Nocturnal hypoxaemia and central-nervous-system events in sickle-cell disease

Updates in Pediatric Sickle Cell Lung Disease

Sickle cell lung disease presents a challenging care paradigm involving acute and chronic lower airway disease, sleep-disordered breathing, pulmonary vascular disease, and modification by environmental factors. Understanding the presentation, pathophysiology, and diagnostic approaches is essential for accurate identification and management. While significant progress has been made, there remains a need for research to develop effective treatments and interventions to decrease disease burden in these children. Additionally, the long-term impact of interventions on cardiopulmonary outcomes is unknown. Collaborative efforts among health care providers, researchers, advocacy groups, and policy makers are crucial to improving the lives of children with SCD.

Nocturnal hypoxaemia is common in adults with sickle cell anaemia

The symptoms and sequelae of sickle cell anaemia (SCA) are caused by the polymerization of deoxygenated sickle haemoglobin, and people with SCA may be uniquely susceptible to adverse outcomes from hypoxia and haemoglobin desaturation. We examined by oximetry adults (aged 18-45 years) with SCA presenting symptoms indicative of polysomnography, at a single institution, irrespective of treatment, for nocturnal hypoxaemia. Clinical labs and blood for in vitro assessments were taken upon enrolment and after 8-12 weeks of oxygen therapy or observation. Of 21 screened participants, nine (43%) had sufficient nocturnal hypoxaemia to warrant oxygen therapy (≥5 min at SpO2 ≤ 88%). Time spent at SpO2 ≤ 88% associated with age (p = 0.0092), annual hospitalizations (p = 0.0018) and anaemia (p = 0.0139), as well as plasma levels of TNFα (p = 0.0019) and IL-4 (p = 0.0147). Longitudinal analysis showed that WBC significantly decreased during the follow-up period in hypoxic individuals but not in non-hypoxic individuals (p = 0.0361 and p = 0.6969 respectively). Plasma levels of CCL2 and IL-1ra tended to increase, while levels of red blood cell reactive oxygen species tended to decrease with oxygen therapy. Overall, nocturnal hypoxaemia was common in this pilot study population and associated with plausible clinical comorbidities; oxygen therapy may decrease inflammation and oxidative damage in hypoxic individuals.

The Cardiopulmonary Complications of Sickle Cell Disease

Sickle cell disease (SCD) is a genetic hemoglobinopathy associated with extensive morbidity and early mortality. While there have been recent improvements in available disease-modifying therapies for SCD, cardiopulmonary complications remain a major risk factor for death in this population. We provide an overview of current knowledge regarding several of the major acute and chronic cardiopulmonary complications in SCD, including: acute chest syndrome, airway disease, lung function abnormalities, nocturnal hypoxemia and sleep disordered breathing, pulmonary vascular disease, and sickle cell cardiomyopathy.

The association between sleep disturbances and neurocognitive function in pediatric sickle cell disease

BACKGROUND AND OBJECTIVE

Youth with sickle cell disease (SCD) without neurological complications continue to be at increased risk of neurocognitive difficulties. Nocturnal hypoxemia is associated with neurocognitive outcomes and has been identified as a chronic complication in youth with SCD. The objective of this study was to assess the relationship between sleep disturbances and neurocognitive functioning in youth with SCD, while taking into account demographic and socioeconomic factors.

METHODS

Youth with SCD were identified through retrospective chart review who underwent a standardized polysomnography (PSG) and completed a neuropsychological testing battery to assess cognitive skills, including verbal comprehension, working memory, processing speed, and cognitive flexibility. Questionnaires were also collected to assess parent-reported concerns with their youth's executive and adaptive skills.

RESULTS

Twenty-seven youth with SCD, ages 6-17, were identified who completed both a PSG and neuropsychological testing. Results demonstrated that verbal comprehension decreased by 2.37 standard points for every unit decrease in mean nocturnal oxygen saturation (SpO2) (p = 0.031). Working memory was also found to decrease by 1.46 standard points for each 1% increase in time spent under 90% oxygen saturation (pTST SpO2 < 90%) (p = 0.030). Sleep parameters did not significantly predict other cognitive scores or parent-reported executive or behavioral ratings.

CONCLUSION

Our study found that sleep disturbance, mean nocturnal SpO2 and pTST SpO2 < 90%, significantly affected verbal comprehension and working memory performance, respectively. Overall, these findings have the potential to identify sleep needs in youth with SCD to promote sleep-targeted interventions as a modifiable factor to reduce neurocognitive deficits.

Association of laboratory markers and cerebral blood flow among sickle cell anemia children

BACKGROUND

Stroke is one of the highest complications of sickle-cell anemia (SCA). The Transcranial Doppler (TCD) has been adopted worldwide as a gold standard method for detecting alterations in the blood velocity in cerebral arteries. In this study, we investigated the association between laboratory parameters and increased cerebral blood flow velocity in Brazilian SCA pediatric patients.

METHODS

The study included 159 pediatric patients with SCA, submitted to TCD velocity screening, and the time-averaged maximum mean velocity (TAMMV) was determined in the middle cerebral artery (MCA), anterior cerebral artery (ACA), and distal intracranial internal carotid artery (ICA). We compared cerebral blood flow in patients stratified by the following: TCD1-defined as normal, with TAMMV inferior to 170 cm/s; TCD2-conditional, with TAMMV above 170 cm/s, but less than 199 cm/s; TCD3-altered, with TAMMV greater than or equal to 200 cm/s.

RESULTS

TAMMV was negatively correlated with age and weight (p < 0.05). Moreover, TAMMV was associated or correlated with reductions in HbF, RBC, hemoglobin, hematocrit, HDL, and haptoglobin and, increases in MCV, MCH, RDW, reticulocytes, WBC, lymphocytes, monocytes, eosinophils, total and indirect bilirubin, LDH, AST, ALT, glucose, ferritin, and AAT (p < 0.05).

CONCLUSION

The current study highlights the importance of the investigation of hemolytic and inflammatory biomarkers for monitoring the clinical outcome of SCA pediatric patients, to avoid acute or chronic stroke. Moreover, glucose and HDL-C appear useful for predicting higher TAMMV.

