Delayed adverse vascular events after splenectomy in hereditary spherocytosis

Pulmonary hypertension associated with chronic hemolytic anemia and other blood disorders

Pulmonary hypertension (PH) has emerged as a major complication of several hematologic disorders, including hemoglobinopathies, red cell membrane disorders, chronic myeloproliferative disorders, and splenectomy. With the exception of sickle cell disease, there are a limited number of studies systematically evaluating the prevalence of PH using the gold standard right heart catheterization in these disorders. The cause of the PH in patients with hematologic disorders is multifactorial, and a thorough diagnostic evaluation is essential. More importantly, there are virtually no high-quality data on the safety and efficacy of PH-targeted therapy in this patient population.

Altered red cell and platelet adhesion in hemolytic diseases: Hereditary spherocytosis, paroxysmal nocturnal hemoglobinuria and sickle cell disease

OBJECTIVES

Intravascular hemolysis may have important pathophysiological consequences, such as the induction of cellular adhesion and vasculopathy. We compared the adhesive properties of red cells (RBC) and platelets in hereditary spherocytosis (HS), paroxysmal nocturnal hemoglobinuria (PNH) and sickle cell disease (SCD) patients.

DESIGN AND METHODS

The adhesion of RBC and platelets, from patients and healthy subjects, was determined using static adhesion assays. RBC surface markers were characterized by flow cytometry and lactate dehydrogenase (LDH), plasma hemoglobin (pHb) and TNF-α were assayed in serum/plasma samples.

RESULTS

pHb levels were elevated in all three hemolytic diseases, indicating the incidence of intravascular hemolysis. RBC adhesion and TNF-α were augmented in HS and SCD, but not in PNH. Reticulocyte counts were raised in the three diseases, but were higher in HS and SCD than in PNH; high expressions of CD71, CD36 and CD49d were observed on SCD RBC, while CD71 alone was increased on HS and PNH RBC. Splenectomy was associated with reversals of increased pHb, RBC adhesion, reticulocytes, RBC marker expression and inflammation in HS. In contrast, platelet adhesion was elevated in SCD and PNH, but not HS. Platelet adhesion correlated significantly with serum LDH, but not pHb, in the hemolytic disease cohort; interestingly, LDH did not correlate with reticulocytes or pHb levels.

CONCLUSIONS

Results indicate that extravascular, rather than intravascular, hemolysis (and ensuing RBC production) may contribute to elevations in RBC adhesive properties in HS and SCD, while mechanisms peculiar to each disease may augment platelet adhesion in SCD and PNH.

Sickle cell disease and venous thromboembolism: what the anticoagulation expert needs to know

Venous thromboembolism (VTE) is common in patients with sickle cell disease (SCD). The etiology of increased risk of VTE in SCD patients is multifactorial and is related to both traditional factors and SCD-specific factors. Traditional risk factors such as central venous catheters, frequent hospitalization, orthopedic surgeries for avascular necrosis, and pregnancy may lead to increased incidence of VTE in the SCD population. In addition, SCD itself appears to be a hypercoagulable state, and many SCD-specific factors such as thrombophilic defects, genotype and splenectomy may modify the risk of VTE. SCD complications such as acute chest syndrome and pulmonary hypertension may also be related to VTE. Anticoagulation experts should be aware of these factors to help inform prophylaxis and treatment decisions.

Splenectomy in children with "mild" hereditary spherocytosis

Splenectomy is considered the treatment of choice for patients with "symptomatic" hereditary spherocytosis (HS). Published guidelines offering recommendations for splenectomy in HS categorize patients primarily based on hemoglobin concentration. We performed a retrospective review of 64 children having splenectomy for HS at Children's Medical Center Dallas. On the basis of hemoglobin concentration alone, 16 children (25%) had mild, 38 (59%) moderate, and 10 (16%) severe HS. However, when reticulocyte count was used to categorize disease severity, only 3 patients (5%) having splenectomy would be considered mild, 17 (27%) moderate, and 42 (66%) severe. Despite otherwise having "mild" disease defined by near-normal hemoglobin levels, many children with nontraditional or subjective signs and symptoms related to hemolytic rate received a splenectomy, and, therefore, reticulocyte count might be a more reliable laboratory marker suggesting consideration of splenectomy. A validated assessment tool incorporating quality of life indicators in addition to the traditional medical indications for splenectomy in HS would be valuable in assessing indications for the procedure.

