Erythropoiesis in sickle cell anaemia during acute infection and crisis.

Erythropoiesis was evaluated in 37 patients with sickle cell anaemia, 26 of them children under 12 years of age. Mean haemoglobin, haematocrit, reticulocyte, and erythropoietin levels were similar for 11 who were asymptomatic, 11 with infections, and 12 in vaso-occlusive crisis. Mean haemoglobin, haematocrit, and reticulocyte values were significantly lower and the mean erythropoietin level significantly higher for three patients in aplastic crisis. Reticulocyte counts reflected erythropoietic activity during the asymptomatic state but were variable during infection and crisis. No erythropoietic inhibitory activity was found in any of the four clinical states. It has been suggested that erythropoietin production decreases during infection. Patients in this study responded appropriately to stress, showing no decrease in erythropoietic activity during acute infection or crisis.     

Thrombotic microangiopathy in sickle cell disease crisis

Thrombotic microangiopathy (TMA) in patients with sickle cell disease (SCD) is a rare complication. These patients manifest microangiopathic hemolytic anemia (MAHA) with laboratory evidence of hemolytic anemia, schistocytosis, and thrombocytopenia. This is the first report of the syndrome in a group of these patients. A retrospective chart analysis of 10 consecutively diagnosed patients in SCD crisis who were referred for therapeutic plasma exchange (TPE) after developing MAHA was done. Patients had chest pain, respiratory distress, fever, pulmonary infiltrates, jaundice, and neurological dysfunction with abnormal liver function and coagulation tests. MAHA was diagnosed after a median hospital stay of 5 days. Nine patients recovered completely following TPE with fluid replacement by fresh frozen plasma with or without cryo-poor plasma. Incomplete response to TPE in one case was due to the development of fresh complications. During a median follow-up period of 77 months, there was one recurrent episode and one death in SCD crisis but without evidence of MAHA. TMA is not a very rare complication among Bahraini SCD patients in crisis. Characteristic features of this disorder are acute chest syndrome, organ failure, leuco-erythroblastosis, and a combination of thrombocytopenia, LDH level >1,000 U/l, and schistocytes in blood smears. Management with TPE usually leads to complete recovery with little chance of short-term recurrence. Multiple pathogenetic mechanisms leading to increased von Willebrand factor and its multimers may form the basis of this syndrome.     

Impaired renal tubular potassium secretion in sickle cell disease.

We examined renal tubular function in six patients with sickle cell hemoglobin. All had normal inulin and para-aminohippurate clearances and impaired urinary concentrating and acidifying abilities. After intravenous potassium chloride administration, maximum excretion of potassium (U,V) was significantly lower in sickle cell patients than in control subjects, and the percentage of potassium load excreted in 5 h was markedly reduced. Urinary potassium excretion after sodium sulfate infusion was also markedly reduced in sickle cell patients compared to control subjects. After 40 mg of oral furosemide, U,V was also diminished in sickle cell patients. Plasma aldosterone response to ACTH and intravenous potassium was similar to that of control subjects. Plasma renin activity increased normally after volume contraction. We conclude that sickle cell patients have a defect in their ability to excrete an acute potassium load that cannot be attributed to abnormal renin or aldosterone secretion. Overall potassium homeostasis is maintained by extrarenal mechanisms during acute potassium loading.     