The burden of sleep disordered breathing in children with sickle cell disease

Children with sickle cell disease (SCD) have an increased risk of sleep disordered breathing (SDB) compared with the general pediatric population. There has been a growing research interest on this field in recent years, yet many questions regarding risk factors and clinical implications of SDB remain unclear. The aim of this review is to provide a concise narrative and systematic synthesis of the available evidence on the epidemiology, clinical presentation, complications, and management, of SDB in children with SCD. An electronic search was conducted on studies published from the 1st of January 2000 to the 31st of December 2020 in PubMed/Medline, Scopus, and Cochrane databases. All studies focusing on SDB in children with SCD aged from 0 to 20 years were included. Studies were eligible for inclusion if available in the English language. A quantitative synthesis of the included studies was performed. Only studies focusing on specific treatment outcomes were included in a meta-analytic process. A total of 190 papers were initially identified. After screening the title and abstract, 112 articles were evaluated for eligibility. At the end of the selection process, 62 studies were included in the analysis. Sleep disordered breathing is associated with worse neurological, neurocognitive, and cardiological outcomes, whereas the association with frequency or severity of vaso-occlusive pain events and acute chest syndrome was not clarified. Therapeutic interventions like adenotonsillectomy or oxygen supplementation may result in a significant increase in mean nocturnal oxygen saturation but effective clinical implications remain still unclear.

The association between obstructive sleep apnea and stroke in sickle-cell disease children

INTRODUCTION

The prevalence of stroke in SCD patients was reported to be around 4%; however, the pediatric category was among the higher risk group for stroke compared to young and middle age adults. Furthermore, the risk of OSA increases in SCD children. The objective of this study is to calculate the prevalence of stroke in children with SCD with and without obstructive sleep apnea.

METHOD

This is a cross-sectional study held at two major tertiary hospitals in Jeddah, Saudi Arabia. Inclusion criteria included patients aged between 2 and 18 at the time of enrollment with confirmed SCD. The primary outcome of the study was at least one documented episode of stroke over the last 3 years. OSA was assessed using PSQ.

RESULTS

A total of 150 children with SCD were included in the study. The mean age was 9.6 (±4.3). Most of the sample (85.3%) were sickle-cell anemia with HbSS. Children who were positive for OSA were at higher odds of having a stroke [OR 2.97; 95% CI 1.13-7.75 (P = 0.02)]. The relationship between OSA and stroke was not significant in the multivariant analysis.

CONCLUSION

Patients who had OSA had a higher prevalence of stroke compared to non-OSA patients by 16% with almost three times higher odds. The difference was statistically significant in bivariant but not multivariant analysis. The rate of hospitalization, emergency visit, and blood transfusion were not affected by OSA status. Screening for OSA in high-risk patients such as SCD children and early management could prevent the risk of SCD complications.

Study of montelukast in children with sickle cell disease (SMILES): a study protocol for a randomised controlled trial

Background

Young children with sickle cell anaemia (SCA) often have slowed processing speed associated with reduced brain white matter integrity, low oxygen saturation, and sleep-disordered breathing (SDB), related in part to enlarged adenoids and tonsils. Common treatments for SDB include adenotonsillectomy and nocturnal continuous positive airway pressure (CPAP), but adenotonsillectomy is an invasive surgical procedure, and CPAP is rarely well-tolerated. Further, there is no current consensus on the ability of these treatments to improve cognitive function. Several double-blind, randomised controlled trials (RCTs) have demonstrated the efficacy of montelukast, a safe, well-tolerated anti-inflammatory agent, as a treatment for airway obstruction and reducing adenoid size for children who do not have SCA. However, we do not yet know whether montelukast reduces adenoid size and improves cognition function in young children with SCA.

Methods

The Study of Montelukast In Children with Sickle Cell Disease (SMILES) is a 12-week multicentre, double-blind, RCT. SMILES aims to recruit 200 paediatric patients with SCA and SDB aged 3–7.99 years to assess the extent to which montelukast can improve cognitive function (i.e. processing speed) and sleep and reduce adenoidal size and white matter damage compared to placebo. Patients will be randomised to either montelukast or placebo for 12 weeks. The primary objective of the SMILES trial is to assess the effect of montelukast on processing speed in young children with SCA. At baseline and post-treatment, we will administer a cognitive evaluation; caregivers will complete questionnaires (e.g. sleep, pain) and measures of demographics. Laboratory values will be obtained from medical records collected as part of standard care. If a family agrees, patients will undergo brain MRIs for adenoid size and other structural and haemodynamic quantitative measures at baseline and post-treatment, and we will obtain overnight oximetry.

Discussion

Findings from this study will increase our understanding of whether montelukast is an effective treatment for young children with SCA. Using cognitive testing and MRI, the SMILES trial hopes to gain critical knowledge to help develop targeted interventions to improve the outcomes of young children with SCA.

Trial registration

ClinicalTrials.govNCT04351698. Registered on April 17, 2020. European Clinical Trials Database (EudraCT No. 2017-004539-36). Registered on May 19, 2020

Epidemiology of Stroke in Sickle Cell Disease

Sickle cell disease is the most common cause of stroke in childhood, both ischaemic and haemorrhagic, and it also affects adults with the condition. Without any screening or preventative treatment, the incidence appears to fall within the range 0.5 to 0.9 per 100 patient years of observation. Newborn screening with Penicillin prophylaxis and vaccination leading to reduced bacterial infection may have reduced the incidence, alongside increasing hydroxyurea prescription. Transcranial Doppler screening and prophylactic chronic transfusion for at least an initial year has reduced the incidence of stroke by up to 10-fold in children with time averaged mean of the maximum velocity >200 cm/s. Hydroxyurea also appears to reduce the incidence of first stroke to a similar extent in the same group but the optimal dose remains controversial. The prevention of haemorrhagic stroke at all ages and ischaemic stroke in adults has not yet received the same degree of attention. Although there are fewer studies, silent cerebral infarction on magnetic resonance imaging (MRI), and other neurological conditions, including headache, epilepsy and cognitive dysfunction, are also more prevalent in sickle cell disease compared with age matched controls. Clinical, neuropsychological and quantitative MRI screening may prove useful for understanding epidemiology and aetiology.

Hydroxycarbamide treatment reduces transcranial Doppler velocity in the absence of transfusion support in children with sickle cell anaemia, elevated transcranial Doppler velocity, and cerebral vasculopathy: the EXTEND trial

EXpanding Treatment for Existing Neurological Disease (EXTEND) investigated whether hydroxycarbamide lowers transcranial Doppler (TCD) velocities in Jamaican children with sickle cell anaemia (SCA) and elevated TCD velocity with or without previous stroke. Forty-three children (age 2-17 years) with baseline maximum time-averaged mean velocity (TAMV) ≥ 170 cm/s were stratified into three risk categories based on treatment status and stroke history: Group 1 (no history of stroke, on hydroxycarbamide, n = 12); and Groups 2 (no stroke, no hydroxycarbamide, n = 21) and 3 (previous stroke, no hydroxycarbamide, n = 10). Open-label hydroxycarbamide at 20 mg/kg/day was commenced, with escalation to maximum tolerated dose (MTD) based on mild marrow suppression (average dose 25·4 ± 4·5 mg/kg/day). TCD was performed every six months with brain magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA) at baseline and after 18-months of hydroxycarbamide. The maximum TAMV decreased significantly compared to baseline (24 ± 30 cm/s, P < 0·0001), with similar declines in all groups. Clinical stroke occurred in five children, one in Group 1, none in Group 2, and four in Group 3, P = 0·0032, comparing group incidence rates. Brain MRI/MRA was stable in children without clinical stroke. EXTEND documents the feasibility and benefits of hydroxycarbamide at MTD to lower TCD velocities and reduce stroke risk in children with SCA and no history of primary stroke in low-resource settings without transfusion management.

