Management of cerebral vasculopathy in children with sickle cell anaemia

Blood transfusion for preventing primary and secondary stroke in people with sickle cell disease

BACKGROUND

Sickle cell disease is one of the commonest severe monogenic disorders in the world, due to the inheritance of two abnormal haemoglobin (beta globin) genes. Sickle cell disease can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Stroke affects around 10% of children with sickle cell anaemia (HbSS). Chronic blood transfusions may reduce the risk of vaso-occlusion and stroke by diluting the proportion of sickled cells in the circulation. This is an update of a Cochrane Review first published in 2002, and last updated in 2017.

OBJECTIVES

To assess risks and benefits of chronic blood transfusion regimens in people with sickle cell disease for primary and secondary stroke prevention (excluding silent cerebral infarcts).

SEARCH METHODS

We searched for relevant trials in the Cochrane Library, MEDLINE (from 1946), Embase (from 1974), the Transfusion Evidence Library (from 1980), and ongoing trial databases; all searches current to 8 October 2019. We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Haemoglobinopathies Trials Register: 19 September 2019.

SELECTION CRITERIA

Randomised controlled trials comparing red blood cell transfusions as prophylaxis for stroke in people with sickle cell disease to alternative or standard treatment. There were no restrictions by outcomes examined, language or publication status.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility and the risk of bias and extracted data.

MAIN RESULTS

We included five trials (660 participants) published between 1998 and 2016. Four of these trials were terminated early. The vast majority of participants had the haemoglobin (Hb)SS form of sickle cell disease. Three trials compared regular red cell transfusions to standard care in primary prevention of stroke: two in children with no previous long-term transfusions; and one in children and adolescents on long-term transfusion. Two trials compared the drug hydroxyurea (hydroxycarbamide) and phlebotomy to long-term transfusions and iron chelation therapy: one in primary prevention (children); and one in secondary prevention (children and adolescents). The quality of the evidence was very low to moderate across different outcomes according to GRADE methodology. This was due to the trials being at a high risk of bias due to lack of blinding, indirectness and imprecise outcome estimates. Red cell transfusions versus standard care Children with no previous long-term transfusions Long-term transfusions probably reduce the incidence of clinical stroke in children with a higher risk of stroke (abnormal transcranial doppler velocities or previous history of silent cerebral infarct), risk ratio 0.12 (95% confidence interval 0.03 to 0.49) (two trials, 326 participants), moderate quality evidence. Long-term transfusions may: reduce the incidence of other sickle cell disease-related complications (acute chest syndrome, risk ratio 0.24 (95% confidence interval 0.12 to 0.48)) (two trials, 326 participants); increase quality of life (difference estimate -0.54, 95% confidence interval -0.92 to -0.17) (one trial, 166 participants); but make little or no difference to IQ scores (least square mean: 1.7, standard error 95% confidence interval -1.1 to 4.4) (one trial, 166 participants), low quality evidence. We are very uncertain whether long-term transfusions: reduce the risk of transient ischaemic attacks, Peto odds ratio 0.13 (95% confidence interval 0.01 to 2.11) (two trials, 323 participants); have any effect on all-cause mortality, no deaths reported (two trials, 326 participants); or increase the risk of alloimmunisation, risk ratio 3.16 (95% confidence interval 0.18 to 57.17) (one trial, 121 participants), very low quality evidence. Children and adolescents with previous long-term transfusions (one trial, 79 participants) We are very uncertain whether continuing long-term transfusions reduces the incidence of: stroke, risk ratio 0.22 (95% confidence interval 0.01 to 4.35); or all-cause mortality, Peto odds ratio 8.00 (95% confidence interval 0.16 to 404.12), very low quality evidence. Several review outcomes were only reported in one trial arm (sickle cell disease-related complications, alloimmunisation, transient ischaemic attacks). The trial did not report neurological impairment, or quality of life. Hydroxyurea and phlebotomy versus red cell transfusions and chelation Neither trial reported on neurological impairment, alloimmunisation, or quality of life. Primary prevention, children (one trial, 121 participants) Switching to hydroxyurea and phlebotomy may have little or no effect on liver iron concentrations, mean difference -1.80 mg Fe/g dry-weight liver (95% confidence interval -5.16 to 1.56), low quality evidence. We are very uncertain whether switching to hydroxyurea and phlebotomy has any effect on: risk of stroke (no strokes); all-cause mortality (no deaths); transient ischaemic attacks, risk ratio 1.02 (95% confidence interval 0.21 to 4.84); or other sickle cell disease-related complications (acute chest syndrome, risk ratio 2.03 (95% confidence interval 0.39 to 10.69)), very low quality evidence. Secondary prevention, children and adolescents (one trial, 133 participants) Switching to hydroxyurea and phlebotomy may: increase the risk of sickle cell disease-related serious adverse events, risk ratio 3.10 (95% confidence interval 1.42 to 6.75); but have little or no effect on median liver iron concentrations (hydroxyurea, 17.3 mg Fe/g dry-weight liver (interquartile range 10.0 to 30.6)); transfusion 17.3 mg Fe/g dry-weight liver (interquartile range 8.8 to 30.7), low quality evidence. We are very uncertain whether switching to hydroxyurea and phlebotomy: increases the risk of stroke, risk ratio 14.78 (95% confidence interval 0.86 to 253.66); or has any effect on all-cause mortality, Peto odds ratio 0.98 (95% confidence interval 0.06 to 15.92); or transient ischaemic attacks, risk ratio 0.66 (95% confidence interval 0.25 to 1.74), very low quality evidence.