Abnormalities of coagulation and fibrinolysis in homozygous sickle cell disease

Abnormalities of coagulation and fibrinolysis were studied in a group of 28 children and young adults with homozygous sickle cell disease (SCD), either in the steady state (n = 12) or during painful crisis (n = 16). Coagulation was explored by standard clotting tests and by measurement of prothrombin complex factors, factor VIII (VIII:C) and antithrombin III (ATIII), protein C (PC) and protein S (PS) activities, while fibrinolytic potential was evaluated using D-dimer, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI-1) assays. In SCD patients, thrombin time (TT) was constantly shortened, both in the steady state (ratio to control 0.83 ± 0.08, p < 0.0001) and in crisis (0.76 ± 0.06, p < 0.0001). Mean levels of prothrombin complex were similar in asymptomatic patients to those in controls, but were significantly decreased during sickle cell crisis (p < 0.05 for factor V and p < 0.0001 for factors II,VII and X). Factor VIII:C was significantly increased, both in the steady state (207 ± 35%, p < 0.0001) and during crisis (208 ± 34 %, p < 0,0001). PS activity was reduced in the steady state (81 ± 12%, p < 0.01) and further diminished in crisis (68.5 ± 27.5%, p < 0.001), while D-dimers were significantly elevated during sickle cell crisis (1028 ± 675 ng/ml, p < 0.001). In all SCD patients, baseline levels of t-PA antigen were comparable to those in controls, whereas concentrations of PAI-1 antigen were significantly increased, either in the steady state (89.7 ± 26.3 ng/ml, p < 0.0001) or in crisis (75.0 ± 24.8 ng/ml, p < 0.0001). These results provide evidence for the presence of circulating activated clotting factors in SCD and for an imbalance of the profibrinolytic and antifibrinolytic systems most likely due to increased PAI-1 levels.     

Abnormalities of coagulation and fibrinolysis in homozygous sickle cell disease

Abnormalities of coagulation and fibrinolysis were studied in a group of 28 children and young adults with homozygous sickle cell disease (SCD), either in the steady state (n = 12) or during painful crisis (n = 16). Coagulation was explored by standard clotting tests and by measurement of prothrombin complex factors, factor VIII (VIII:C) and antithrombin III (ATIII), protein C (PC) and protein S (PS) activities, while fibrinolytic potential was evaluated using D-dimer, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI-1) assays. In SCD patients, thrombin time (TT) was constantly shortened, both in the steady state (ratio to control 0.83 ± 0.08, p < 0.0001) and in crisis (0.76 ± 0.06, p < 0.0001). Mean levels of prothrombin complex were similar in asymptomatic patients to those in controls, but were significantly decreased during sickle cell crisis (p < 0.05 for factor V and p < 0.0001 for factors II,VII and X). Factor VIII:C was significantly increased, both in the steady state (207 ± 35%, p < 0.0001) and during crisis (208 ± 34 %, p < 0,0001). PS activity was reduced in the steady state (81 ± 12%, p < 0.01) and further diminished in crisis (68.5 ± 27.5%, p < 0.001), while D-dimers were significantly elevated during sickle cell crisis (1028 ± 675 ng/ml, p < 0.001). In all SCD patients, baseline levels of t-PA antigen were comparable to those in controls, whereas concentrations of PAI-1 antigen were significantly increased, either in the steady state (89.7 ± 26.3 ng/ml, p < 0.0001) or in crisis (75.0 ± 24.8 ng/ml, p < 0.0001). These results provide evidence for the presence of circulating activated clotting factors in SCD and for an imbalance of the profibrinolytic and antifibrinolytic systems most likely due to increased PAI-1 levels.     

The management of crisis in sickle cell disease

Abstract: The symptoms and signs of sickle cell disease are exacerbated in times of crisis, characterized by tissue infarction or worsening anaemia. Prompt medical intervention is required in these distressing situations to provide relief and comfort to the patient. Effective analgesia is crucial in treating the painful crisis of sickle cell disease. The haemoglobinopathy may cause hyposthenuria with reduced ability to excrete the sodium load in normal saline. A 5% dextrose solution or 5% dextrose in 25% normal saline is therefore recommended for intravenous hydration. As the leading cause of morbidity and mortality in sickle cell disease, infections call for vigorous antibiotic therapy. Oxygen administration should be reserved for hypoxic patients, and blood transfusion given only when really indicated. Acute chest syndrome and cerebrovascular accidents are life-threatening complications of sickle cell disease whereas priapism can cause important long-term sequelae; all deserve urgent attention. In the long term, comprehensive care is cost-effective in reducing the frequency and adverse effects of sickle cell crisis.     

