Current obstetric outcomes in Jamaican women with sickle hemoglobinopathy - a balance of risks for aspirin?

OBJECTIVES

Sickle cell disease (SCD) occurs in 2.8 % of our Jamaican antenatal population with homozygous HbSS being most associated with adverse maternal and perinatal outcomes.

METHODS

A retrospective comparative analysis of HbSS, HbSC and HbSβThal pregnancy outcomes at the University Hospital of the West Indies (UHWI) between January 2012 and December 2022 was conducted.

RESULTS

Of 120 patients (138 pregnancies), obesity occurred in 36 % (20/56) of the 'non-HbSS' group, i.e. HbSβThal (55 %, 5/9) and HbSC (32 %, 15/47) combined vs. 9.7 % of the HbSS (8/82). HbSS patients had more crises requiring transfusions, acute chest syndrome (ACS), maternal 'near-misses' (OR=10.7, 95 % 3.5-32.3; p<0.001), hospitalizations (OR 7.6, 95 % CI 3.4-16.9; p<0.001), low birth weight (LBW) neonates (OR 3.1, 1.1-8.9; p=0.037) and preterm birth (OR=2.6, 1.2-5.8; p=0.018) compared to HbSC and HbSβThal. Low dose aspirin was prescribed in 43 %. Logistic regression showed those NOT on aspirin (n=76) had more miscarriages (22 v. 2 %), were LESS likely to have a live birth (75 v. 95 % (0.2, 0.04-0.57, p=0.005)), but surprisingly had fewer painful crises (28 v. 46 % (0.5, 0.03-0.9, p=0.03)).

CONCLUSIONS

HbSS women had a 10-fold excess of maternal near-misses. Additional research may further clarify the effects of aspirin on pregnancy outcomes as related to SCD genotypes.

Cerebrovascular disease in sickle cell disease

Sickle cell disease (SCD) is the most common type of hereditary anaemia and genetic disorder worldwide. Cerebrovascular disease is one of its most devastating complications, with consequent increased morbidity and mortality. Current guidelines suggest that children and adults with SCD who develop acute ischaemic stroke should be transfused without delay. Those with acute ischaemic stroke aged over 18 years who present within 4.5 hours of symptom onset should be considered for intravenous thrombolysis; older patients with conventional vascular risk factors are the most likely to benefit. Endovascular thrombectomy should be considered carefully in adults with SCD as there are few data to guide how the prevalence of cerebral vasculopathy may confound the expected benefits or risks of intervention. We present a practical approach to cerebrovascular disease in sickle cell patients based on the available evidence and our experience.

Characteristics and outcomes of stroke hospitalizations in patients with sickle cell disease and moyamoya syndrome

OBJECTIVES

Stroke is the leading cause of death in patients with Sickle cell disease (SCD). Here, we detail the burden of Moyamoya syndrome (MMS) as a cause of stroke in patients with SCD.

MATERIALS AND METHODS

A review of SCD-related hospital discharges was conducted utilizing the National Inpatient Sample. Rates of stroke hospitalization, risk factors, procedures, and outcomes were compared between patients with SCD-MMS and SCD alone. Univariate analyses including T-test, Wilcoxon Rank-Sum test, Chi-square were performed to compare risk factors and outcomes. Multivariable regression was used to identify predictors of stroke unique to each population.

RESULTS

Stroke occurred in 9.8% of SCD-MMS hospitalizations versus 0.5% of those involving patients with SCD alone (OR = 20.71, p < 0.001). Patients with SCD-MMS developed stroke at younger ages and with fewer comorbidities compared to those with SCD alone. Stroke hospitalizations in SCD-MMS involved a greater number of procedures (90.5% vs. 79.3%, p = 0.007), but were more likely to result in favorable discharge (58.5% vs. 44.2%, p = 0.005). The presence of anemia during hospitalization was a significant risk factor for stroke in both cohorts. Long-term antiplatelet use was protective against stroke (OR = 0.42, p = 0.008) only in the SCD-MMS cohort.