Nocturnal hypoxemia measured by polysomnogram is associated with acute chest syndrome in pediatric sickle cell disease

STUDY OBJECTIVES

Nocturnal hypoxemia is associated with increased risk of sickle cell disease (SCD) complications. The association of nighttime hypoxemia and acute chest syndrome (ACS) in children with SCD has yet to be determined.

METHODS

This is a retrospective study of children with SCD who underwent polysomnography at a SCD center. Univariate logistic regression was used to assess the association between nocturnal hypoxemia and ACS admissions. Multivariate logistic regression was performed to verify the effects of different clinical covariates on ACS. Secondary analysis comparing patients with one vs multiple ACS admissions was performed.

RESULTS

One hundred ten individuals with SCD who completed their polysomnogram (mean age of 9.4 years) were identified. Fifty-nine (54%) had a history of at least one episode of ACS admission (mean age of 4.1 years), including 40 with multiple episodes. The percentage of total sleep time with O₂ saturation < 90% was greater in the ACS group (P < .05). Similarly, mean nocturnal O₂ saturation was lower in the ACS group (P < .0005). Mean nocturnal O₂ saturation of < 97.3% and the percentage of total sleep time with O₂ saturation < 90% higher than 2.7% were associated with ACS. There was no difference in nocturnal hypoxemia between patients with single and multiple ACS admissions.

CONCLUSIONS

Nocturnal hypoxemia later in life is associated with previous ACS admissions in children with SCD. This can increase the yield of interpreting polysomnograms in this vulnerable population. Prospective studies are needed to determine the temporal relations of nocturnal hypoxemia and ACS, which may identify a modifiable risk for ACS.

Chronic organ injuries in children with sickle cell disease

Median life expectancy of patients with sickle cell disease has increased to up to 55 years but there are still frequent cases of premature death, mostly in patients with pre-existing organ failure such as pulmonary hypertension, kidney injury, and cerebral vasculopathy. Most organ injuries remain asymptomatic for a long time and can only be detected through early systematic screening. Protocols combining assessment of velocities on transcranial Doppler and regular transfusions in patients with abnormal velocities have been demonstrated to dramatically reduce the risk of stroke. In contrast, no consensus has been reached on systematic screening or therapy for silent cerebral infarcts. The prognostic significance of increased tricuspid regurgitant jet velocity on echocardiography has not yet been identified in children, whereas increased albuminuria is a good predictor of kidney injury. Finally, screening for hip and eye disorder is recommended; however, different countries adopt different screening strategies. Hydroxyurea is probably of potential benefit in preventing chronic organ damage but this requires further study in order to be fully demonstrated. Efficacy and safety of the other new drugs available are also under investigation.

The burden of obstructive sleep apnea in pediatric sickle cell disease: a Kids' inpatient database study

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is associated with cardiovascular and cerebrovascular morbidity. Patients with sickle cell disease (SCD) are at increased risk for both neurologic complications (NC) and OSA. However, the relationship between OSA and SCD complications is unclear. We hypothesized that there would be an association between OSA diagnosis and SCD complications.

METHODS

Hospital discharge records of patients with SCD aged < 19 years were obtained for the years 1997, 2000, 2003, 2006, 2009, and 2012 from the Kid's Inpatient Database. The primary outcome, NC, a composite of stroke, transient ischemic attack, and seizures. Secondary outcomes included acute chest syndrome (ACS), vaso-occlusive crisis, length of hospital stay, and inflation-adjusted cost of hospitalization. Multivariable regression was conducted to ascertain the association of OSA with primary and secondary outcomes. Analyses were adjusted for the use of noninvasive mechanical ventilation (NIMV) to determine its role as NC risk modifier.

RESULTS

There were 203,705 SCD discharges included in the analysis, of which 2,820 (1.4%) and 4,447 (2.2%) also included OSA and NC diagnoses. Multivariable logistic regression indicated that OSA was associated with NC (adjusted odds ratio [OR], 1.50 [95% CI 1.02-2.21], p = 0.039) and ACS (OR, 1.34 [95% CI 1.08-1.67], p = 0.009) in children with SCD. In the multivariable analysis adjusted for NIMV, the significant association between OSA and NC was no longer observed (OR, 1.39 [95% CI 0.94-2.05], p = 0.100).

CONCLUSIONS

OSA is associated with a 50% increase of odds of NC in children with SCD in this nationwide dataset. The use of NIMV to treat OSA may modify the risk of OSA-associated NC.

Long-term oxygen therapy in children with sickle cell disease and hypoxaemia

OBJECTIVE

To evaluate the acceptability and safety profile of nocturnal long-term oxygen therapy (LTOT) in children with sickle cell disease (SCD) and chronic hypoxaemia.

DESIGN

Retrospective cohort study.

PATIENTS, SETTING AND INTERVENTION

Children with SCD who started LTOT from 2014 to early 2019 in two tertiary hospitals in London, UK were retrospectively enrolled. Patients who started disease-modifying therapies <12 months before LTOT or while on LTOT were excluded.

MAIN OUTCOME MEASURES

Minor and major adverse events during LTOT were reported. Laboratory and clinical data, transcranial Doppler (TCD) scans and overnight oximetry studies performed at steady state within 12 months before and after starting LTOT were compared.

RESULTS

Nineteen children (10 males; median age 12 years, range 6-15) were included. Nearly half of them (9/19; 47%) were on hydroxyurea at baseline. No child discontinued LTOT because of intolerance or poor adherence. No major adverse events were reported. Laboratory data did not show significant changes in haemoglobin and reticulocyte count after 1 year of follow-up. No statistically significant change in the incidence of vaso-occlusive pain events was noted (median annual rate from 0.5 to 0 episode per patient/year; p=0.062). Overnight oximetry tests performed while on LTOT showed improvements in all oxygen saturation parameters (mean overnight and nadir SpO₂, % of time spent with SpO₂ <90%) compared with the baseline.