Nucleosomes and neutrophil activation in sickle cell disease painful crisis

Activated polymorphonuclear neutrophils play an important role in the pathogenesis of vaso-occlusive painful sickle cell crisis. Upon activation, polymorphonuclear neutrophils can form neutrophil extracellular traps. Neutrophil extracellular traps consist of a meshwork of extracellular DNA, nucleosomes, histones and neutrophil proteases. Neutrophil extracellular traps have been demonstrated to be toxic to endothelial and parenchymal cells. This prospective cohort study was conducted to determine neutrophil extracellular trap formation in sickle cell patients during steady state and painful crisis. As a measure of neutrophil extracellular traps, plasma nucleosomes levels were determined and polymorphonuclear neutrophil activation was assessed measuring plasma levels of elastase-α1-antitrypsin complexes in 74 patients in steady state, 70 patients during painful crisis, and 24 race-matched controls using Enzyme Linked Immunosorbent Assay. Nucleosome levels in steady state sickle cell patients were significantly higher than levels in controls. During painful crisis levels of both nucleosomes and elastase-α1-antitrypsin complexes increased significantly. Levels of nucleosomes correlated significantly to elastase-α1-antitrypsin complex levels during painful crisis, (Sr = 0.654, P<0.001). This was seen in both HbSS/HbSβ⁰-thalassemia (Sr=0.55, P<0.001) and HbSC/HbSβ^+-thalassemia patients (Sr=0.90, P<0.001) during painful crisis. Levels of nucleosomes showed a correlation with length of hospital stay and were highest in patients with acute chest syndrome. These data support the concept that neutrophil extracellular trap formation and neutrophil activation may play a role in the pathogenesis of painful sickle cell crisis and acute chest syndrome.     

Impaired fibrinolysis in coronary artery disease

We assessed endogenous endothelial-dependent fibrinolysis in 99 subjects with coronary artery disease (CAD) documented by angiography and in 28 control subjects with normal coronary arteries on angiography. We used specific, sensitive assays for plasma tissue-type plasminogen activator (t-PA) antigen, t-PA activity, plasminogen activator inhibitor (PAI) activity, plasminogen, and alpha-2 plasmin inhibitor (alpha-2 PI). Mean PAI activity was significantly higher, and mean t-PA activity after venous occlusion of the upper arm (a standard test of the capacity of vascular endothelium to release t-PA) was significantly lower in subjects with CAD than in subjects with normal coronary arteries. The mean increment in t-PA antigen after venous occlusion was significantly lower than normal in subjects with CAD with onset of symptoms before age 45 years. Subjects with CAD had a significantly increased mean plasma fibrinogen level compared with control subjects, and a significant positive correlation was observed between PAI activity and plasma fibrinogen in subjects with CAD. No significant abnormalities of plasminogen or alpha-2 PI were observed in any subset of subjects with CAD. These data support an association between impaired fibrinolysis and CAD, with contributions from both increased PAI activity and in younger subjects from reduced endothelial t-PA release.     

Impaired vasodilation by red blood cells in sickle cell disease

Red blood cells (RBCs) have been ascribed a unique role in dilating blood vessels, which requires O2-regulated binding and bioactivation of NO by Hb and transfer of NO equivalents to the RBC membrane. Vasoocclusion in hypoxic tissues is the hallmark of sickle cell anemia. Here we show that sickle cell Hb variant S (HbS) is deficient both in the intramolecular transfer of NO from heme iron (iron nitrosyl, FeNO) to cysteine thiol (S-nitrosothiol, SNO) that subserves bioactivation, and in transfer of the NO moiety from S-nitrosohemoglobin (SNO-HbS) to the RBC membrane. As a result, sickle RBCs are deficient in membrane SNO and impaired in their ability to mediate hypoxic vasodilation. Further, the magnitudes of these impairments correlate with the clinical severity of disease. Thus, our results suggest that abnormal RBC vasoactivity contributes to the vasoocclusive pathophysiology of sickle cell anemia, and that the phenotypic variation in expression of the sickle genotype may be explained, in part, by variable deficiency in RBC processing of NO. More generally, our findings raise the idea that defective NO processing may characterize a new class of hemoglobinopathy.     