CONCLUSIONS

MMS confers a 20-fold increased risk of stroke among patients with SCD and appears to be an important cause of recurrent stroke in this population. Anemia is one of the most significant risk factors for stroke, while antiplatelet use appears to confer a protective benefit.

Sulfated non-anticoagulant heparin derivative modifies intracellular hemoglobin, inhibits cell sickling in vitro, and prolongs survival of sickle cell mice under hypoxia

Sickle cell disease (SCD) is an autosomal recessive genetic disease caused by a single point mutation, resulting in abnormal sickle hemoglobin (HbS). During hypoxia or dehydration, HbS polymerizes to form insoluble aggregates and induces sickling of red blood cells, which increases the adhesiveness of the cells, thereby altering the rheological properties of the blood, and triggers inflammatory responses, leading to hemolysis and vaso-occlusive crises. Unfractionated heparin and low-molecular weight heparins have been suggested as treatments to relieve coagulation complications in SCD. However, they are associated with bleeding complications after repeated dosing. An alternative sulfated non-anticoagulant heparin derivative (S-NACH) was previously reported to have no to low systemic anticoagulant activity and no bleeding side effects, and it interfered with P-selectin-dependent binding of sickle cells to endothelial cells, with concomitant decrease in the levels of adhesion biomarkers in SCD mice. S-NACH has been further engineered and structurally enhanced to bind with and modify HbS to inhibit sickling directly, thus employing a multimodal approach. Here, we show that S-NACH can: (i) directly engage in Schiff-base reactions with HbS to decrease red blood cell sickling under both normoxia and hypoxia in vitro, (ii) prolong the survival of SCD mice under hypoxia, and (iii) regulate the altered steady state levels of pro- and anti-inflammatory cytokines. Thus, our proof-of-concept, in vitro and in vivo preclinical studies demonstrate that the multimodal S-NACH is a highly promising candidate for development into an improved and optimized alternative to low-molecular weight heparins for the treatment of patients with SCD.

Hemoglobin SE Disease Presenting as a High-Altitude Massive Splenic Infarction Complicated by Hemorrhagic Conversion and Splenectomy

Hemoglobin SE (HbSE) disease is a hemoglobinopathy resulting from the combination of hemoglobin S (HbS) and hemoglobin E (HbE) genotypes. It may present as a vaso-occlusive crisis (VOC) in the setting of an acute stressor. Herein, we present a case of undiagnosed HbSE disease presenting as a massive splenic infarct in the setting of high-altitude exposure. A 55-year-old female of South Asian descent presented with acute left upper quadrant abdominal pain after hiking in the Swiss Alps four days previously. Laboratory testing revealed that she had hemolytic anemia, and computed tomography (CT) imaging showed a greater than 50% splenic infarction. After the initiation of anticoagulation, she experienced a hemorrhagic conversion of the initial splenic infarct resulting in acute hemodynamic decompensation. She initially underwent vascular intervention with arterial plugging, coiling, and embolization but ultimately required a splenectomy and partial colectomy upon developing a large splenic hematoma. Hemoglobin electrophoresis was consistent with hemoglobin SE disease. Hemoglobin variants, especially combined heterozygosity, are rare and have the potential to present as a vaso-occlusive crisis in the setting of acute chemical and physiological stresses. Only 43 cases of hemoglobin SE disease have been previously reported and one other occurrence in the setting of high altitude. Conservative management is recommended when a diagnosis of sickle cell trait (SCT) is definite, in comparison with cardioembolic phenomena, in which antiplatelet and anticoagulant therapy should be initiated. Hemoglobin SE disease is a rare heterozygous hemoglobinopathy resulting from the combination of hemoglobin variants geographically separated by thousands of miles. Currently, there are no strict guidelines supporting anticoagulation for the management of VOC in hemoglobinopathies. Splenic infarct in HbSE disease should be managed similarly to SCT/sickle cell disease (SCD) with fluids and analgesia, and anticoagulation should be limited to confirmed thromboembolic events and with the insight of an anticoagulant specialist.