AUTHORS' CONCLUSIONS

There is no evidence for managing adults, or children who do not have HbSS sickle cell disease. In children who are at higher risk of stroke and have not had previous long-term transfusions, there is moderate quality evidence that long-term red cell transfusions reduce the risk of stroke, and low quality evidence they also reduce the risk of other sickle cell disease-related complications. In primary and secondary prevention of stroke there is low quality evidence that switching to hydroxyurea with phlebotomy has little or no effect on the liver iron concentration. In secondary prevention of stroke there is low-quality evidence that switching to hydroxyurea with phlebotomy increases the risk of sickle cell disease-related events. All other evidence in this review is of very low quality.

Leucocytosis and Asymptomatic Urinary Tract Infections in Sickle Cell Patients at a Tertiary Hospital in Zambia

Sickle cell anaemia (SCA) is an inherited disease resulting from mutations in the β-globin chain of adult haemoglobin that results in the formation of homozygous sickle haemoglobin. It is associated with several complications including an altered blood picture and damage in multiple organs, including the kidneys. Kidney disease is seen in most patients with SCA and may affect glomerular and/or tubular function, thereby putting these patients at risk of urinary tract infections. However, there is a paucity of data on the prevalence of urinary tract infections (UTIs) among SCA patients in Zambia. This study aimed to determine the prevalence of UTIs and haematological and kidney function profiles among SCA patients at the University Teaching Hospitals, Lusaka, Zambia. This was a cross-sectional study conducted between April and July 2019 involving 78 SCA patients who presented at the UTH. Blood and midstream urine samples were collected from each participant using the standard specimen collection procedures. Full blood counts and kidney function tests were determined using Sysmex XT-4000i haematology analyser and the Pentra C200 by Horiba, respectively. Bacterial profiles of the urine samples were determined using conventional microbiological methods. We found that all the measured patients' haemoglobin (Hb) levels fell below the WHO-recommended reference range with a minimum of 5 g/dl, a maximum of 10.5 g/dl, and a mean of 8 ± 1 g/dl. Fifty percent of the participants had moderate anaemia, while the other 50% had severe anaemia. The minimum WBC count of the participants was 0.02 × 10⁹/L with a maximum of 23.36 × 10⁹/L and a mean of 13.48 ± 3.87 × 10⁹/L. Using the one-way analysis of variance test, we found no significant difference in mean WBC count and Hb concentration across various age-group categories that we defined. Bacteriuria was found in 25% of participants. The most common bacterial isolates were Staphylococcus aureus (32%) and coagulase-negative Staphylococci (32%). Klebsiella pneumoniae was 16%. We found no significant association between bacterial isolates and white blood cell count, age groups, sex, and anaemia severity p = 0.41. None of the participants were diagnosed with kidney disease. There was a high prevalence of asymptomatic UTIs among SCA patients at UTH, which, when coupled with the marked leukocytosis and anaemia, may negatively impact the clinical outcome of the patients. Therefore, we recommend close monitoring of sickle cell patients in Zambia for such conditions to improve patients' outcomes.

Cerebral Revascularization for Moyamoya Syndrome Associated with Sickle Cell Disease: A Systematic Review of the Literature on the Role of Extracranial-Intracranial Bypass in Treating Neurologic Manifestations of Pediatric Patients with Sickle Cell Disease

Moyamoya syndrome (MMS) in patients with sickle cell disease (SCD) accentuates the risk of recurrent strokes. Chronic transfusion therapy (CTT) is an excellent option for preventing recurrent strokes in most patients with SCD. In SCD with MMS, CTT may fail as a long-term solution. Cerebral revascularization, in the form of extracranial-intracranial bypass, has been shown to prevent recurrent strokes in this cohort. We review the evolution of this paradigm shift in the management of SCD-associated MMS. A systematic review, adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol, was conducted. Our primary objectives were 1) to study the evolution of cerebral revascularization techniques in management of MMS in SCD and 2) to analyze the impact of neurosurgical intervention in this high-risk population. Four patients with SCD-associated MMS, who underwent indirect cerebral revascularization at our institute were retrospectively reviewed. A summary of 13 articles chronicling the advent and subsequent evolution of cerebral revascularization as a viable treatment strategy for stroke prevention in SCD-associated MMS is presented. The literature review suggests that early detection and surgical intervention (in addition to CTT) could significantly reduce stroke recurrence and improve neurocognitive outcome. Our short series of 4 patients also had a good outcome and no recurrence of strokes postoperatively. The literature emphasizes the use of a traditional standardized protocol for early identification (transcranial Dopplers, selective magnetic resonance angiography, and CTT). Early treatment and screening that involves early magnetic resonance angiography and referral to neurosurgery for revascularization may be considered for this high-risk population.

Hidden hearing loss in children and adolescents with sickle cell anemia

OBJECTIVE

To evaluate the auditory system for hidden hearing loss (HHL) and its association with clinical variables and endothelial dysfunction (ED) in children and adolescents with sickle cell anemia (SCA).

METHODS

Participants included 37 patients with stable SCA and 44 healthy controls (HC group) (aged 6-18 years) with hearing thresholds ≤ 20 dB (dB) were evaluated for pure tone audiometry, tympanometry, acoustic reflex, otoacoustic emission, and auditory evoked potentials. Laboratory analysis of the lipid profile, and C-reactive protein levels and endothelial function using ultrasonographic imaging of the brachial artery to assess flow-mediated dilation were performed.

RESULTS

The SCA group presented with a higher rate of increased contralateral acoustic reflex thresholds, compared to those in the HC group at all frequencies and in both ears (p < 0.05). There were significant differences in the brainstem auditory evoked potentials between the SCA and HC groups. In the SCA group, the waves III and V latencies were increased (p = 0.006 and 0.004 respectively), and the I-III and I-V interpeak intervals were longer (p = 0.015 and 0.018 respectively) than those in the HC group. There was no association between the audiological measures and clinical and metabolic variables and sickle cell anemia complications including endothelial function and therapy.