Ambulatory quality indicators to prevent infection in sickle cell disease

The purpose of this study was to identify rates of adherence for three outpatient quality indicators noted by Wang et al. (Pediatrics 2011;128:484–493): (1) influenza vaccine, (2) pneumococcal immunizations, and (3) penicillin prophylaxis in patients with sickle cell disease (SCD) in a Medicaid sample. These variables were chosen based on Wang and colleagues' suggestion that these variables are important for the assessment of the quality of care of children with SCD. We hypothesized that the overall rate of adherence would be poor with adults having worse rates of adherence than children. We conducted a retrospective cohort study using the Wisconsin State Medicaid database over a 5‐year period to assess the preventative medication adherence of individuals with SCD. Preventative medication variables in this study included influenza vaccination, pneumococcal immunizations (PCV7, PPV23), and penicillin prophylaxis. As predicted, the 2003–2007 Wisconsin State Medicaid database showed patients with SCD had low adherence in terms of recommended influenza vaccinations (21.58% adherent), PPV23 pneumococcal immunizations (43.47% adherent), and penicillin prophylaxis (18.18% adherent). Pneumococcal immunizations for PCV7 were higher than expected (77.27% adherent). Although children tended to adhere to recommended preventative medications more than adults, overall adherence was low. Although we cannot explain why adherence is low, it is likely due to multiple factors at the patient‐ and provider‐level. We encourage patients and providers to create a partnership to meet adherence recommendations, and we describe our strategies for increasing adherence. Am. J. Hematol. 89:256–260, 2014. © 2013 Wiley Periodicals, Inc.     

Normal sublingual microcirculation during painful crisis in sickle cell disease

Obstruction of the microcirculation is the most important cause of painful crisis in sickle cell disease (SCD). Extensive microvascular obstruction has been observed in mouse models of SCD. A technique to determine the extent of the microcirculatory obstructions in humans may be helpful in the clinical setting and for research purposes. Therefore, we measured sublingual microcirculation longitudinally in patients with SCD admitted with painful crisis.Sublingual microcirculation was recorded with side-stream darkfield (SDF) imaging and semi-quantified with a microvascular flow index (MFI) on a range from 0 to 4 (arbitrary units; from 0 (no flow) to 4 (hyperdynamic flow)).Thirteen consecutive adult sickle cell patients admitted with painful crises were included and provided 47 measurements of MFI in 14 episodes of painful crisis. Seven patients provided baseline measurements and seven healthy controls were studied. The mean (± standard error of the mean) MFI during painful crisis was 2.6 ± 0.1 and did not change during the painful crisis. The mean MFI of patients with SCD during steady state (2.7 ± 0.1) and the mean MFI of the controls (2.7 ± 0.1) were not different from the mean MFI during painful crisis. During painful crisis irregular microvascular perfusion, expressed by the distribution width of the microvascular blood flow velocity, correlated negatively (r = − 0.484; P = 0.002) with hemoglobin concentration.We conclude that sublingual microcirculatory blood flow velocity is not disturbed in sickle cell patients during painful crisis.     

Breathing patterns during vaso-occlusive crisis of sickle cell disease

STUDY OBJECTIVES: To determine the effect of sickle cell pain and its treatment on patients' breathing patterns, and to compare the effect of thoracic cage pain to pain at other sites. DESIGN: Prospective, observational study. SETTING: Sickle Cell Center Day Hospital. PATIENTS: Twenty-five patients with sickle cell disease admitted to the Sickle Cell Center Day Hospital for treatment of vaso-occlusive crisis (VOC) [10 patients with chest (thoracic cage) pain]. INTERVENTIONS: Breathing patterns were measured by respiratory inductive plethysmography. Tidal breathing data, including respiratory rate, tidal volume (VT), minute ventilation, and the rib cage contribution to VT, were collected at baseline and then following treatment with opioid analgesia. MEASUREMENTS AND RESULTS: The patients with chest pain had smaller V(Ts) at baseline than those with pain at other sites (355 +/- 37 mL vs 508 +/- 141 mL, p = 0.003), and higher respiratory rates (23.2 +/- 8.2 breaths/min vs 17.6 breaths/min, p = 0.03). These differences became insignificant following opioid treatment. Six patients had respiratory alternans (four patients in the chest pain group, and two patients with pain at other sites). All cases of respiratory alternans resolved following opioid administration. CONCLUSIONS: Patients with VOC and chest pain have more shallow, rapid breathing than patients with pain elsewhere. Analgesia reduces these differences. As pain-associated shallow breathing and maldistribution of ventilation may contribute to the pathogenesis of acute chest syndrome, these results support the need for adequate pain relief and monitoring of ventilatory patterns during the treatment of VOC.     