Sickle Cell Disease and Stroke

Cerebral infarction is a common complication of sickle cell disease and may manifest as overt stroke or cognitive impairment associated with "silent" cerebral infarction on magnetic resonance imaging. Vasculopathy may be diagnosed on transcranial Doppler or magnetic resonance angiography. The risk factors in sickle cell disease for cognitive impairment, overt ischemic stroke, silent cerebral infarction, overt hemorrhagic stroke, and vasculopathy defined by transcranial Doppler or magnetic resonance angiography overlap, with severe acute and chronic anemia, acute chest crisis, reticulocytosis, and low oxygen saturation reported with the majority. However, there are differences reported in different cohorts, which may reflect age, geographic location, or neuroimaging techniques, for example, magnetic resonance imaging field strength. Regular blood transfusion reduces, but does not abolish, the risk of neurological complications in children with sickle cell disease and either previous overt stroke or silent cerebral infarction or abnormal transcranial Doppler. There are relatively few data on the use of hydroxyurea or other management strategies. Early assessment of the risk of neurocognitive complications is likely to become increasingly important in the management of sickle cell disease.

Sickle cell disease is associated with higher mortality among patients hospitalized with ischemic bowel disease

BACKGROUND

Sickle cell disease (SCD) is the most common inheritable hematologic disorder in the USA and is associated with ischemic organ diseases. SCD-associated ischemic bowel disease is increasing being recognized, and studies on the hospitalization outcomes of such patients are limited.

OBJECTIVE

This study aimed to compare the inpatient outcomes of ischemic bowel disease among patients with SCD compared with patients without SCD.

MATERIALS AND METHODS

This is a case-control study using data from the National Inpatient Sample Database (2007-2014). We analyzed and compared outcomes between cases (ischemic bowel disease with SCD) and controls (ischemic bowel disease without SCD), matched in a 1 : 5 ratio. The primary outcome was in-hospital mortality, and the secondary outcomes were healthcare resource utilization including mechanical ventilation, hemodialysis, transfusion, length of stay, and hospital charges.

RESULTS

Of the 194 262 patients admitted with ischemic bowel disease, 98 had a diagnosis of SCD and were matched successfully to the controls. In multivariate analysis, patients with SCD had twice the mortality odds of those without (adjusted odds ratio=2.06, 95% confidence intervals: 1.13-3.74). They were more likely to require mechanical ventilation and blood transfusion, and to be discharged to secondary health facilities [1.68 (1.02-2.76), 3.32 (2.15-5.12), and 1.84 (1.02-3.35)]. Patients with SCD also had a higher frequency of pneumonia, acute respiratory failure, and hemodialysis for acute renal failure. There was no significant difference in the length of stay or the total hospital charge between the two groups.

CONCLUSION

In patients hospitalized with ischemic bowel disease, SCD is associated with significantly increased mortality and healthcare burden.

A Scientific Renaissance: Novel Drugs in Sickle Cell Disease

We have entered an era of exploding interest in therapeutics for sickle cell disease. The expansion in our understanding of sickle cell disease pathophysiology has enhanced the range of potential therapeutic targets. From induction of fetal hemoglobin to antiadhesion molecules, we are potentially on the cusp of making life-altering modifications for individuals with sickle cell disease. This disease population cannot afford to let the current momentum wane. Studies exploring combinations of therapies affecting multiple steps in the pathophysiology and exploring novel and clinically relevant outcomes are incumbent.

Comparison of Outcomes in Patients Having Acute Myocardial Infarction With Versus Without Sickle-Cell Anemia