A novel hemoglobin-binding peptide reduces cell-free hemoglobin in murine hemolytic anemia

Hemolysis can saturate the hemoglobin (Hb)/heme scavenging system, resulting in increased circulating cell-free Hb (CF-Hb) in hereditary and acquired hemolytic disease. While recent studies have suggested a central role for intravascular hemolysis and CF-Hb in the development of vascular dysfunction, this concept has stimulated considerable debate. This highlights the importance of determining the contribution of CF-Hb to vascular complications associated with hemolysis. Therefore, a novel Hb-binding peptide was synthesized and linked to a small fragment of apolipoprotein E (amino acids 141-150) to facilitate endocytic clearance. Plasma clearance of hE-Hb-b10 displayed a rapid phase t(1/2) of 16 min and slow phase t(1/2) of 10 h, trafficking primarily through the liver. Peptide hE-Hb-B10 decreased CF-Hb in mice treated with phenylhydrazine, a model of acute hemolysis. Administration of hE-Hb-B10 also attenuated CF-Hb in two models of chronic hemolysis: Berkeley sickle cell disease (SS) mice and mice with severe hereditary spherocytosis (HS). The hemolytic rate was unaltered in either chronic hemolysis model, supporting the conclusion that hE-Hb-B10 promotes CF-Hb clearance without affecting erythrocyte lysis. Interestingly, hE-Hb-B10 also decreased plasma ALT activity in SS and HS mice. Although acetylcholine-mediated facialis artery vasodilation was not improved by hE-Hb-B10 treatment, the peptide shifted vascular response in favor of NO-dependent vasodilation in SS mice. Taken together, these data demonstrate that hE-Hb-B10 decreases CF-Hb with a concomitant reduction in liver injury and changes in vascular response. Therefore, hE-Hb-B10 can be used to investigate the different roles of CF-Hb in hemolytic pathology and may have therapeutic benefit in the treatment of CF-Hb-mediated tissue damage.

Comparative effectiveness of different types of splenectomy for children with congenital hemolytic anemias

OBJECTIVE

To compare the effectiveness of different types of splenectomy in children with congenital hemolytic anemias.

STUDY DESIGN

We constructed key questions that addressed outcomes relevant to clinicians and families on effects of partial or total splenectomy, including hematologic effect, splenic function, and the risk of adverse events. We identified from Pubmed and Embase 703 studies that evaluated different types of splenectomy and accepted 93 studies that satisfied entry criteria. We graded the quality of each report and summarized the overall strength of research evidence for each key question.

RESULTS

We did not identify any randomized clinical trials. All types of splenectomy have favorable clinical outcomes in most diseases. We did not identify any hematologic advantage of laparoscopy compared with laparotomy. Adverse events are uncommon in most studies and are minimized with use of laparoscopy.

CONCLUSIONS

There is a need for randomized clinical trials and improved data collection of different types of splenectomy in congenital hemolytic anemias. Outcomes studied should address the concerns of families and clinicians to assess the risks and benefits of various treatments.

Pulmonary complications of sickle cell disease

Sickle cell disease (SCD) is a common monogenetic disorder with high associated morbidity and mortality. The pulmonary complications of SCD are of particular importance, as acute chest syndrome and pulmonary hypertension have the highest associated mortality rates within this population. This article reviews the pathophysiology, diagnosis, and treatment of clinically significant pulmonary manifestations of SCD, including acute chest syndrome, asthma, and pulmonary hypertension in adult and pediatric patients. Clinicians should be vigilant in screening and treating such comorbidities to improve patient outcomes.

Priapism in sickle-cell disease: a hematologist's perspective

INTRODUCTION

Priapism is a familiar problem to hematologists, well known for its association with sickle-cell disease (SCD). It also occurs in a variety of other hematological illnesses, nearly all forms of congenital hemolytic anemia, including other hemoglobinopathies and red blood cell membranopathies and enzymopathies.

AIM

Provide urologists with a comprehensive review of priapism in SCD, with an emphasis on the perspective of a practicing hematologist.

METHODS

Medline searches through July 2010 were conducted using the terms priapism, erectile dysfunction, and sickle cell.

MAIN OUTCOME MEASURES

Expert opinion was based on review of the medical literature related to this subject matter.

