed. Simple transfusion versus RCE and manual RCE versus automated RCE are compared. Finally, this review briefly presents some of the challenges of performing erythrocytapheresis in small children and discusses various choices for central venous access during RCE.(2.)

Echocardiography-derived tricuspid regurgitant jet velocity is an important marker for the progression of sickle-cell disease

BACKGROUND

Although echocardiography-derived tricuspid regurgitant jet velocity (TRV) is associated with increased mortality in sickle-cell disease (SCD), it is unclear whether increased TRV is a marker of multiorgan disease due to systemic vasculopathy or related to increased pulmonary artery systolic pressure with episodes of multiple acute chest syndrome (ACS).

METHODS

Our study analyzed 148 consecutive patients with transthoracic echocardiography with TRV data, who came to our adult SCD Clinic at the Wake Forest Baptist Medical Center. For our analysis, we took TRV ≥ 2.5 m/s as elevated. Patients were followed on average for 9 years.

RESULTS

TRV ≥ 3 m/s was significantly associated with increased mortality (p < 0.001), thromboembolism (p < 0.001), hospitalization for ACS (p < 0.001), supraventricular arrhythmia (p = 0.028), right ventricular (RV) dilation, decreased hemoglobin and increased creatinine. Patients with a progressive increase in TRV during follow-up had increased mortality (36.7 vs. 8.6%, p = 0.007) and increased ACS (45 vs. 5.7%, p < 0.001). Death was independently associated with TRV ≥ 3 m/s (p = 0.023), ACS (p = 0.001) and increased RV basal diameter (p = 0.003).

CONCLUSIONS

TRV is an important global marker for the severity and progression of SCD, and carries a significant prognostic implication.

Cardiac iron overload in sickle-cell disease

Chronically transfused sickle cell disease (SCD) patients have lower risk of myocardial iron overload (MIO) than comparably transfused thalassemia major (TM) patients. However, cardioprotection is incomplete. We present the clinical characteristics of six patients who have prospectively developed MIO, to identify potential risk factors for cardiac iron accumulation. From 2002 to 2011, cardiac, hepatic, and pancreatic iron overload were assessed by R2 and R2 * magnetic resonance imaging techniques in 201 chronic transfused SCD patients as part of their clinical care. At the time, they developed MIO, five of six patients had been on chronic transfusion for more than 11 years; only one was on exchange transfusion. The time to MIO was correlated with reticulocyte and hemoglobin S percentages. All patients had qualitatively poor chelation compliance (<50%). All patients had serum ferritin levels >4600 ng/ml and liver iron concentration >22 mg/g. Pancreatic R2 * was >100 Hz in every patient studied (5/6). Cardiac iron rose proportionally to pancreas R2 *, with all patients having pancreas R2 *>100 Hz when cardiac iron was present. MIO had a threshold relationship with liver iron that was higher than observed in TM patients. In conclusion, MIO occurs in a small percentage of chronically transfused SCD patients and is only associated with exceptionally poor control of total body iron stores. Duration of chronic transfusion is clearly important but other factors, such as levels of effective erythropoiesis, appear to contribute to cardiac risk. Pancreas R2 * can serve as a valuable screening tool for cardiac iron in SCD patients.

Outcomes of acute chest syndrome in adult patients with sickle cell disease: predictors of mortality

Adults with sickle cell disease(SCD) are a growing population. Recent national estimates of outcomes in acute chest syndrome(ACS) among adults with SCD are lacking. We describe the incidence, outcomes and predictors of mortality in ACS in adults. We hypothesize that any need for mechanical ventilation is an independent predictor of mortality.

METHODS

We performed a retrospective analysis of the Nationwide Inpatient Sample(2004-2010),the largest all payer inpatient database in United States, to estimate the incidence and outcomes of ACS needing mechanical ventilation(MV) and exchange transfusion(ET) in patients >21 years. The effects of MV and ET on outcomes including length of stay(LOS) and in-hospital mortality(IHM) were examined using multivariable linear and logistic regression models respectively. The effects of age, sex, race, type of sickle cell crisis, race, co-morbid burden, insurance status, type of admission, and hospital characteristics were adjusted in the regression models.