Sickle-cell disease (SCD) affects millions worldwide. Sickle-cell anemia (SCA), the most severe form of this disease, is the most common inherited blood disorder in the United States. There are limited data on the incidence, clinical characteristics, and outcomes of acute myocardial infarction (AMI) in these patients. Using data from the National Inpatient Sample database, we matched cases (AMI with SCA) with controls (AMI without SCA) in a 1:1 ratio for age, gender, race, and year of admission. We compared both groups in terms of clinical characteristics and inpatient outcomes and performed a logistic regression with mortality as the primary outcome. Using weighted samples, we also described trends of SCA in the general population of patients with AMI. Of the 2,386,657 admissions with AMI, SCA was reported in 501 (0.02%) patients, and 495 were successfully matched to controls. Patients with SCA were less likely to have risk factors for coronary artery disease than those without SCA. Patients with SCA were more likely to develop pneumonia, respiratory failure, and acute renal failure, and require mechanical ventilation, hemodialysis for acute renal failure and blood transfusion. In-hospital mortality was significantly higher in patients with SCA. In a multivariate analysis, SCA was an independent predictor of mortality (odds ratio 3.49; 95% confidence interval 1.99 to 6.12; p = < .001). In conclusion, myocardial infarction occurs in patients with SCA at a relatively early age. These patients do not typically have the traditional risk factors for the acute coronary syndrome. Mortality in these patients is significantly higher in age-, gender-, and race-matched controls.

Sickle Cell Disease and Stroke: Diagnosis and Management

Both adult and pediatric patients with sickle cell disease face a higher risk of stroke than the general population. Given the different underlying pathophysiology predisposing these patients to stroke, providers should be aware of differences in guidelines for stroke management. This paper reviews diagnostic considerations and recommendations during the evaluation and acute management of patients with sickle cell disease presenting with stroke, focusing on recent updates in the literature. Given the high recurrence rate of stroke in these patients, secondary prevention and curative measures will also be reviewed.

Deep venous thrombosis in children with sickle cell disease

BACKGROUND

Deep venous thrombosis (DVT) is rare in children compared to adults. Its incidence and risk factors in children are not well known. This study determined these aspects of DVT in children with sickle cell disease (SCD).

PROCEDURE

A retrospective, observational and descriptive study was performed. Patients born between October 2000 and October 2012 with SCD and registered in HEMORIO, including those who died in HEMORIO, were included in this study. Patients whose medical records were inaccessible, who died in institutions other than HEMORIO, who died with implanted deep venous catheters, and those who were not monitored in HEMORIO for a period of 1 year or more were excluded from the study. Of a total of 1,519 patients, 456 were excluded and 1,063 patients were included in the study. Data were obtained from the computer system and the medical records at HEMORIO.

RESULTS

Of the 1,063 patients, 2 (0.2%) developed DVT with both cases being related to central venous catheters (CVCs) (P-value <0.001). Of the patients who required CVCs, the prevalence of DVT was 10%. No other variable was clinically or statistically significant with respect to DVT.

CONCLUSION

The establishment of CVCs in children with SCD poses a high risk for DVT. If this procedure is necessary, the internal jugular vein should be utilized instead of the subclavian and femoral veins. The identification of associated risk factors may justify antithrombotic prophylaxis.

Modulation of Sickle Red Blood Cell Adhesion and its Associated Changes in Biomarkers by Sulfated Nonanticoagulant Heparin Derivative

Abnormal cellular adhesion is one of the primary causes of vaso-occlusive crisis in sickle cell disease (SCD). Levels of intercellular adhesion molecule 1 (ICAM-1) and P-selectin are upregulated, resulting in increased adhesion of leukocytes and sickle red blood cells (RBCs) to endothelium. This study compares the inhibitory effect of a sulfated nonanticoagulant heparin (S-NACH) derivative with a low-molecular-weight heparin, tinzaparin, on the adhesion of sickle RBCs to endothelium. The S-NACH exhibits minimum effects on hemostasis and bleeding and interferes with the binding of pancreatic cancer cells to endothelial cells via P-selectin. We show by static binding assay that pretreatment of both erythrocytes and endothelial cells with S-NACH significantly inhibits the increased adhesion of sickle RBCs to endothelial cells. The S-NACH treatment also decreases the higher plasma levels of (adhesion biomarkers) ICAM-1 and P-selectin in SCD mice. This investigation signals further research into the potential use of S-NACH in treating vaso-occlusions with minimal bleeding events in patients with SCD.