CONCLUSION

In conclusion, our findings suggest that damage in the auditory system in SCA patients can be present involving retrocochlear structures, causing functional deficits without deterioration of auditory sensitivity.

Blood transfusion for preventing primary and secondary stroke in people with sickle cell disease

BACKROUND

Sickle cell disease is one of the commonest severe monogenic disorders in the world, due to the inheritance of two abnormal haemoglobin (beta globin) genes. Sickle cell disease can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Stroke affects around 10% of children with sickle cell anaemia (HbSS). Chronic blood transfusions may reduce the risk of vaso-occlusion and stroke by diluting the proportion of sickled cells in the circulation.This is an update of a Cochrane Review first published in 2002, and last updated in 2013.

OBJECTIVES

To assess risks and benefits of chronic blood transfusion regimens in people with sickle cell disease for primary and secondary stroke prevention (excluding silent cerebral infarcts).

SEARCH METHODS

We searched for relevant trials in the Cochrane Library, MEDLINE (from 1946), Embase (from 1974), the Transfusion Evidence Library (from 1980), and ongoing trial databases; all searches current to 04 April 2016.We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Haemoglobinopathies Trials Register: 25 April 2016.

SELECTION CRITERIA

Randomised controlled trials comparing red blood cell transfusions as prophylaxis for stroke in people with sickle cell disease to alternative or standard treatment. There were no restrictions by outcomes examined, language or publication status.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility and the risk of bias and extracted data.

MAIN RESULTS

We included five trials (660 participants) published between 1998 and 2016. Four of these trials were terminated early. The vast majority of participants had the haemoglobin (Hb)SS form of sickle cell disease.Three trials compared regular red cell transfusions to standard care in primary prevention of stroke: two in children with no previous long-term transfusions; and one in children and adolescents on long-term transfusion.Two trials compared the drug hydroxyurea (hydroxycarbamide) and phlebotomy to long-term transfusions and iron chelation therapy: one in primary prevention (children); and one in secondary prevention (children and adolescents).The quality of the evidence was very low to moderate across different outcomes according to GRADE methodology. This was due to the trials being at a high risk of bias due to lack of blinding, indirectness and imprecise outcome estimates. Red cell transfusions versus standard care Children with no previous long-term transfusionsLong-term transfusions probably reduce the incidence of clinical stroke in children with a higher risk of stroke (abnormal transcranial doppler velocities or previous history of silent cerebral infarct), risk ratio 0.12 (95% confidence interval 0.03 to 0.49) (two trials, 326 participants), moderate quality evidence.Long-term transfusions may: reduce the incidence of other sickle cell disease-related complications (acute chest syndrome, risk ratio 0.24 (95% confidence interval 0.12 to 0.48)) (two trials, 326 participants); increase quality of life (difference estimate -0.54, 95% confidence interval -0.92 to -0.17) (one trial, 166 participants); but make little or no difference to IQ scores (least square mean: 1.7, standard error 95% confidence interval -1.1 to 4.4) (one trial, 166 participants), low quality evidence.We are very uncertain whether long-term transfusions: reduce the risk of transient ischaemic attacks, Peto odds ratio 0.13 (95% confidence interval 0.01 to 2.11) (two trials, 323 participants); have any effect on all-cause mortality, no deaths reported (two trials, 326 participants); or increase the risk of alloimmunisation, risk ratio 3.16 (95% confidence interval 0.18 to 57.17) (one trial, 121 participants), very low quality evidence. Children and adolescents with previous long-term transfusions (one trial, 79 participants)We are very uncertain whether continuing long-term transfusions reduces the incidence of: stroke, risk ratio 0.22 (95% confidence interval 0.01 to 4.35); or all-cause mortality, Peto odds ratio 8.00 (95% confidence interval 0.16 to 404.12), very low quality evidence.Several review outcomes were only reported in one trial arm (sickle cell disease-related complications, alloimmunisation, transient ischaemic attacks).The trial did not report neurological impairment, or quality of life. Hydroxyurea and phlebotomy versus red cell transfusions and chelationNeither trial reported on neurological impairment, alloimmunisation, or quality of life. Primary prevention, children (one trial, 121 participants)Switching to hydroxyurea and phlebotomy may have little or no effect on liver iron concentrations, mean difference -1.80 mg Fe/g dry-weight liver (95% confidence interval -5.16 to 1.56), low quality evidence.We are very uncertain whether switching to hydroxyurea and phlebotomy has any effect on: risk of stroke (no strokes); all-cause mortality (no deaths); transient ischaemic attacks, risk ratio 1.02 (95% confidence interval 0.21 to 4.84); or other sickle cell disease-related complications (acute chest syndrome, risk ratio 2.03 (95% confidence interval 0.39 to 10.69)), very low quality evidence. Secondary prevention, children and adolescents (one trial, 133 participants)Switching to hydroxyurea and phlebotomy may: increase the risk of sickle cell disease-related serious adverse events, risk ratio 3.10 (95% confidence interval 1.42 to 6.75); but have little or no effect on median liver iron concentrations (hydroxyurea, 17.3 mg Fe/g dry-weight liver (interquartile range 10.0 to 30.6)); transfusion 17.3 mg Fe/g dry-weight liver (interquartile range 8.8 to 30.7), low quality evidence.We are very uncertain whether switching to hydroxyurea and phlebotomy: increases the risk of stroke, risk ratio 14.78 (95% confidence interval 0.86 to 253.66); or has any effect on all-cause mortality, Peto odds ratio 0.98 (95% confidence interval 0.06 to 15.92); or transient ischaemic attacks, risk ratio 0.66 (95% confidence interval 0.25 to 1.74), very low quality evidence.