CONCLUSION

LTOT is a safe and feasible treatment option for children with SCD and chronic hypoxaemia.

Beneficial effects of adenotonsillectomy in children with sickle cell disease

Tonsillectomy and adenoidectomy (T&A) is frequently performed in children with sickle cell disease (SCD). Our aim was to evaluate the impact of this surgery on overnight oxygenation and rates of complications in these patients.

Children with SCD who underwent T&A between 2008 and 2014 in two tertiary hospitals were retrospectively evaluated. Overnight oximetry and admission rates due to vaso-occlusive pain episodes (VOEs) and acute chest syndrome (ACS) in the year preceding and following the surgery were compared.

19 patients (10 males, 53%) with a median age of 6 years (range 3.5–8) were included. A significant increase of mean overnight arterial oxygen saturation measured by pulse oximetry (S_pO2) (from 93±3.6% to 95.3±2.8%, p=0.001), nadir S_pO2 (from 83.0±7.1% to 88±4.1%, p=0.004) and a reduction of 3% oxygen desaturation index (from a median value of 5.7 to 1.8, p=0.003) were shown. The mean annual rate of ACS decreased from 0.6±1.22 to 0.1±0.2 events per patient-year (p=0.003), while the mean cumulative rate of hospitalisations for all causes and the incidence of VOEs were not affected.

T&A improved nocturnal oxygenation and was also associated with a reduction in the incidence of ACS at 1-year follow-up after surgery.

In children with SCD, this retrospective analysis suggests that tonsillectomy and adenoidectomy may have a beneficial effect on nocturnal oxygenation level and the rate of ACS. This finding will need further confirmation in prospective and larger studies.https://bit.ly/3gL6gaU

Management of chronic respiratory complications in children and adolescents with sickle cell disease

Sickle cell disease (SCD) is a life-threatening hereditary blood disorder that affects millions of people worldwide, especially in sub-Saharan Africa. This condition has a multi-organ involvement and highly vascularised organs, such as the lungs, are particularly affected. Chronic respiratory complications of SCD involve pulmonary vascular, parenchymal and airways alterations. A progressive decline of lung function often begins in childhood. Asthma, sleep-disordered breathing and chronic hypoxaemia are common and associated with increased morbidity. Pulmonary hypertension is a serious complication, more common in adults than in children. Although there is a growing attention towards respiratory care of patients with SCD, evidence regarding the prognostic meaning and optimal management of pulmonary issues in children with this condition is limited.This narrative review presents state-of-the-art evidence regarding the epidemiology, pathophysiology and therapeutic options for chronic respiratory complications commonly seen in paediatric patients with SCD. Furthermore, it highlights the gaps in the current knowledge and indicates future directions for studies that aim to improve our understanding of chronic respiratory complications in children with SCD.

Higher oxygen saturation with hydroxyurea in paediatric sickle cell disease

INTRODUCTION

Sickle cell disease (SCD) is one of the most common inherited diseases worldwide. It is associated with lifelong morbidity and reduced life expectancy. Hydroxyurea (HU) has been shown to reduce the frequency and severity of vaso-occlusive episodes in SCD. Hypoxaemia and intermittent nocturnal oxygen desaturations occur frequently in children with SCD and contribute to the associated morbidity, including risk of cerebrovascular disease.

OBJECTIVE

To evaluate the effect of HU on oxygen saturation (SpO₂) overnight and on daytime SpO₂ spot checks in children with SCD.

METHODS

A retrospective review of children with SCD and respiratory problems who attended two UK tertiary sickle respiratory clinics and were treated with HU. Longitudinal data were collected from 2 years prior and up to 3 years after the commencement of HU.

RESULTS

Forty-three children, 23 males (53%) with a median age of 9 (range 1.8-18) years were included. In the 21 children who had comparable sleep studies before and after starting HU, mean SpO₂ was higher (95.2% from 93.5%, p=0.01) and nadir SpO₂ was higher (87.2% from 84.3%, p=0.009) when taking HU. In 32 of the children, spot daytime oxygen saturations were also higher (96.3% from 93.5%, p=0.001).

CONCLUSION

Children with SCD had higher oxygen saturation overnight and on daytime spot checks after starting HU. These data suggest HU may be helpful for treating persistent hypoxaemia in children with SCD pending more evidence from a randomised clinical trial.

Cerebral oxygen metabolism in adults with sickle cell disease

In sickle cell disease (SCD), oxygen delivery is impaired due to anemia, especially during times of increased metabolic demand, and cerebral blood flow (CBF) must increase to meet changing physiologic needs. But hyperemia limits cerebrovascular reserve (CVR) and ischemic risk prevails despite elevated CBF. The cerebral metabolic rate of oxygen (CMRO₂ ) directly reflects oxygen supply and consumption and may therefore be more insightful than flow-based CVR measures for ischemic risk in SCD. We hypothesized that adults with SCD have impaired CMRO₂ at rest and that a vasodilatory challenge with acetazolamide would improve CMRO₂ . CMRO₂ was calculated from CBF and oxygen extraction fraction (OEF), measured with arterial spin labeling and T₂ -prepared tissue relaxation with inversion recovery (T₂ -TRIR) MRI. We studied 36 adults with SCD without a clinical history of overt stroke, and nine healthy controls. As expected, CBF was higher in patients with SCD versus controls (mean ± SD: 74 ± 16 versus 46 ± 5 mL/100 g/min, P < .001), resulting in similar oxygen delivery (SCD: 377 ± 67 versus controls: 368 ± 42 μmol O₂ /100g/min, P = .69). OEF was lower in patients versus controls (27 ± 4 versus 35 ± 4%, P < .001), resulting in lower CMRO₂ in patients versus controls (102 ± 24 versus 127 ± 20 μmol O₂ /100g/min, P = .002). After acetazolamide, CMRO₂ declined further in patients (P < .01) and did not decline significantly in controls (P = .78), indicating that forcing higher CBF worsened oxygen utilization in SCD patients. This lower CMRO₂ could reflect variation between healthy and unhealthy vascular beds in terms of dilatory capacity and resistance whereby dysfunctional vessels become more oxygen-deprived, hence increasing the risk of localized ischemia.

The effect of obstructive sleep apnea syndrome on serum S100B and NSE levels: a systematic review and meta-analysis of observational studies

Background

Obstructive sleep apnea syndrome (OSAS) is a common disorder that is accompanied by structural brain changes. This meta-analysis aimed to evaluate the effect of OSAS on the serum levels of astrocytic protein (S100B) and neuron-specific enolase (NSE) in observational studies.