The effect of prasugrel on ADP-stimulated markers of platelet activation in patients with sickle cell disease

Platelets of patients with sickle cell disease (SCD) show evidence of mild activation in the non-crisis steady state and greater activation during vaso-occlusive crises (VOC). Prasugrel, a potent inhibitor of ADP-mediated platelet activation and aggregation, may be useful in attenuating VOC. We compared platelet responses to ADP stimulation in patients with SCD and healthy subjects before and after treatment with prasugrel. In a phase 1 study, platelet biomarker levels were assessed in 12 adult patients with SCD and 13 healthy subjects before and after 12 ± 2 days of 5.0 or 7.5 mg/day prasugrel. The following were determined in whole blood samples stimulated with 20 µM ADP: (i) percentages of monocytes and neutrophils with adherent platelets (cell-platelet aggregates); (ii) the relative number (mass) of platelets associated with each monocyte and neutrophil as reported by CD61 mean fluorescence intensity (MFI) of the monocyte-platelet and neutrophil-platelet aggregates; (iii) the percentages of platelets positive for surface expression of CD40 ligand (CD40L), P-selectin (CD62p) and activated glycoprotein IIb-IIIa (GPIIb-IIIa); and (iv) the percentages of platelets and monocyte-platelet aggregates positive for surface tissue factor (TF) expression. At baseline, there were no significant differences between cohorts in the percentages of platelets expressing activation biomarkers. Following 12 days of prasugrel administration, the percentages of platelets expressing activation biomarkers following ADP stimulation were reduced in both cohorts, and there were no significant differences between groups. Both patients with SCD and healthy subjects had significant reductions in the monocyte-platelet and neutrophil-platelet aggregate MFI and the percentage of platelets expressing P-selectin and activated GPIIb-IIIa (all p < 0.05). Healthy subjects also had significant reductions in monocyte-platelet aggregate percentages (p = 0.004), neutrophil-platelet aggregate percentages (p = 0.011) and the percentage of CD40L-positive platelets (p = 0.044) that were not observed in patients with SCD. Prasugrel administration to SCD patients attenuates ex vivo ADP-stimulated platelet activation as measured by the percentage of platelets positive for P-selectin and GPIIb-IIIa, thus reducing the proportion of platelets that may participate in aggregates. Furthermore, prasugrel decreases ex vivo ADP-stimulated platelet aggregation with monocytes and neutrophils as measured by the monocyte-platelet and neutrophil-platelet aggregate MFI. This implies that in the presence of prasugrel, fewer platelets adhere to monocytes and neutrophils, which may result in reducing cell-platelet aggregate size. Therefore, reduced platelet reactivity and decreased size of leukocyte-platelet aggregates suggest additional mechanisms by which prasugrel may provide benefit to patients with SCD and support further investigation of possible therapeutic benefits of prasugrel in this population.

Outcome of overt stroke in sickle cell anaemia, a single institution's experience

Stroke is a traumatic complication in sickle cell anaemia (SCA) that is associated with significant morbidity and a risk of recurrent overt stroke of 2·2-6·4 events per 100 patient-years. A retrospective study was performed on all paediatric SCA patients diagnosed with a history of overt stroke between 1997 and 2010. A total of 31 children with SCA had new onset overt stroke. The mean age of the active patients (n = 27) was 17·9 years (range 6·8-27·6 years) with a total period of observation of 305 patient-years. Twenty-two of 27 (81%) were receiving long term red blood cell transfusions and 16 (59%) were taking the anti-platelet agent, aspirin, since diagnosis of the stroke. Two of 27 (7%) patients had a second overt stroke with an overall risk of recurrent stroke of 0·66/100 patient-years (one stroke was ischaemic and the other haemorrhagic). In patients taking aspirin with 180 patient-years of follow up, the recurrence rate of haemorrhagic stroke was 0·58/100 patient-years. We have an excellent outcome for overt stroke in paediatric SCA patients with a low rate of recurrent stroke. Further studies are needed to determine the risk-benefit ratio of aspirin therapy in the prevention of recurrent stroke in paediatric SCA.