AUTHORS' CONCLUSIONS

There is no evidence for managing adults, or children who do not have HbSS sickle cell disease.In children who are at higher risk of stroke and have not had previous long-term transfusions, there is moderate quality evidence that long-term red cell transfusions reduce the risk of stroke, and low quality evidence they also reduce the risk of other sickle cell disease-related complications.In primary and secondary prevention of stroke there is low quality evidence that switching to hydroxyurea with phlebotomy has little or no effect on the liver iron concentration.In secondary prevention of stroke there is low-quality evidence that switching to hydroxyurea with phlebotomy increases the risk of sickle cell disease-related events.All other evidence in this review is of very low quality.

Blood transfusion for preventing primary and secondary stroke in people with sickle cell disease

BACKGROUND

In sickle cell disease, a common inherited haemoglobin disorder, abnormal haemoglobin distorts red blood cells, causing anaemia, vaso-occlusion and dysfunction in most body organs. Without intervention, stroke affects around 10% of children with sickle cell anaemia (HbSS) and recurrence is likely. Chronic blood transfusion dilutes the sickled red blood cells, reducing the risk of vaso-occlusion and stroke. However, side effects can be severe.

OBJECTIVES

To assess risks and benefits of chronic blood transfusion regimens in people with sickle cell disease to prevent first stroke or recurrences.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register, comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and conference proceedings.Date of the latest search of the Group's Haemoglobinopathies Trials Register: 28 January 2013.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials comparing blood transfusion as prophylaxis for stroke in people with sickle cell disease to alternative or no treatment.

DATA COLLECTION AND ANALYSIS

Both authors independently assessed the risk of bias of the included trials and extracted data.

MAIN RESULTS

Searches identified three eligible randomised trials (n = 342). The first two trials addressed the use of chronic transfusion to prevent primary stroke; the third utilized the drug hydroxycarbamide (hydroxyurea) and phlebotomy to prevent both recurrent (secondary) stroke and iron overload in patients who had already experienced an initial stroke. In the first trial (STOP) a chronic transfusion regimen for maintaining sickle haemoglobin lower than 30% was compared with standard care in 130 children with sickle cell disease judged (through transcranial Doppler ultrasonography) as high-risk for first stroke. During the trial, 11 children in the standard care group suffered a stroke compared to one in the transfusion group, odds ratio 0.08 (95% confidence interval 0.01 to 0.66). This meant the trial was terminated early. The transfusion group had a high complications rate, including iron overload, alloimmunisation, and transfusion reactions. The second trial (STOP II) investigated risk of stroke when transfusion was stopped after at least 30 months in this population. The trial closed early due to a significant difference in risk of stroke between participants who stopped transfusion and those who continued as measured by reoccurrence of abnormal velocities on Doppler examination or the occurrence of overt stroke in the group that stopped transfusion. The third trial (SWiTCH) was a non-inferiority trial comparing transfusion and iron chelation (standard management) with hydroxyurea and phlebotomy (alternative treatment) with the combination endpoint of prevention of stroke recurrence and reduction of iron overload. This trial was stopped early after enrolment and follow up of 133 children because of analysis showing futility in reaching the composite primary endpoint. The stroke rate (seven strokes on hydroxyurea and phlebotomy, none on transfusion and chelation, odds ratio 16.49 (95% confidence interval 0.92 to 294.84)) was within the non-inferiority margin, but the liver iron content was not better in the alternative arm.

AUTHORS' CONCLUSIONS

The STOP trial demonstrated a significantly reduced risk of stroke in participants with abnormal transcranial Doppler ultrasonography velocities receiving regular blood transfusions. The follow-up trial (STOP 2) indicated that individuals may revert to former risk status if transfusion is discontinued. The degree of risk must be balanced against the burden of chronic transfusions. The combination of hydroxyurea and phlebotomy is not as effective as "standard" transfusion and chelation in preventing secondary stroke and iron overload. Ongoing multicentre trials are investigating the use of chronic transfusion to prevent silent infarcts, the use of hydroxyurea as an alternative to transfusion in children with abnormal transcranial Doppler ultrasonography velocities, and the use of hydroxyurea to prevent conversion of transcranial Doppler ultrasonography velocities from conditional (borderline) to abnormal values.

Cerebral blood flow abnormalities in children with sickle cell disease: a systematic review

A systematic review was performed to assess whether cerebral blood flow with different imaging modalities could identify brain abnormalities in children with sickle cell disease where structural magnetic resonance imaging and transcranial Doppler velocity appeared normal. A total of 11 studies were identified which reported cerebral blood flow abnormalities alongside structural magnetic resonance imaging or transcranial Doppler velocity abnormalities in patients with sickle cell disease. Potential for bias was assessed with the quality assessment of diagnostic accuracy studies scale in addition to treatment bias. Subjects of each study were categorized into patients with and without stroke. The prevalence of abnormalities for each modality was then separately calculated in each group. The included studies had mostly moderate degrees of bias. The prevalence of blood flow abnormalities compared with structural magnetic resonance imaging abnormalities was equal to or lower in patients with stroke and equal to or greater in patients without stroke. Blood flow abnormalities were more prevalent than transcranial Doppler abnormalities in four studies of patients without stroke and in one study of patients with stroke. The studies suggest that the assessment of cerebral blood flow in sickle cell disease can be of potential value in addressing brain abnormalities at the tissue level; however, further studies are warranted.

Cerebral tissue hemoglobin saturation in children with sickle cell disease

BACKGROUND

Desaturation of hemoglobin (Hb) in cerebral tissue, a physiologic marker of brain vulnerable to ischemic injury, can be detected non-invasively by transcranial oximetry. Absolute cerebral oximetry has not been studied in sickle cell disease (SCD), a group at very high risk of cerebral infarction in whom prevention of brain injury is key.