Methods

A comprehensive search was performed in the PubMed/Medline, Web of Science, Scopus, ScienceDirect, and Cochrane Library databases to assess the serum level of S100B and/or NSE in patients with OSAS and/or controls. The quality of the study was evaluated by the Newcastle-Ottawa Scale (NOS). A random-effects model was performed using RevMan 5.3 with the mean difference (MD) and 95% confidence intervals (CIs).

Results

Out of 63 studies found in the mentioned databases and one identified by a manual search, nine studies were included and analyzed in this meta-analysis (three cross-sectional and six case-control studies). The analysis showed that the S100B [MD = 53.58 pg/ml, 95%CI: 1.81, 105.35; P = 0.04] and NSE levels [MD = 3.78 ng/ml, 95%CI: 2.07, 5.48; P < 0.0001] were significantly higher in patients than the controls. However, there were no significant differences between the S100B [MD = -28.00 pg/ml, 95%CI: − 79.48, 23.47; P = 0.29] and NSE levels [MD = 0.49 ng/ml, 95%CI: − 0.82, 1.80; P = 0.46].

Conclusions

This meta-analysis found elevated serum S100B and NSE levels in OSAS patients compared to the controls, which suggests that these markers may be used as peripheral indicators of brain damage in OSAS.

Comparison of pulse oximetry and earlobe blood gas with CO-oximetry in children with sickle cell disease: a retrospective review

OBJECTIVES

To investigate the agreement between pulse oximetry (SpO₂) and oxygen saturation (SaO₂) measured by CO-oximetry on arterialised earlobe blood gas (EBG) in children and adolescents with sickle cell disease (SCD).

DESIGN AND SETTING

We retrospectively reviewed 39 simultaneous and paired SaO₂ EBG and SpO₂ measurements from 33 ambulatory patients with SCD (32 subjects with Haemoglobin SS and one with Haemoglobin Sß⁺, 52% male, mean±SD age 11.0±3.6, age range 5-18). Measurements were performed between 2012 and 2015 when participants were asymptomatic. Hypoxaemia was defined as SaO₂ ≤93%. A Bland-Altman analysis was performed to assess the accuracy of SpO₂ as compared with EBG SaO₂.

RESULTS

The mean±SD SpO₂ and SaO₂ values in the same patients were, respectively, 93.6%±3.7% and 94.3%±2.9%. The bias SpO₂-SaO₂ was -0.7% (95% limits of agreement from -5.4% to 4.1%) and precision was 2.5%. In 9/39 (23%) cases, the difference in SpO₂-SaO₂ was greater than the expected error range ±2%, with SaO₂ more often underestimated by SpO₂ (6/9), especially at SpO₂values ≤93%. Thirteen participants (33%) were hypoxaemic. The sensitivity of SpO₂ for hypoxaemia was 100%, specificity 85% and positive predictive value 76%.

CONCLUSIONS

Pulse oximetry was inaccurate in almost a quarter of measurements in ambulatory paediatric patients with SCD, especially at SpO₂values ≤93%. In these cases, oxygen saturation can be confirmed through EBG CO-oximetry, which is easier to perform and less painful than traditional arterial blood sampling.

Sleep-disordered breathing and comorbidities: role of the upper airway and craniofacial skeleton

Obstructive sleep-disordered breathing (SDB), which includes primary snoring through to obstructive sleep apnea syndrome (OSAS), may cause compromise of respiratory gas exchange during sleep, related to transient upper airway narrowing disrupting ventilation, and causing oxyhemoglobin desaturation and poor sleep quality. SDB is common in chronic disorders and has significant implications for health. With prevalence rates globally increasing, this condition is causing a substantial burden on health care costs. Certain populations, including people with sickle cell disease (SCD), exhibit a greater prevalence of OSAS. A review of the literature provides the available normal polysomnography and oximetry data for reference and documents the structural upper airway differences between those with and without OSAS, as well as between ethnicities and disease states. There may be differences in craniofacial development due to atypical growth trajectories or extramedullary hematopoiesis in anemias such as SCD. Studies involving MRI of the upper airway illustrated that OSAS populations tend to have a greater amount of lymphoid tissue, smaller airways, and smaller lower facial skeletons from measurements of the mandible and linear mental spine to clivus. Understanding the potential relationship between these anatomical landmarks and OSAS could help to stratify treatments, guiding choice towards those which most effectively resolve the obstruction. OSAS is relatively common in SCD populations, with hypoxia as a key manifestation, and sequelae including increased risk of stroke. Combatting any structural defects with appropriate interventions could reduce hypoxic exposure and consequently reduce the risk of comorbidities in those with SDB, warranting early treatment interventions.

American Society of Hematology 2019 guidelines for sickle cell disease: cardiopulmonary and kidney disease

BACKGROUND

Prevention and management of end-organ disease represent major challenges facing providers of children and adults with sickle cell disease (SCD). Uncertainty and variability in the screening, diagnosis, and management of cardiopulmonary and renal complications in SCD lead to varying outcomes for affected individuals.

OBJECTIVE

These evidence-based guidelines of the American Society of Hematology (ASH) are intended to support patients, clinicians, and other health care professionals in their decisions about screening, diagnosis, and management of cardiopulmonary and renal complications of SCD.

METHODS

ASH formed a multidisciplinary guideline panel that included 2 patient representatives and was balanced to minimize potential bias from conflicts of interest. The Mayo Evidence-Based Practice Research Program supported the guideline development process, including performing systematic evidence reviews up to September 2017. The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The panel used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach, including GRADE evidence-to-decision frameworks, to assess evidence and make recommendations, which were subject to public comment.

RESULTS

The panel agreed on 10 recommendations for screening, diagnosis, and management of cardiopulmonary and renal complications of SCD. Recommendations related to anticoagulation duration for adults with SCD and venous thromboembolism were also developed.

CONCLUSIONS

Most recommendations were conditional due to a paucity of direct, high-quality evidence for outcomes of interest. Future research was identified, including the need for prospective studies to better understand the natural history of cardiopulmonary and renal disease, their relationship to patient-important outcomes, and optimal management.

Home Oxygen Therapy for Children. An Official American Thoracic Society Clinical Practice Guideline

Background: Home oxygen therapy is often required in children with chronic respiratory conditions. This document provides an evidence-based clinical practice guideline on the implementation, monitoring, and discontinuation of home oxygen therapy for the pediatric population.

Methods: A multidisciplinary panel identified pertinent questions regarding home oxygen therapy in children, conducted systematic reviews of the relevant literature, and applied the Grading of Recommendations, Assessment, Development, and Evaluation approach to rate the quality of evidence and strength of clinical recommendations.