Endothelial activation by platelets from sickle cell anemia patients

Sickle cell anemia (SCA) is associated with a hypercoagulable state. Increased platelet activation is reported in SCA and SCA platelets may present augmented adhesion to the vascular endothelium, potentially contributing to the vaso-occlusive process. We sought to observe the effects of platelets (PLTs) from healthy control (CON) individuals and SCA individuals on endothelial activation, in vitro. Human umbilical vein endothelial cells (HUVEC) were cultured, in the presence, or not, of washed PLTs from CON or steady-state SCA individuals. Supernatants were reserved for cytokine quantification, and endothelial adhesion molecules (EAM) were analyzed by flow cytometry; gene expressions of ICAM1 and genes of the NF-κB pathway were analyzed by qPCR. SCA PLTs were found to be more inflammatory, displaying increased adhesive properties, an increased production of IL-1β and a tendency towards elevated expressions of P-selectin and activated αIIbβ3. Following culture in the presence of SCA PLTs, HUVEC presented significant augmentations in the expressions of the EAM, ICAM-1 and E-selectin, as well as increased IL-8 production and increased ICAM1 and NFKB1 (encodes p50 subunit of NF-κB) gene expressions. Interestingly, transwell inserts abolished the effects of SCA PLTs on EAM expression. Furthermore, an inhibitor of the NF-κB pathway, BAY 11-7082, also prevented the induction of EAM expression on the HUVEC surface by SCA PLTs. In conclusion, we find further evidence to indicate that platelets circulate in an activated state in sickle cell disease and are capable of stimulating endothelial cell activation. This effect appears to be mediated by direct contact, or even adhesion, between the platelets and endothelial cells and via NFκB-dependent signaling. As such, activated platelets in SCD may contribute to endothelial activation and, therefore, to the vaso-occlusive process. Results provide further evidence to support the use of anti-platelet approaches in association with other therapies for SCD.

A phase 1 study of prasugrel in patients with sickle cell disease: pharmacokinetics and effects on ex vivo platelet reactivity

AIMS

Prasugrel is a novel thienopyridine P2Y12 adenosine diphosphate (ADP) receptor antagonist that inhibits ADP-mediated platelet activation and aggregation. Accordingly, it may be useful in reducing platelet-related ischaemia in sickle cell disease (SCD). Exposure to prasugrel's active metabolite (Pras-AM) and its antiplatelet activity in SCD have not been investigated.

METHODS

Thirteen adult patients with SCD and an equal number of matched healthy control subjects were studied before and after 12 days of 5.0 or 7.5 mg day(-1) prasugrel treatment. Platelet reactivity was assessed by light transmission aggregometry (LTA), impedance aggregometry (MEA), VerifyNow® P2Y12, vasodilator-stimulated phosphoprotein (VASP) phosphorylation and Plateletworks. Exposure to Pras-AM was also assessed.

RESULTS

At baseline, patients with SCD showed increased platelet reactivity vs. healthy control subjects with VerifyNow (408 vs. 323 P2Y12 reaction units (PRU), respectively, P = 0.003) and MEA (106 vs. 77 area under the aggregation curve (AU.min), P = 0.002); lower platelet reactivity index with VASP flow cytometry (59 vs. 79% platelet reactivity index (PRI), P = 0.018); and no significant differences with LTA, VASP enzyme-linked immunosorbent assay or Plateletworks. Relative to baseline, prasugrel significantly reduced platelet reactivity by all assays in both populations (all P < 0.05). Prasugrel was well tolerated, with no bleeding-related events in patients with SCD. The mean concentration-time profiles of Pras-AM were comparable between healthy subjects and patients with SCD following a single 10 mg prasugrel dose and following the 12th dose of 7.5 or 5 mg prasugrel.

CONCLUSIONS

Results demonstrate that in response to prasugrel, patients with SCD and healthy subjects have similar degrees of platelet inhibition and exposure to Pras-AM, and provide a basis for further study of prasugrel in patients with SCD.