PROCEDURE

We measured absolute Hb saturation in cerebral tissue (S(CT)O(2)) in children with SCD using near-infrared spectrophotometry and investigated the contributions of peripheral Hb saturation (S(P)O(2)), hematologic measures, cerebral arterial blood flow velocity, and cerebral arterial stenosis to S(CT)O(2). We also assessed the effects of transfusion.

RESULTS

We studied 149 children with SCD (112 HbSS/Sβ(0); 37 HbSC/Sβ(+)). S(CT)O(2) was abnormally low in 75% of HbSS/Sβ(0) and 35% of HbSC/Sβ(+) patients. S(CT)O(2) (mean ± SD) was 53.2 ± 14.2 in HbSS/Sβ(0) and 66.1 ± 9.2% in SC/Sβ(+) patients. S(CT)O(2) correlated with age, sex, Hb concentration, reticulocytes, Hb F, and S(P)O(2), but not transcranial Doppler arterial blood flow velocities as continuous measures. In multivariable models, S(P)O(2), Hb concentration, and age were significant independent determinants of S(CT)O(2). Cerebral vasculopathy was associated with ipsilateral cerebral desaturation. Transfusion increased S(CT)O(2) and minimized the inter-hemispheric differences in S(CT)O(2) due to vasculopathy.

CONCLUSIONS

Cerebral desaturation, a physiologic marker of at-risk brain, is common in SCD, more severe in HbSS/Sβ(0) patients, and associated with peripheral desaturation, more severe anemia, and increasing age. Cerebral oximetry has the potential to improve the identification of children with SCD at highest risk of neurologic injury and possibly serve as a physiologic guide for neuroprotective therapy.

Haematological values in homozygous sickle cell disease in steady state and haemoglobin phenotypes AA controls in Lagos, Nigeria

BACKGROUND

Sickle cell disease is a genetic abnormality involving the haemoglobin. Although, it is primarily a red cell disorders, the white blood cells and platelets are also affected by the mutation. The consequent haemoglobin S causes polymerization of haemoglobin resulting in haemolysis and anaemia. This study aims to provide baseline haematological values in sickle cell disease patients in steady state and compare the deviation from haemoglobin phenotype AA control values.

METHODS

A case-control study was conducted amongst homozygous sickle cell patients attending the sickle cell clinics of Lagos State University Teaching Hospital Ikeja and haemoglobin phenotype AA controls. About 4.5mls of blood sample was collected from each participant for full blood count analysis. All blood samples were screened for HIV and haemoglobin phenotypes confirmed using cellulose acetate haemoglobin electrophoresis at pH 8.6.

RESULTS

A total of 103 cases and 98 controls were enrolled. The overall mean haemoglobin concentration for cases was 7.93 ± 1.47 g/dl, packed cell volume 24.44 ± 4.68%, mean cell volume 81.52 ± 7.89 fl, and mean cell haemoglobin 26.50 ± 3.20 pg. While for controls, mean haemoglobin concentration was 13.83 ± 1.32 g/dl, packed cell volume 43.07 ± 3.95%, mean cell volume 86.90 ± 4.69 fl, and mean cell haemoglobin 28.50 ± 1.34 pg. The overall mean white blood cell counts for the cases was 10.27 ± 3.94 *103/μl and platelet counts of 412.71 ± 145.09*103/μl. While white blood cell count for the controls was 5.67 ± 1.59*103/μl and platelet counts of 222.82 ± 57.62*103/μl.

CONCLUSION

Homozygous sickle cell disease patients have lower values of red cell parameters, but higher values of white cell and platelets counts compared to haemoglobin phenotype AA controls.

Hematology and Oncology in Critical Illness

This chapter will focus on a variety of hematologic issues pertinent to the care of critically ill children. This is an area of intense research with the pathophysiology underlying these clinical conditions becoming progressively better understood. This improved understanding has resulted in new therapeutic strategies that are being assessed in multicenter clinical trials. The chapter will begin by describing the incidence and pathophysiologic significance of anemia in the pediatric intensive care unit (PICU) providing a differential diagnosis of the many conditions that may present with anemia in this setting. The chapter will next consider disseminated intravascular coagulation (DIC) focusing on the pathophysiology of a condition that has been associated with much morbidity and mortality. The underlying conditions predisposing to DIC will be detailed as well as a number of treatment options that have been implemented in clinical trials. In addition to DIC, thrombocytopenia may be caused by a number of other clinical conditions important to the pediatric critical care provider. The clinical and prognostic significance of thrombocytopenia will be addressed and a focused differential diagnosis will be provided. Thrombotic disorders are becoming increasingly recognized in children and are a particular concern for the pediatric intensivist. The epidemiology of thromboembolism in children will be reviewed focusing on the conditions most commonly associated with these thromboses. Finally, a chapter on hematologic issues in the critically ill child would not be complete without a discussion of sickle cell disease. Acute chest syndrome, one of the most frequent complications of sickle cell disease resulting in the need for intensive care services, will be discussed in detail.

Aggregation of mononuclear and red blood cells through an {alpha}4{beta}1-Lu/basal cell adhesion molecule interaction in sickle cell disease

BACKGROUND

Abnormal interactions between red blood cells, leukocytes and endothelial cells play a critical role in the occurrence of the painful vaso-occlusive crises associated with sickle cell disease. We investigated the interaction between circulating leukocytes and red blood cells which could lead to aggregate formation, enhancing the incidence of vaso-occlusive crises.