Results: After considering the panel’s confidence in the estimated effects, the balance of desirable (benefits) and undesirable (harms and burdens) consequences of treatment, patient values and preferences, cost, and feasibility, recommendations were developed for or against home oxygen therapy specific to pediatric lung and pulmonary vascular diseases.

Conclusions: Although home oxygen therapy is commonly required in the care of children, there is a striking lack of empirical evidence regarding implementation, monitoring, and discontinuation of supplemental oxygen therapy. The panel formulated and provided the rationale for clinical recommendations for home oxygen therapy based on scant empirical evidence, expert opinion, and clinical experience to aid clinicians in the management of these complex pediatric patients and identified important areas for future research.

Vaso-Occlusion in Sickle Cell Disease: Is Autonomic Dysregulation of the Microvasculature the Trigger?

Sickle cell disease (SCD) is an inherited hemoglobinopathy characterized by polymerization of hemoglobin S upon deoxygenation that results in the formation of rigid sickled-shaped red blood cells that can occlude the microvasculature, which leads to sudden onsets of pain. The severity of vaso-occlusive crises (VOC) is quite variable among patients, which is not fully explained by their genetic and biological profiles. The mechanism that initiates the transition from steady state to VOC remains unknown, as is the role of clinically reported triggers such as stress, cold and pain. The rate of hemoglobin S polymerization after deoxygenation is an important determinant of vaso-occlusion. Similarly, the microvascular blood flow rate plays a critical role as fast-moving red blood cells are better able to escape the microvasculature before polymerization of deoxy-hemoglobin S causes the red cells to become rigid and lodge in small vessels. The role of the autonomic nervous system (ANS) activity in VOC initiation and propagation has been underestimated considering that the ANS is the major regulator of microvascular blood flow and that most triggers of VOC can alter the autonomic balance. Here, we will briefly review the evidence supporting the presence of ANS dysfunction in SCD, its implications in the onset of VOC, and how differences in autonomic vasoreactivity might potentially contribute to variability in VOC severity.

Does Obstructive Sleep Apnea Increase Cognitive Deficits in Pediatric Sickle Cell Disease?

OBJECTIVES

Although pediatric obstructive sleep apnea (OSA) is estimated to affect 2-3% of the general population, its prevalence in sickle cell disease (SCD) is much higher, with research suggesting a prevalence rate of upwards of 40%. Despite the similar underlying pathophysiological mechanisms of neurocognitive effects in pediatric OSA and SCD, there is a scarcity of information on how these two conditions interact. The aim of this study was to better understand the contribution of sleep apnea to neurocognitive deficits in children diagnosed with SCD.

METHOD

This study assessed cognitive function in 26 children with comorbid SCD and OSA, 39 matched comparisons with SCD only, and 59 matched comparisons in children without a chronic health condition.

RESULTS

There were significant differences on measures of processing speed and reading decoding, with children without a chronic health condition scoring better than both chronic health condition groups. Additionally, the no chronic health condition group performed better on a test of quantitative knowledge and reasoning and a test of visual-spatial construction than the SCD-only group. Contrary to our hypotheses, there were no between-group differences suggesting an additive impact of OSA on cognition. Exploratory analyses revealed associations within the group that had OSA showing that more severe OSA correlated with lower performance on measures of processing speed and quantitative knowledge/reasoning.

CONCLUSIONS

Children with comorbid OSA and SCD do not present with greater deficits in cognitive functioning than children with SCD alone. However, severe OSA may confer additional risk for neurocognitive impairments.

Identifying Clinical and Research Priorities in Sickle Cell Lung Disease. An Official American Thoracic Society Workshop Report

Background: Pulmonary complications of sickle cell disease (SCD) are diverse and encompass acute and chronic disease. The understanding of the natural history of pulmonary complications of SCD is limited, no specific therapies exist, and these complications are a primary cause of morbidity and mortality.Methods: We gathered a multidisciplinary group of pediatric and adult hematologists, pulmonologists, and emergency medicine physicians with expertise in SCD-related lung disease along with an SCD patient advocate for an American Thoracic Society-sponsored workshop to review the literature and identify key unanswered clinical and research questions. Participants were divided into four subcommittees on the basis of expertise: 1) acute chest syndrome, 2) lower airways disease and pulmonary function, 3) sleep-disordered breathing and hypoxia, and 4) pulmonary vascular complications of SCD. Before the workshop, a comprehensive literature review of each subtopic was conducted. Clinically important questions were developed after literature review and were finalized by group discussion and consensus.Results: Current knowledge is based on small, predominantly observational studies, few multicenter longitudinal studies, and even fewer high-quality interventional trials specifically targeting the pulmonary complications of SCD. Each subcommittee identified the three or four most important unanswered questions in their topic area for researchers to direct the next steps of clinical investigation.Conclusions: Important and clinically relevant questions regarding sickle cell lung disease remain unanswered. High-quality, multicenter, longitudinal studies and randomized clinical trials designed and implemented by teams of multidisciplinary clinician-investigators are needed to improve the care of individuals with SCD.

The Role of Family Functioning in the Development of Executive Functions in Preschool Children with Sickle Cell Anemia

Executive functions are compromised in children with sickle cell anemia. There is limited research on the development of executive functions in preschool children with sickle cell anemia and the factors that contribute to executive dysfunction. We looked at the relation between biomedical and environmental factors, including family functioning and socioeconomic status, and executive functions in 22 preschool children with sickle cell anemia. We found that family functioning was the strongest predictor of executive outcomes in young children with sickle cell anemia with no evidence for an influence of disease severity at this early stage.

Vascular Instability and Neurological Morbidity in Sickle Cell Disease: An Integrative Framework

It is well-established that patients with sickle cell disease (SCD) are at substantial risk of neurological complications, including overt and silent stroke, microstructural injury, and cognitive difficulties. Yet the underlying mechanisms remain poorly understood, partly because findings have largely been considered in isolation. Here, we review mechanistic pathways for which there is accumulating evidence and propose an integrative systems-biology framework for understanding neurological risk. Drawing upon work from other vascular beds in SCD, as well as the wider stroke literature, we propose that macro-circulatory hyper-perfusion, regions of relative micro-circulatory hypo-perfusion, and an exhaustion of cerebral reserve mechanisms, together lead to a state of cerebral vascular instability. We suggest that in this state, tissue oxygen supply is fragile and easily perturbed by changes in clinical condition, with the potential for stroke and/or microstructural injury if metabolic demand exceeds tissue oxygenation. This framework brings together recent developments in the field, highlights outstanding questions, and offers a first step toward a linking pathophysiological explanation of neurological risk that may help inform future screening and treatment strategies.