RESULTS

In men with SCD, large epidemiological studies have linked the risk of priapism to clinical markers of the severity of intravascular hemolysis. Extracellular hemoglobin and arginase released during hemolysis has been implicated in reducing nitric oxide bioavailability, although the relevance of hemolysis to vascular dysfunction has been challenged by some scientists. Consistent with the role of impairment of the nitric oxide axis, mice genetically deficient in nitric oxide production have also been shown to develop priapic activity. Provocative new data indicate that hemolysis-linked dysregulation of adenosine signaling in the penis contributes to priapism in sickle cell mice. Serious questions have arisen regarding the efficacy of mainstays of textbook dogma for treatment of acute severe priapism, including intravenous fluids, alkalinization, and exchange transfusion, and there is increasing acceptance for early aspiration and irrigation of the corpus cavernosum.

CONCLUSION

For patients with sickle cell with recurrent priapism, there is very limited evidence for a medical prophylaxis role for hydroxyurea, etilefrine, pseudoephedrine, leuprolide, sildenafil, and other agents. Recent publications have highlighted nitric oxide and adenosine signal transduction pathways as worthy of additional research. Research and clinical management of sickle-cell priapism is strengthened by multidisciplinary collaboration between hematologists and urologists.

Increased eosinophilic responses in splenectomized patients

BACKGROUND

The spleen is a key organ within the immune system. Its removal is known to bring about adverse effects such as an increased susceptibility to overwhelming infection. Few reports have suggested that the spleen may play a role in controlling eosinophilic responses, mostly based on animal models.

OBJECTIVES

To examine whether the human spleen impacts eosinophil numbers in the blood.

METHODS

We have retrospectively analyzed eosinophil counts and medical records of 29 patients who had undergone splenectomy between 2000 and 2010. Statistical comparison was performed between post-splenectomy blood counts and both pre-splenectomy and control values. Data regarding the clinical settings around hypereosinophilia events were obtained from patient charts.

RESULTS

An increased rate of eosinophilia was observed after splenectomy as compared with normal individuals. Furthermore, a considerable proportion of patients who had undergone splenectomies (8/29) presented peak eosinophil numbers exceeding 1,000/mm(3), reaching a maximum of 3,070/mm(3). These values were mostly encountered perioperatively or during episodes of acute infection.

CONCLUSIONS

Our data indicate that impaired control of eosinophilic responses is a long-term post-splenectomy effect and is evident in the context of acute stress. We suggest that the spleen plays a significant role in controlling eosinophil levels and that these cells may mediate some of the harmful consequences observed after removal of the spleen.

Guidelines for the diagnosis and management of hereditary spherocytosis--2011 update

Guidelines on hereditary spherocytosis (HS) published in 2004 (Bolton-Maggs et al, 2004) are here replaced to reflect changes in current opinion on the surgical management, (particularly the indications for concomitant splenectomy with cholecystectomy in children with mild HS, and concomitant cholecystectomy with splenectomy in those with asymptomatic gallstones). Further potential long term hazards of splenectomy are now recognised. Advances have been made in our understanding of the biochemistry of the red cell membrane which underpins the choice of tests. Biochemical assays of membranes proteins and genetic analysis may be indicated (rarely) to diagnose atypical cases. The diagnostic value of the eosin-5-maleimide (EMA) binding test has been validated in a number of studies with understanding of its limitations.

Partial splenectomy for hereditary spherocytosis: a multi-institutional review

BACKGROUND/PURPOSE

Partial splenectomy has emerged as a surgical option for selected children with hereditary spherocytosis, with the goal of reducing anemia while preserving splenic function. This multi-institutional study is the largest series to date examining outcomes data for partial splenectomy in patients with hereditary spherocytosis.

METHODS

Data were collected retrospectively from 5 North American pediatric hospitals. Sixty-two children underwent partial splenectomy for hereditary spherocytosis between 1990 and 2008.

RESULTS

At 1 year following partial splenectomy, mean hemoglobin significantly increased by 3.0 ± 1.4 g/dL (n = 52), reticulocyte count decreased by 6.6% ± 6.6% (n = 41), and bilirubin level decreased by 1.3 ± 0.9 mg/dL (n = 25). Patients with poor or transient hematologic response were found to have significantly more splenic regeneration postoperatively compared with patients with a durable clinical response (maximal spleen dimension, 9.0 ± 3.4 vs 6.3 ± 2.2 cm). Clinically significant recurrence of anemia or abdominal pain led to completion splenectomy in 4.84% of patients. No patients developed postsplenectomy sepsis.