RESULTS

Of the 24,699 hospitalizations, 4.6% needed MV(2.7% for <96 hours, 1.9% for ≥96 hours), 6% had ET, with a mean length of stay(LOS) of 7.8 days and an in-hospital mortality rate(IHM) of 1.6%. There was a gradual yearly increase in ACS hospitalizations that needed MV(2.6% in 2004 to 5.8% in 2010). Hb-SS disease was the phenotype in 84.3% of all hospitalizations. After adjusting for a multitude of patient and hospital related factors, patients who had MV for <96 hours(OR = 67.53,p<0.01) or those who had MV for ≥96 hours(OR = 8.73,p<0.01) were associated with a significantly higher odds for IHM when compared to their counterparts. Patients who had MV for ≥96 hours and those who had ET had a significantly longer LOS in-hospitals(p<0.001).

CONCLUSION

In this large cohort of hospitalized adults with SCD patients with ACS, the need for mechanical ventilation predicted higher mortality rates and increased hospital resource utilization. Identification of risk factors may enable optimization of outcomes.

Hypoxemia in sickle cell disease: significance and management

Hypoxemia is common in SCD and likely exacerbates SCD vasculopathy. Pulse oximeter correlation with arterial oxygen tension in patients with SCD may at times be poor and arterial blood gas confirmation is required in hypoxic patients. Supplemental oxygen should be administered for the correction of hypoxemia, which if untreated creates a risk of multi-organ failure. Transfusion and hydroxyurea can improve oxygen delivery to tissues and organs. The role of supplemental oxygen therapy in preventing or reversing SCD vasculopathy is controversial. Nitric oxide therapy for VOC pain has not fulfilled promise to date. On the other hand, lung distension (CPAP, incentive spirometry, PEP therapy) are promising treatments requiring further study.

Comparison of automated red cell exchange transfusion and simple transfusion for the treatment of children with sickle cell disease acute chest syndrome

BACKGROUND

Both simple transfusion (ST) of packed red blood cells and automated red cell exchange (RCE) are used in the treatment of acute chest syndrome (ACS). We report our experience using each of these modalities for the treatment of ACS.

METHODS

Retrospective chart review of patients with ACS treated with ST only (51 episodes, ST group) or RCE performed either at diagnosis (U-RCE group, 15 episodes) or after ST (ST + RCE group, 15 episodes).

RESULTS

The mean clinical respiratory score (CRS) at diagnosis was significantly higher in the U-RCE group than in the ST group, but there were no significant differences among the other groups. The CRS and WBC each decreased significantly after simple transfusion in the ST group and after RCE in the U-RCE group, but both the CRS and WBC increased significantly, and the mean platelet count fell significantly, after simple transfusion in the ST + RCE group. Only patients in the ST + RCE group required mechanical ventilation. There were no significant differences in length of stay (LOS) or total hospital charges among any of the groups, probably due to the small sample size.

CONCLUSIONS

We conclude that the CRS identifies the patients who are most severely affected with ACS, and that upfront RCE is a safe and effective treatment for these patients. Additional work is needed to develop a method to predict which of the apparently less severely affected patients will fail to improve after simple transfusion and should receive upfront RCE.