Association Between Periodic Limb Movements in Sleep and Cerebrovascular Changes in Children With Sickle Cell Disease

STUDY OBJECTIVES

Periodic limb movements (PLMs) have been associated with increased risk of stroke, but there is currently scarce research exploring this relationship in the setting of sickle cell disease (SCD). The aim of this study was to explore whether increased PLMs in children with SCD are associated with increased risk of cerebrovascular disease and to determine if there are any clinical or laboratory differences between children with SCD with elevated periodic limb movement index (PLMI) versus those with normal PLMI.

METHODS

This study is a comprehensive review of medical records of 129 children with SCD (aged ≤ 18 years) who had undergone polysomnography for evaluation of sleep-disordered breathing.

RESULTS

Elevated PLMI (PLMI > 5 events/h) was present in 42% (54/129) of children with SCD. Children with elevated PLMI were found to have higher percentage of hemoglobin S, lower total iron, higher arousal index and tendency toward elevated transcranial Doppler velocity (P = .063, odds ratio = 3.9, 95% CI 0.93-16.22). While association between elevated PLMI and isolated cerebrovascular stenosis (P = .050, odds ratio 5.6, 95% CI 1.0-31.10) trended toward significance, there was significantly greater proportion of children with elevated PLMI who had cerebrovascular stenosis with Moyamoya disease (P = .046) as demonstrated by magnetic resonance imaging (MRI).

CONCLUSIONS

The prevalence of elevated PLMI in children with SCD was higher than in previously published data. Elevated PLMI was significantly associated with greater rates of cerebrovascular disease as detected by MRI.

Neurologic complications in children under five years with sickle cell disease

INTRODUCTION

Sickle Cell Disease (SCD) is one of the most common genetic diseases in the world affecting every organ. The major challenge in the medical care of children with SCD is preventing end-organ dysfunction, particularly the brain. Major neurologic complications in children less than five years with SCD include, but are not limited to, Silent cerebral infarct, cerebral sinus thrombosis, epilepsy, reversible encephalopathy syndrome, and ischemic and hemorrhagic stroke. Recurrent headaches and migraine are not rare in children under five years with SCD. This review will focus on the neurologic complications and the description of the modifiable risk factors in children less than 5 years of age with emphasis on differences between high and low resource settings.

AREAS COVERED

Neurologic complications of children under 5 years of age and the modifiable risk factors. The PUBMED database was searched using medical subject headings (MeSH) and keywords for articles regarding neurologic complications in children under 5 years of age.

CONCLUSION

Neurologic complications in children under five years of age with SCD may be more frequent than currently reported, among which Silent cerebral infarct and cognitive impairment are the most common.

Investigating the Sleep-Pain Relationship in Youth with Sickle Cell Utilizing mHealth Technology

OBJECTIVES

The current study utilized mHealth technologies that were objective (e.g., sleep actigraphy and pulse oximetry) and time-sensitive (e.g., ecological momentary assessments [EMAs]) to characterize sleep in youth with sickle cell disease (SCD) and investigate the relationships between sleep variables and pain. It also investigated the influence of age on sleep and the sleep-pain relationship.

METHODS

Eighty-eight youth with SCD (aged 8-17 years) were recruited from three regional pediatric SCD clinics. Youth completed twice daily EMAs for up to 4 weeks to assess nighttime subjective sleep quality and daily pain. They also wore a sleep actigraph for 2 weeks to assess sleep duration, sleep efficiency, and sleep latency, and a wrist-worn pulse oximeter for two nights to assess whether they had sleep apnea. Multilevel models were calculated predicting daily SCD pain using the sleep variables, age, and the interaction between age and the sleep variables.

RESULTS

None of the sleep variables were related to one another. Poor subjective sleep quality during the night was related to high pain severity the next day, and high pain was related to poor subjective sleep quality that night. Older age was associated with poorer subjective sleep quality, shorter duration of nighttime sleep, and high sleep latency. Also, findings indicated that as age increased, the strength of the relationship between poor continuous subjective sleep quality and high pain severity increased.

CONCLUSIONS

Future research is needed to examine possible mechanisms connecting subjective sleep quality to high pain.

Hemodynamic provocation with acetazolamide shows impaired cerebrovascular reserve in adults with sickle cell disease

Sickle cell disease is characterized by chronic hemolytic anemia and vascular inflammation, which can diminish the vasodilatory capacity of the small resistance arteries, making them less adept at regulating cerebral blood flow. Autoregulation maintains adequate oxygen delivery, but when vasodilation is maximized, the low arterial oxygen content can lead to ischemia and silent cerebral infarcts. We used magnetic resonance imaging of cerebral blood flow to quantify whole-brain cerebrovascular reserve in 36 adult patients with sickle cell disease (mean age, 31.9±11.3 years) and 11 healthy controls (mean age, 37.4±15.4 years), and we used high-resolution 3D FLAIR magnetic resonance imaging to determine the prevalence of silent cerebral infarcts. Cerebrovascular reserve was calculated as the percentage change in cerebral blood flow after a hemodynamic challenge with acetazolamide. Co-registered lesion maps were used to demonstrate prevalent locations for silent cerebral infarcts. Cerebral blood flow was elevated in patients with sickle cell disease compared to controls (median [interquartile range]: 82.8 [20.1] vs 51.3 [4.8] mL/100g/min, P<0.001). Cerebral blood flow was inversely associated with age, hemoglobin, and fetal hemoglobin, and correlated positively with bilirubin, and LDH, indicating that cerebral blood flow may reflect surrogates of hemolytic rate. Cerebrovascular reserve in sickle cell disease was decreased by half compared to controls (34.1 [33.4] vs 69.5 [32.4] %, P<0.001) and was associated with hemoglobin and erythrocyte count indicating anemia-induced hemodynamic adaptations. In total, 29/36 patients (81%) and 5/11 controls (45%) had silent cerebral infarcts (median volume of 0.34 vs 0.02 mL, P=0.03). Lesions were preferentially located in the borderzone. In conclusion, patients with sickle cell disease have a globally reduced cerebrovascular reserve as determined by arterial spin labeling with acetazolamide and reflects anemia-induced impaired vascular function in sickle cell disease. This study was registered at clinicaltrials.gov identifier 02824406.

A ten year review of the sickle cell program in Muhimbili National Hospital, Tanzania

Background

Africa has the highest burden of Sickle cell disease (SCD) but there are few large, systematic studies providing reliable descriptions of the disease spectrum. Tanzania, with 11,000 SCD births annually, established the Muhimbili Sickle Cell program aiming to improve understanding of SCD in Africa. We report the profile of SCD seen in the first 10 years at Muhimbili National Hospital (MNH).