DESIGN AND METHODS

Blood samples from patients with sickle cell disease (n=25) and healthy subjects (n=5) were analyzed by imaging and classical flow cytometry after density gradient separation. The identity of the cells in the peripheral blood mononuclear cell layer was determined using antibodies directed specifically against white (anti-CD45) or red (anti-glycophorin A) blood cells.

RESULTS

Aggregates between red blood cells and peripheral blood mononuclear cells were visualized in whole blood from patients with sickle cell disease. The aggregation rate was 10-fold higher in these patients than in control subjects. Both mature red blood cells and reticulocytes were involved in these aggregates through their interaction with mononuclear cells, mainly with monocytes. The size of the aggregates was variable, with one mononuclear cell binding to one, two or several red blood cells. Erythroid Lu/basal cell adhesion molecule and α(4)β(1) integrin were involved in aggregate formation. The aggregation rate was lower in patients treated with hydroxycarbamide than in untreated patients.

CONCLUSIONS

Our study gives visual evidence of the existence of circulating red blood cell-peripheral blood mononuclear cell aggregates in patients with sickle cell disease and shows that these aggregates are decreased during hydroxycarbamide treatment. Our results strongly suggest that erythroid Lu/basal cell adhesion molecule proteins are implicated in these aggregates through their interaction with α(4)β(1) integrin on peripheral blood mononuclear cells.

Skull bone infarctive crisis and deep vein thrombosis in homozygous sickle cell disease- case report and review of the literature

Here we describe an 8-year old male child with homozygous sickle cell disease who presented with left parietal skull bone infarction and, during his stay in hospital, developed a right femoral deep vein thrombosis (DVT), both uncommon complications of the disease. He initially presented with severe headache and generalised tenderness of the calvarium, which did not respond to simple analgesics. Scalp swelling in and around the left frontal (including left orbit) and parietal regions developed 24 h after presentation. The differential diagnosis included incipient stroke, acute sickle bone crisis and osteomyelitis, with a possible complication of epidural haematoma, or orbital compression syndrome. An initial exchange blood transfusion did not lead to appreciable reduction in opiate requirements. Significant symptomatic relief was attained only after a second exchange transfusion. The DVT developed at the site of catheterisation (right femoral vein), and this was treated with maximal doses of enoxaparin followed by warfarin. The child is now well and off anti-coagulants. In this article we present a review of the literature and discuss possible mechanisms of these complications in our patient.

Overt and Incomplete (Silent) Cerebral Infarction in Sickle Cell Anemia: Diagnosis and Management

Cerebral vasculopathy in sickle cell anemia (HbSS) is manifest clinically as cerebral infarction and intracranial hemorrhage. The type of stroke, ischemic or hemorrhagic, is age specific with distinct differences in outcomes. Cerebral infarction with or without clinical stroke begins during early childhood and rarely causes death immediately.

Overt and Incomplete (Silent) Cerebral Infarction in Sickle Cell Anemia: Diagnosis and Management

Regional complete infarctions in children with sickle cell anemia (HbSS) are often associated with stenosis of the large intracranial arteries and result in lifetime disability. Incomplete infarction occurs more frequently than previously recognized and has far-reaching effects on neurocognitive development and the risk for overt secondary strokes into adulthood. Clinical and neuroimaging modalities have been highlighted in an algorithmic approach, with the studies giving the highest yield in results and most likely to be available listed in sequential order. The recognition of an emerging "second peak" incidence in the third decade of life is worrisome and warrants more intense scrutiny and diagnosis of subtle findings of stroke in this young adult population.

Psychological complications in sickle cell disease

This review examines the evidence for some of the common psychological complications found across the life span of patients with sickle cell disease (SCD), which are likely to be encountered by haematologists responsible for their medical management. Electronic searches of medical and psychological databases were conducted with a focus on three main areas: psychological coping, quality of life and neuropsychology. Psychological complications were identified in both children and adults with SCD, and included inappropriate pain coping strategies; reduced quality of life owing to restrictions in daily functioning, anxiety and depression; and neurocognitive impairment. There were wide variations in design and consistency of the studies, therefore, some caution needs to be observed in the findings. Moreover, interventional studies were lacking in some areas such as neuropsychology. Utilization of psychological interventions including patient education, cognitive behavioural therapy, and special educational support to help improve the quality of life of patients are recommended.

Blood mononuclear cells and platelets have abnormal fatty acid composition in homozygous sickle cell disease

Leukocyte adhesion to vascular endothelium contributes to vaso-occlusion and widespread organ damage in sickle cell disease (SCD). Previously, we found high expression of the adhesion molecules alphaMbeta2 integrin and L-selectin in HbSS individuals with severe disease. Since membrane n-6 and n-3 polyunsaturated fatty acids modulate cell adhesion, inflammation, aggregation and vascular tone, we investigated the fatty acid composition of mononuclear cells (MNC) and platelets of HbSS patients in steady state (n=28) and racially matched, healthy HbAA controls with similar age and sex distribution living in the same environment (n=13). MNC phospholipids of the patients had lower levels of docosahexaenoic acid (DHA, p<0.01) and increased arachidonic acid (AA, p<0.005) relative to HbAA controls. Similarly, platelets from HbSS patients had less eicosapentaenoic acid (EPA, p<0.05) and more AA (p<0.05) in choline phosphoglycerides (CPG), with reduced DHA (p<0.05) in ethanolamine phosphoglycerides. Platelet CPG had lower DHA levels in SCD patients with complications compared to those without (p<0.05). Reduced cell content of EPA and DHA relative to AA favours the production of aggregatory and proinflammatory eicosanoids that activate leukocytes and platelets. This facilitates inflammation, leukocyte adhesion, platelet aggregation and vaso-occlusion in SCD.