Reduced vitamin E antioxidant capacity in sickle cell disease is related to transfusion status but not to sickle crisis

In homozygous sickle cell disease (SCD), decreased serum Vitamin E is present. Excessive transfusions may lead to iron overload. We hypothesised a relationship between the two and found that Vitamin E type antioxidant capacity was significantly lower in 30 SCD patients than in 30 age- and sex-matched controls (P < 0.001). Antioxidant capacity was lower in 10 transfused patients compared with 20 non-transfused patients (P < 0.001). Transfusional iron overload in SCD may increase the potential for oxidative damage, and low antioxidant capacity may compound this effect.     

The relation of C-reactive protein to vasoocclusive crisis in children with sickle cell disease

Vasoocclusive crisis (VOC) is the major cause of morbidity and mortality in sickle cell anemia (SCA), which is caused by the occlusion of blood vessels, followed by ischemia or infarct, resulting in progressive damage to organs. However, this clinical manifestation is variable, indicating that this process could be influenced by modifier genes. The gene MBL2 which codes for mannose-binding lectin (MBL) has been associated with modifications in the progression of infectious and inflammatory vascular diseases. The aim of this study was to determine the frequency of the polymorphisms of exon 1 (alleles A/O) and promoter region ? 221 (alleles Y/X) of MBL2 in children with SCA and to verify their association with VOC. The determination of the polymorphism of exon 1 and the promoter region of MBL2 was performed by SYBR GREEN^® and Taqman^® system, respectively. In the patients with SCA, the frequency of the genotype related to high production of MBL was 0.46 (YA/YA) and for intermediate/low production was 0.54 (YA/XA, XA/XA, YA/YO, XA/YO, YO/YO). The frequency of the genotypes and haplotypes of MBL2 in patients with SCA did not differ from control individuals. The populations were in Hardy–Weinberg equilibrium. The patients were divided into two groups. The groups were separated by the frequency of VOC, which was defined by the total of VOC episodes divided by the age of the children at the end of this study. Since, we choose a cut point in FVOC < 1 (n = 48) (which we considered of mild presentation of disease) and FVOC ≥ 1 (n = 39) (higher severity). In children with SCA, the frequency of the genotypes of MBL2 of intermediate/low expression for MBL was associated with FVOC ≥ 1 (p = 0.0188 OR = 3.15 CI = 1.19–8.50). The results suggest that MBL2 polymorphism at promoter and first exon of MBL2 associated with low serum levels and structural alterations of MBL could modify the phenotype of the child with SCA related to VOC.     

How we prevent and manage infection in sickle cell disease

Sickle cell disease (SCD) affects approximately 100 000 people in the US, 12 500 in the UK, and millions worldwide. SCD is typified by painful vaso‐occlusive episodes, haemolytic anaemia and organ damage. A secondary complication is infection, which can be bacterial, fungal or viral. Universal newborn screening, routine use of penicillin prophylaxis, availability of conjugated vaccines against S. pneumoniae and comprehensive care programmes instituted during the past few decades in industrialized countries have dramatically reduced childhood mortality and improved life expectancy. Yet patients with SCD remain at increased risk of infection. Unfortunately, the treatment of most bacterial infections that are common in SCD is not based on the results of randomized controlled clinical trials. In their absence, treatment decisions are based on consensus guidelines, clinical experience or adapting treatment applied in other diseases. This leads to wide variation in treatment among institutions and even between treating physicians in a single institution. Prevention of infection, when possible, is most important and we focus on prevention through targeted prophylaxis and vaccination. We will share our management strategies for managing the more common infections in SCD and provide the rationale for our recommendations.     