Transfusion therapy for sickle cell disease: a balancing act

Transfusion therapy is a key intervention in decreasing morbidity and mortality in patients with sickle cell disease (SCD). Current indications for acute and chronic transfusion therapy have significantly increased the number of RBC units transfused to patients with SCD worldwide. This review summarizes transfusion management for the treatment or prevention of neurologic and perioperative complications, acute chest syndrome, and acute anemia associated with SCD. Despite the recognized benefits of transfusion therapy, it is not without the risks of iron overload, alloimmunization, and delayed hemolytic transfusion reactions. Transfusional iron overload management includes automated RBC exchange, noninvasive imaging to monitor iron burden, and iron chelation with parenteral or oral agents. Although limited and extended RBC antigen matching reduces antibody formation, the prevalence of RBC alloimmunization in patients with SCD remains high. Recent studies demonstrate that RH genetic diversity in patients with SCD contributes to Rh alloimmunization, suggesting that even more refined RBC matching strategies are needed. Advances in molecular blood group typing offer new opportunities to improve RBC matching of donors and recipients and can be of particular benefit to patients with SCD.

Indications and complications of transfusions in sickle cell disease

Red cell transfusion remains an important part of the management of acute and chronic complications in SCD. The ongoing and emerging uses of transfusions in SCD may have significant benefits; however, the potential complications of transfusions also deserve careful consideration. In this report we review current indications for transfusions, transfusion complications, modifications of transfusion practices to mitigate risk, and potential considerations to improve transfusion outcomes.

Red blood cell alloimmunization in sickle cell disease: prevalence in 2010

BACKGROUND

Transfusion of red blood cells (RBCs) is frequently required for care of individuals with sickle cell disease (SCD). Alloimmunization rates are high and may be reduced by matching for RBC antigens that can cause alloimmunization.

STUDY DESIGN AND METHODS

During the PROACTIVE Feasibility Study, patients with SCD age 2 years or older admitted for pain without acute chest syndrome were enrolled for possible randomization to preventive blood transfusion or standard care. Transfusion and antibody histories were obtained at each site, and antibody screening was done, to assess transfusion burden and alloimmunization prevalence. Participating sites were surveyed regarding antigen matching practice.

RESULTS

A total of 237 patients (169 SS, 42 SC, 15 Sβ(0) -thalassemia, 11 Sβ(+) -thalassemia), 118 males and 119 females, were enrolled. Mean age was 19.3 years (range, 2.0-68.0); there were 122 children and 115 adults. A total of 75.8% had received at least a single transfusion of RBCs before the study. Thirty-four patients (14.4%) had a history of at least one alloantibody and 17 of these had more than one. When surveyed, 19 sites (83% of responders) reported antigen matching to at least include C, E, and K for transfusion of all patients with SCD.

CONCLUSION

Though antigen typing before transfusion of people with SCD and providing antigen-negative units is now widely employed by sickle cell centers, the alloimmunization rate remains quite high in contemporary sickle cell populations and may be due in large part to transfusions received at institutions not providing extended matching.

Exchange transfusion therapy and its effects on real-time microcirculation in pediatric sickle cell anemia patients: an intravital microscopy study

Periodic blood exchange transfusion is a treatment modality commonly used to manage pediatric sickle cell anemia at the University of California Davis Medical Center. The goal of exchange transfusion therapy is to ameliorate vasoocclusion and improve tissue perfusion by removing sickled red blood cells and introducing normal red blood cells. Using computer-assisted intravital microscopy, pretransfusion and posttransfusion microvascular characteristics were analyzed. In this study, the bulbar conjunctiva exhibited a "blanched" avascular appearance in all 6 pediatric sickle cell anemia patients before transfusion, indicative of tissue hypoperfusion and ischemia. Immediately after transfusion, substantial improvement in vascularization and tissue perfusion resulted, reflected by the enhanced appearance of capillaries and arterioles. In addition, a decrease in red cell velocity was observed. These observations provide evidence that exchange transfusion therapy is beneficial in ameliorating vasoocclusion and improving tissue perfusion. However, with the paradoxical posttransfusion decrease in red cell velocity presumably due to induced hyperviscosity from the large transfusion volume, blood flow is still impaired. This decreased velocity may thwart efforts to improve oxygen delivery through transfusion and may, to some extent, promote vasoocclusion instead. This paradoxical result warrants further investigation on the effects of transfusion volume and viscosity in the exchange transfusion process.