Coexisting Systemic Lupus Erythematosus and Sickle Cell Disease

Systemic lupus erythematosus (SLE) and sickle cell disease (SCD) are relatively common disorders with comparable prevalence among blacks. The coexistence of these 2 conditions in the same individual appears to be rare. We report 4 cases of coexisting SLE and SCD. These patients displayed a broad spectrum of musculoskeletal, central nervous system, and renal complications that may be associated with either SCD or SLE. Because of a substantial overlap between the clinical manifestations of these 2 disorders, the diagnosis of SLE in patients with SCD may be difficult to establish and is often delayed. Up to 23% of patients with SCD may have antinuclear antibodies. All patients in this series had antecedent SCD but new important complications from SLE.

The intriguing contribution of white blood cells to sickle cell disease - a red cell disorder

Sickle cell disease (SCD) is characterized by a point mutation that replaces adenine with thymidine in the sixth codon of the beta-globin gene, a unique morphological abnormality of red blood cells, vaso-occlusion with ischaemic tissue injury, and susceptibility to infections. Vascular lumen obstruction in SCD results from interaction of erythrocytes, leukocytes, platelets, plasma proteins, and the vessel wall. The disease phenotype is a product of various genes and environmental factors acting in concert with the protein lesion underlying the red cell anomaly. The severity of SCD increases with leukocyte count. The biological basis and therapeutic implications of this relationship are discussed. Leukocytes contribute to SCD by adhering to blood vessel walls and obstructing the lumen, aggregating with other blood cells with more effective blockage of the lumen, stimulating the vascular endothelium to increase its expression of ligands for adhesion molecules on blood cells, and causing tissue damage and inflammatory reaction which predispose to vaso-occlusion. Patients with impaired ability of leukocytes to kill microbes are more prone to infections; which precipitate sickle cell crisis. Reduction of leukocyte count ameliorates SCD. Similarly, targeted blockade or reduced synthesis of specific leukocyte adhesion molecules and their ligands might confer clinical benefit in SCD.

Relationship between the clinical manifestations of sickle cell disease and the expression of adhesion molecules on white blood cells

BACKGROUND

The severity of sickle cell disease (SCD) increases with leukocyte count. The biological basis could be that leukocyte adherence to vascular endothelium mediated by adhesion molecules (AMs) facilitates vaso-occlusion, the basic pathological process in SCD.

OBJECTIVE

To find out if there is a relationship between expression of AMs by leukocytes and the clinical manifestations of SCD.

METHODS

Flow cytometry was used to study the relationship between leukocyte AM expression and disease manifestations in 100 patients with homozygous (HbSS) sickle cell disease and 34 genotype HbAA controls. The effect of hydroxyurea therapy on AM expression was also examined. We excluded HbSS patients with any other disease, pregnancy in the previous 3 months, or Haemogloben F (HbF) > or = 10%.

RESULTS

Patients with complications of SCD showed high expression of alphaMbeta integrin by the neutrophils; and l-selectin by lymphocytes and neutrophils (P < 0.03). CD18 was highly expressed by neutrophils in patients with sickle nephropathy (P = 0.018), and l-selectin by lymphocytes in those with stroke (P = 0.03). Monocyte l-selectin increased in sickle cell crisis relative to steady state (P = 0.04). Expression of alphaLbeta2 integrin by neutrophils, monocytes, and lymphocytes decreased within a month of hydroxyurea therapy (P < 0.05), with symptomatic improvement in the patients and no more than 3.3% rise in HbF level.

CONCLUSIONS

The findings suggest that in SCD (1): High steady-state expression of alphaMbeta2 integrin and l-selectin by leukocytes predisposes to severe manifestations. (2) Increased leukocyte AM expression above steady-state levels could be important in the genesis of crisis. (3) The early symptomatic improvement that follows hydroxyurea therapy is mediated via mechanisms independent of increased HbF, and may involve reduced AM expression in leukocytes. (4) Other treatment modalities that reduce leukocyte AM expression might also confer clinical benefit.

Sickle cell disease: the neurological complications

The genetic cause of sickle cell disease has been known for decades, yet the reasons for its clinical variability are not fully understood. The neurological complications result from one point mutation that causes vasculopathy of both large and small vessels. Anemia and the resultant cerebral hyperemia produce conditions of hemodynamic insufficiency. Sickled cells adhere to the endothelium, contributing to a cascade of activated inflammatory cells and clotting factors, which result in a nidus for thrombus formation. Because the cerebrovascular reserve becomes exhausted, the capacity for compensatory cerebral mechanisms is severely limited. There is evidence of small-vessel sludging, and a relative deficiency of nitric oxide in these vessels further reduces compensatory vasodilatation. Both clinical strokes and silent infarcts occur, affecting motor and cognitive function. New data suggest that, in addition to sickle cell disease, other factors, both environmental (eg, hypoxia and inflammation) and genetic (eg, mutations resulting in thrombogenesis), may contribute to a patient's stroke risk. The stroke risk is polygenic, and sickle cell disease can be considered a model for all cerebrovascular disease. This complex disease underscores the potential intellectual and practical distance between the determination of molecular genetics and effective clinical application and therapeutics.

Arterial ischemic stroke in childhood: the role of plasma-phase risk factors

The role of plasma-phase risk factors for stroke in the pediatric age group is presently unclear due to the lack of sufficiently large prospective studies, and due to the fact that these risk factors do not apply uniformly to newborns, children with sickle cell disease, and older children. Available evidence indicates that factor V Leiden, prothrombin 20210A, and lipoprotein (a) are all important in the pathogenesis of arterial ischemic stroke in older children, but the role of other plasma-phase risk factors remains uncertain. The contribution of these risk factors to newborn stroke and the stroke of children with sickle cell disease is similarly unclear, likely because the ischemia in affected children is predominantly due to nonhematologic perinatal events and erythrocyte adhesion to endothelium with obstruction of flow in the cerebral microcirculation, respectively. Evaluation of childhood stroke should, in our view, always be performed from the standpoint of the presenting clinical symptoms, diagnostic imaging, and determination of plasma-phase risk factors. Therapeutic anticoagulation and use of antiplatelet agents at present focus on the older child.