Aplastic crisis in sickle cell disorders: bone marrow necrosis and human parvovirus infection

Aplastic crisis in patients with sickle cell disease who develop a parvovirus infection may be associated with extensive bone marrow necrosis as well as acute selective erythroblastopenia. This illness may be manifested by pyrexia, lymphadenopathy, bone tenderness and significant hypoxemia with minimal roentgenographic findings in the lungs. It is uncertain whether the hypoxemia is caused by the effects of the viral infection on the lungs or is secondary to sickling of red blood cells in the pulmonary vasculature or both. The hypoxia may be sufficiently severe to require treatment with both oxygen and transfusion. The physical damage to the bone marrow associated with bone marrow necrosis may be more important than selective acute erythroblastopenia in inducing aplastic crisis in patients with sickle cell disorders. Studies of bone marrow biopsy specimens collected during parvovirus-associated aplastic crisis in patients with nonsickle cell hemolytic disorders would be helpful in determining the pathophysiology of parvovirus-associated disorders.     

Left ventricular performance during and after sickle cell crisis.

Although microvascular occlusion has been considered a basis for pathophysiology of the myocardium during the crisis of sickle cell anemia, the status of the left ventricle in uncertain. To determine if left ventricular performance is affected by crisis, 11 patients were evaluated noninvasively by the systolic time interval method on the first day of crisis and serially until recovery. There were no significant differences in the time intervals over this period. In addition, since the serum CPK-MB isoenzyme was not elevated during crisis and evidence of acute injury was not present on ECG, myocardial necrosis appeared unlikely. Four patients on subsequent admission exhibited systolic time interval values similar to the earlier crisis. To determine if there were chronic changes in cardiac function, subjects with sickle cell hemoglobin were studied between crises. Those under 23 years of age were not dissimilar from a group of normals and a group of patients with chronic blood loss anemia A significant abnormality of the PEP/LVET ratio was observed in subjects over 23 years of age. Similar observations were made on echocardiography, with subjects over the age of 23 demonstrating an abnormal ejection fraction compared to the younger group, despite enhanced end-diastolic diameter. Thus, it is suggested that the chronic hemolytic process in subjects with sickle cell anemia may effect cumulative myocardial alterations, resulting in chronic cardiac malfunction in the apparent absence of acute ischemia during crises.     

The painful crisis of homozygous sickle cell disease: clinical features

The details of onset, perceived precipitating factors, associated symptoms, and pain distribution in the painful crisis of homozygous sickle cell (SS) disease have been prospectively recorded in 183 painful crises in 118 patients admitted to a day-care centre in Kingston, Jamaica. Painful crises developed most frequently between 3 p.m. and midnight, most commonly affected patients aged 15-29 years, affected the sexes equally, and were not obviously influenced by menstrual cycle. Of the perceived precipitating factors, skin cooling occurred in 34%, emotional stress in 10%, physical exertion in 7%, and pregnancy in 5% of women of child-bearing age. Cold as a precipitant was not less common in patients with more subcutaneous fat. Pain affected the lumbar spine in 49%, abdomen in 32%, femoral shaft in 30%, and knees in 21%. There was a highly significant excess of bilateral involvement in limb and rib pain. Recurrent painful crises occurred in 40 patients but showed no evidence of involving similar sites on successive occasions. Abdominal painful crises were associated with abdominal distention in 18 (31%) and with referred rib pain in a further 15 (26%) of crises. Fever was common even in apparently uncomplicated painful crises, suggesting that fever is characteristic of the painful crisis itself and not necessarily indicative of infection. Following investigation and treatment in a day-care centre, over 90% of patients returned home.