A phase 1 study of prasugrel in patients with sickle cell disease: effects on biomarkers of platelet activation and coagulation

INTRODUCTION

Prasugrel, a P2Y₁₂ adenosine diphosphate (ADP) receptor antagonist effectively inhibits ADP-mediated platelet activation and aggregation, and may be useful in reducing vaso-occlusive crises in sickle cell disease (SCD). In this study, we assess the effect of prasugrel on biomarkers of platelet activation and coagulation in patients with SCD.

MATERIALS AND METHODS

Twelve adult patients with SCD and 13 healthy subjects were examined before and after 12 ± 2 days of 5.0 or 7.5 mg/day oral prasugrel. Assessed cellular biomarkers included monocyte- and neutrophil-platelet aggregates, activated glycoprotein IIb-IIIa (GPIIbIIIa), P-selectin, CD40 ligand (CD40L), tissue factor (TF) expression on circulating platelets and on monocyte-platelet aggregates, and platelet-erythrocyte aggregates. Soluble biomarkers included CD40L, prothrombin fragment 1.2 (F1.2), thromboxane B₂ (TXB₂), P-selectin, and TF.

RESULTS

Patients with SCD had increased platelet baseline activation compared to healthy subjects, as measured by percentages of monocyte-platelet aggregates, neutrophil-platelet aggregates, and platelets expressing CD40L. Likewise, baseline levels of soluble F1.2 and TXB₂ were elevated in patients with SCD compared to healthy subjects. After 12 days of prasugrel, patients with SCD had a significant reduction in platelet-monocyte aggregates that was not observed in healthy subjects. Following prasugrel administration, those with SCD maintained higher levels of monocyte-platelet aggregates and soluble F1.2, but had lower levels of platelet-erythrocyte aggregates and soluble TF compared to healthy subjects.

CONCLUSIONS

These results provide evidence for chronic platelet activation in the SCD steady state, activation that was in part attenuated by prasugrel, thereby suggesting that ADP may mediate platelet activation in SCD.

Stroke with intracranial stenosis is associated with increased platelet activation in sickle cell anemia

BACKGROUND

Overt stroke in sickle cell anemia (SCA) is associated with intracranial stenosis and thrombus formation. Platelet activation is critical for thrombus formation.

PROCEDURE

Platelet activation studies were performed in 50 subjects: 18 SCA patients with history of stroke or abnormal transcranial Doppler (TCD) and intracranial stenosis seen by magnetic resonance angiogram (MRA), 7 SCA patients with history of stroke or abnormal TCD but no intracranial stenosis, 13 SCA patients with no history of stroke or abnormal TCD, and 12 healthy African-Americans.

RESULTS

Of the 18 patients with intracranial stenosis, 11 (61%) had evidence of the moyo-moya phenomenon on MRA. SCA children with intracranial stenosis had a significantly greater total white cell count compared to both healthy African-American controls and SCA patients in the steady-state (P < 0.001). In addition, SCA patients with history of stroke or abnormal TCD had a significantly higher platelet count compared to healthy African-American controls (P < 0.002). The percentage of platelet surface P-selectin expression was significantly greater in patients with intracranial stenosis compared to the other groups (P < 0.05), particularly in individuals that did not have the moya-moya phenomenon seen on MRA.

CONCLUSION

Stroke with intracranial stenosis is associated with increased platelet activation in sickle cell anemia, and further investigation is needed on the role of anti-platelet agents in this high-risk population.

Identification of the Ca²⁺ entry pathway involved in deoxygenation-induced phosphatidylserine exposure in red blood cells from patients with sickle cell disease