Blood transfusion for preventing stroke in people with sickle cell disease

BACKGROUND

Sickle cell disease is a common inherited haemoglobin disorder. The abnormal haemoglobin causes distortion of red blood cells, anaemia, vaso-occlusion and dysfunction in virtually any organ system in the body. Stroke occurs in around 10% of children with sickle cell anaemia, and recurrences after a first stroke are likely. Chronic blood transfusion regimes are often used in an attempt to dilute the sickled red blood cells, thus reducing the risk of vaso-occlusion and stroke. However, the side-effects of such regimens can be severe.

OBJECTIVES

To assess the relative risks and benefits of chronic blood transfusion regimes in patients with sickle cell disease to prevent a first stroke or further strokes.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group specialist register which comprises references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings. Date of the most recent search of the Group's specialised register: July 2001

SELECTION CRITERIA

All those randomised or quasi-randomised controlled trials in which blood transfusion as a preventative measure for stroke in patients with sickle cell disease are compared to an alternative treatment or to no treatment.

DATA COLLECTION AND ANALYSIS

Both reviewers independently assessed trial quality and extracted data from the study included.

MAIN RESULTS

One trial was identified by the initial search and this met the inclusion criteria for the review. The trial compared a chronic transfusion regime to maintain sickle haemoglobin at less than 30% with standard care in 130 children with sickle cell disease who were judged to be at high risk of a first stroke through transcranial doppler ultrasonography. Eleven children in the standard care group suffered a stroke during the trial, compared to only one in the transfusion group. Because of this 92% relative risk reduction, the trial was terminated 16 months early. It had been planned that all patients would be treated for 30 months, but median follow-up only 21.1 months. However, a high rate of complications such as iron overload, alloimmunisation and transfusion reactions were seen in the children who were receiving transfusions. No randomised controlled trials were identified which investigated use of transfusion for preventing recurrence of stroke.

REVIEWER'S CONCLUSIONS

While the included study demonstrated a significantly reduced risk of stroke in patients receiving regular blood transfusions, the degree of risk must be balanced against the burden of a chronic transfusion regime. Further research is required to establish the use of transfusion in preventing secondary stroke, the age, or length of time after an event, at which transfusion can safely be stopped, and to further define risk factors for stroke in order to reduce the chance of unnecessarily putting children onto a chronic transfusion regime.

Sickle cell anaemia: progress in pathogenesis and treatment

The phenotypic expression of sickle cell anaemia varies greatly among patients and longitudinally in the same patient. It influences all aspects of the life of affected individuals including social interactions, intimate relationships, family relations, peer interactions, education, employment, spirituality and religiosity. The clinical manifestations of sickle cell anaemia are protean and fall into three major categories: anaemia and its sequelae;pain and related issues; andorgan failure including infection. Recent studies on the pathogenesis of sickle cell anaemia have centred on the sequence of events that occur between polymerisation of deoxy haemoglobin (Hb) S and vaso-occlusion. Cellular dehydration, inflammatory response and reperfusion injury seem to be important pathophysiological mechanisms. Management of sickle cell anaemia continues to be primarily palliative in nature, including supportive, symptomatic and preventative approaches to therapy. Empowerment and education are the major aspects of supportive care. Symptomatic management includes pain management, blood transfusion and treatment of organ failure. Pain managment should follow certain priniciples that include assessment, individualisation of therapy and proper utilisation of opioid and nonopioid analgesics in order to acheive adequate pain relief. Blood selected for transfusion should be leuko-reduced and phenotypically matched for the C, E and Kell antigens. Exchange transfusion is indicated in patients who are transfused chronically in order to prevent or delay the onset of iron-overload. Acute chest syndrome is the most common form of organ failure and its management should be agressive, including adequate ventilation, multiple antibacterials and simple or exchange blood transfusion depending on its severity. Preventitive therapy includes prophylactic penicillin in infants and children, blood transfusion (preferably exchange transfusion) in patients with stroke, and hydroxyurea in patients with frequent acute painful episodes. Bone marrow and cord blood transplantation have been successful modalities of curative therapy in selected children with sickle cell anaemia. Newer approaches to preventative therapy include cellular rehydration with agents that inhibit the Gardos channel or the KCl co-transport channel. Curative gene therapy continues to be investigational at the level of the test tube and transgenic mouse models.

Stroke in hemoglobin (SD) sickle cell disease with moyamoya: successful hydroxyurea treatment after cerebrovascular bypass surgery

An 11-year-old boy with hemoglobin sickle disease (HbSD), bilateral stenosis of the intracranial carotid arteries, and moyamoya syndrome had recurrent ischemic strokes with aphasia and right hemiparesis. His parents (Jehovah's Witnesses) refused blood transfusions. After bilateral extracranial-intracranial (EC-IC) bypass surgery, hydroxyurea treatment increased hemoglobin F (HbF) levels to more than 30%. During a follow-up of 28 months, flow velocities in the basal cerebral arteries remained stable, neurologic sequelae regressed, and ischemic events did not recur. This is the first report of successful hydroxyurea treatment after bypass surgery for intracranial cerebral artery obstruction with moyamoya syndrome in sickle cell disease. The patient's religious background contributed to an ethically challenging therapeutic task. (Blood. 2001;97:2165-2167)