CONCLUSIONS

Our multi-institutional review indicates that partial splenectomy for hereditary spherocytosis leads to sustained and clinically significant improvement in hematologic profiles and clinical symptoms in most patients. Our data support partial splenectomy as an alternative for selected children with hereditary spherocytosis.

Traditional laboratory measures of cardiovascular risk in hereditary spherocytosis

BACKGROUND

Individuals who have undergone splenectomy may be at an increased risk of arterial and venous thrombosis. We sought to determine if splenectomy affects surrogate laboratory measures of cardiovascular risk in persons with hereditary spherocytosis (HS).

PROCEDURE

We conducted a prospective cross-sectional study of 21 children and 36 adults with HS. Fasting blood samples were collected for complete blood count and plasma lipid panel, homocysteine, lipoprotein (a), C-reactive protein, and fibrinogen. The variables were compared between the groups with and without prior splenectomy by Mann-Whitney tests.

RESULTS

Subjects with prior splenectomy had higher hemoglobin, white blood cell and platelet counts and lower reticulocyte counts and total serum bilirubin concentrations (P < 0.001). Subjects not having had splenectomy had lower than normal levels of total and LDL-cholesterol (LDL-C). Total and LDL-C values were significantly higher, as were fibrinogen and homocysteine concentrations, in the post-splenectomy subjects than in individuals with intact spleen.

CONCLUSION

Various lipid levels and other measures of cardiovascular risk are affected by splenectomy in persons with HS. Further investigations are indicated to more clearly define the balance of the potential benefits of hemolysis and anemia versus the deleterious effects of splenectomy in HS.

Chronic immune thrombocytopenic purpura-who needs medication?

Chronic ITP (immune thrombocytopenic purpura; now defined as duration of more than 12 months) is not always associated with significant bleeding problems so that most children and adults can be managed expectantly with no medication unless surgery, accidents or other pathology mandate it. A cut-off platelet count of 30 x 10(9)/l divides a group with no increased mortality from those whose risk is greater and in whom medication is usually appropriate. There is increasing recognition of long-term morbidity and mortality associated with immune suppression induced by medication and more recently new concerns have arisen about the long-term vascular complications of splenectomy. A more conservative approach to medication is warranted in many patients with chronic ITP.

Pleiotropic effects of intravascular haemolysis on vascular homeostasis

The breakdown of senescent or defective red blood cells releases red cell contents, especially haemoglobin, which scavenges nitric oxide (NO) and decomposes to haem and free iron. These are potent oxidants, all of which have promoted the evolution of inducible and vasculoprotective compensatory pathways to rapidly clear and detoxify haemoglobin, haem and iron. Chronic haemolytic red cell disorders as diverse as sickle cell disease, thalassaemia, unstable haemoglobinopathy, cytoskeletal defects and enzymopathies have been linked to a clinical constellation of pulmonary hypertension, priapism, leg ulceration and possibly cerebrovascular disease and thrombosis. Besides free haemoglobin, haemolysis has been associated with extracellular arginase that limits substrate availability to NO synthase, endogenous inhibitors of NO synthase activity, and inappropriate activation of haemostatic pathways. This article reviews the haemolytic disorders that have been reported to manifest vascular complications, and explores the speculative possibility that haemolysis mediates some of the vascular complications of inflammation and diabetes.

Vascular complications after splenectomy for hematologic disorders

The most widely recognized long-term risk of splenectomy is overwhelming bacterial infection. More recently, thrombosis has become appreciated as another potential complication of the procedure. Because of these long-term risks, the indications for and timing of splenectomy are debated in the medical community. Accordingly, the adverse effects and benefits of splenectomy for hematologic disorders and other conditions demand further study. This comprehensive review summarizes the existing literature pertaining to vascular complications after splenectomy for hematologic conditions and attempts to define the potential pathophysiologic mechanisms involved. This complex topic encompasses diverse underlying conditions for which splenectomy is performed, diverse thrombotic complications, and multiple pathophysiologic mechanisms.