Phosphatidylserine (PS) exposure in red blood cells (RBCs) from sickle cell disease (SCD) patients is increased compared to levels in normal individuals and may participate in the anaemic and ischaemic complications of SCD. Exposure is increased by deoxygenation and occurs with elevation of intracellular Ca²⁺ to low micromolar levels. The Ca²⁺ entry step has not been defined but a role for the deoxygenation-induced pathway, P_sickle, is postulated. Partial P_sickle inhibitors 4-acetamido-4′-isothiocyanostilbene-2,2′-disulphonic acid (SITS), 4,4′-dithiocyano-2,2′-stilbene-disulphonic acid (DIDS) and dipyridamole inhibited deoxygenation-induced PS exposure (DIDS IC₅₀, 118 nM). Inhibitors and activators of other pathways (including these stimulated by depolarisation, benzodiazepines, glutamate and stretch) were without effect. Zn²⁺ and Gd³⁺ stimulated PS exposure to high levels. In the case of Zn²⁺, this effect was independent of oxygen (and hence HbS polymerisation and RBC sickling) but required extracellular Ca²⁺. The effect was completely abolished when Zn²⁺ (100 μM) was added to RBCs suspended in autologous plasma, implying a requirement of high levels of free Zn²⁺.

Oocyte cryopreservation in a patient with sickle cell disease prior to hematopoietic stem cell transplantation: first report

PURPOSE

To report the first occurrence of successful ovarian stimulation, oocyte retrieval and oocyte cryopreservation for fertility preservation in an adolescent with severe sickle cell disease scheduled to undergo a hematopoietic stem cell transplant

METHODS

Case report.

RESULTS

A 19 year old female with severe sickle cell disease presented for fertility preservation counseling prior to hematopoietic stem cell transplantation. She ultimately underwent ovarian stimulation using a minimal stimulation GnRH antagonist protocol resulting in the successful banking of oocytes prior to transplant. The unique hazards associated with ovarian stimulation in patients with sickle cell disease, such as thrombosis and vaso-occlusive events, are discussed and the methods undertaken to minimize these risks are described.

CONCLUSIONS

Controlled ovarian hyperstimulation and oocyte banking for fertility preservation is feasible in young women with sickle cell disease requiring hematopoietic stem cell transplant and deserves further investigation. Given the elevated risk of thrombosis and predisposition to painful vaso-occlusive events, controlled ovarian hyperstimulation in patients with sickle cell disease is not straightforward and requires a multi-disciplinary team approach to adequately address and minimize the risks in this unique patient population.

The epidemiology, evaluation and treatment of stroke in adults with sickle cell disease

Stroke is a frequent and severe complication in adults with sickle cell disease. Ischemic stroke often causes physical and cognitive disability, while hemorrhagic stroke has a high mortality rate. As more children survive, the number of strokes in adults is increasing, yet stroke remains poorly understood. We review the epidemiology of ischemic and hemorrhagic stroke in adults with sickle cell disease and outline a practical approach to the evaluation of stroke including both sickle cell disease specific and general risk factors. We discuss the acute treatment and secondary prevention of stroke in this population based on the evidence in children with sickle cell disease and the general population, in addition to the limited studies in adults with sickle cell disease.

The role of infection in the pathogenesis of vaso-occlusive crisis in patients with sickle cell disease

Sickle cell disease (SCD) is characterized by recurrent vaso-occlusive crisis (VOC). Patients with SCD have impaired immunity and are thus predispose to infections. The vast majority of SCD patients live in underdeveloped nations with high prevalence and transmission rates of infections. This makes the SCD patients prone to infections, which frequently precipitate VOC. We reviewed the role of infection in the pathogenesis of VOC, taking into consideration all potential mechanisms from previous studies and hypothetical perspectives. The potential mechanisms through which infections may lead to VOC involve several pathological changes including pneumonitis, pyrexia, acute phase reaction, hypercoagulability, neutrophilia, eosinophilia, thrombocytosis, bronchospasm, red cell cytopathic and membrane changes, auto-antibodies mediated red cell agglutination and opsonization, diarrhoea and vomiting, which may act singly or in concert to cause red cell sickling. These changes can induce sickling directly or indirectly through their adverse effects on Hb oxygenation and polymerization, hydration, blood viscosity, red cell metabolism, procoagulant activation, intercellular adherence and aggregation, culminating in VOC. There is therefore the need to ameliorate the burden of infection on SCD through immunization, prophylactic and therapeutic use of antimicrobials, barrier protection and vector control in communities with high prevalence of SCD.