Methods

Individuals seen at MNH known or suspected to have SCD were enrolled at clinic and laboratory testing for SCD, haematological and biochemical analyses done. Ethnicity was self-reported. Clinical and laboratory features of SCD were documented. Comparison was made with non-SCD population as well as within 3 different age groups (< 5, 5–17 and ≥ 18 years) within the SCD population.

Results

From 2004 to 2013, 6397 individuals, 3751 (58.6%) SCD patients, were enrolled, the majority (47.4%) in age group 5–17 years. There was variation in the geographical distribution of SCD. Individuals with SCD compared to non-SCD, had significantly lower blood pressure and peripheral oxygen saturation (SpO₂). SCD patients had higher prevalence of severe anemia, jaundice and desaturation (SpO₂ < 95%) as well as higher levels of reticulocytes, white blood cells, platelets and fetal hemoglobin. The main causes of hospitalization for SCD within a 12-month period preceding enrolment were pain (adults), and fever and severe anemia (children). When clinical and laboratory features were compared in SCD within 3 age groups, there was a progressive decrease in the prevalence of splenic enlargement and an increase in prevalence of jaundice. Furthermore, there were significant differences with monotonic trends across age groups in SpO2, hematological and biochemical parameters.

Conclusion

This report confirms that the wide spectrum of clinical expression of SCD observed elsewhere is also present in Tanzania, with non-uniform geographical distribution across the country. Age-specific analysis is consistent with different disease-patterns across the lifespan.

How I treat hypoxia in adults with hemoglobinopathies and hemolytic disorders

Hemoglobinopathies are caused by genetic mutations that result in abnormal hemoglobin molecules, resulting in hemolytic anemia. Chronic complications involving the lung parenchyma, vasculature, and cardiac function in hemoglobinopathies result in impaired gas exchange, resulting in tissue hypoxia. Hypoxia is defined as the deficiency in the amount of oxygen reaching the tissues of the body and is prevalent in patients with hemoglobinopathies, and its cause is often multifactorial. Chronic hypoxia in hemoglobinopathies is often a sign of disease severity and is associated with increased morbidity and mortality. Therefore, a thorough understanding of the pathophysiology of hypoxia in these disease processes is important in order to appropriately treat the underlying cause and prevent complications. In this article, we discuss management of hypoxia based on three different cases: sickle cell disease, β-thalassemia, and hereditary spherocytosis. These cases are used to review the current understanding of the disease pathophysiology, demonstrate the importance of a thorough clinical history and physical examination, explore diagnostic pathways, and review the current management.

Adenotonsillectomy in children with sickle cell disease and obstructive sleep apnea

INTRODUCTION

Obstructive sleep apnea (OSA) is prevalent and may be more severe in children with Sickle Cell Disease (SCD) compared to the general pediatric population.

OBJECTIVES

The objective of this study was to describe the therapeutic effects and complications of tonsillectomy and adenoidectomy (T&A) for treatment of OSA in children with SCD.

METHODS

A comprehensive database of pediatric SCD patients was reviewed to identify all patients who underwent T&A between 2010 and 2016. An IRB-approved, retrospective review of laboratory values, perioperative course, pre- and post-T&A hospital utilization, and polysomnography was conducted.

RESULTS

There were 132 SCD children (108 HbSS) who underwent T&A. Mean age was 7.6 ± 4.6 years. The mean baseline hemoglobin of these patients was 9.3 ± 1.4 g/dL; 72.7% of patients had pre-operative transfusion, such that the mean Hb at time of T&A was 11.4 ± 1.0 g/dL. The average admission length surrounding T&A was 3.5 ± 1.2 days. Complications were documented in 11.4% of operative cases. Polysomnography was available in 104 pre-T&A and 45 post-T&A. The Apnea-Hypopnea Index decreased on post-T&A polysomnogram (7.6 ± 8.7 vs. 1.3 ± 1.9, p = 0.0001). The O2 nadir improved on post-T&A polysomnogram (81.2 ± 10.8 vs. 89.3 ± 7, p = 0.0003). Emergency room visits (mean events per year) decreased post-operatively (2.6 ± 2.8 vs. 1.8 ± 2.2, p = 0.0002).

CONCLUSIONS

T&A can be a safe and effective option to treat OSA in pediatric patients with SCD and was significantly associated with reduced AHI and fewer ER visits post-operatively.

Cerebral perfusion characteristics show differences in younger versus older children with sickle cell anaemia: Results from a multiple-inflow-time arterial spin labelling study

Sickle cell anaemia (SCA) is associated with chronic anaemia and oxygen desaturation, which elevate cerebral blood flow (CBF) and increase the risk of neurocognitive complications. Arterial spin labelling (ASL) provides a methodology for measuring CBF non-invasively; however, ASL techniques using only a single inflow time are not sufficient to fully characterize abnormal haemodynamic behaviour in SCA. This study investigated haemodynamic parameters from a multi-inflow-time ASL acquisition in younger (8-12 years) and older (13-18 years) children with SCA with and without silent cerebral infarction (SCI+/-) (n = 20 and 19 respectively, 6 and 4 SCI+ respectively) and healthy controls (n = 9 and 7 respectively). Compared with controls, CBF was elevated globally in both groups of patients. In the younger SCA patients, blood oxygen content was negatively correlated with CBF in the middle and posterior cerebral artery territories and significantly positively correlated with bolus arrival time (BAT) in the anterior and middle cerebral artery territories. In older children, SCA patients had significantly shorter BAT than healthy controls and there was a significant negative correlation between CBF and oxygen content only in the territory of the posterior cerebral artery, with a trend for a correlation in the anterior cerebral artery but no relationship for the middle cerebral artery territory. In the younger group, SCI+ patients had significantly higher CBF in the posterior cerebral artery territory (SCI+ mean = 92.78 ml/100 g/min; SCI- mean = 72.71 ml/100 g/min; F = 4.28, p = 0.04), but this no longer reached significance when two children with abnormal transcranial Doppler and one with haemoglobin SC disease were excluded, and there were no significant differences between patients with and without SCI in the older children. With age, there appears to be increasing disparity between patients and controls in terms of the relationship between CBF and oxygen content in the anterior circulation, potentially predicting the risk of acute and chronic compromise of brain tissue.

White matter integrity and processing speed in sickle cell anemia

Objective

The purpose of this retrospective cross-sectional study was to investigate whether changes in white matter integrity are related to slower processing speed in sickle cell anemia.

Methods

Thirty-seven patients with silent cerebral infarction, 46 patients with normal MRI, and 32 sibling controls (age range 8–37 years) underwent cognitive assessment using the Wechsler scales and 3-tesla MRI. Tract-based spatial statistics analyses of diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) parameters were performed.

Results

Processing speed index (PSI) was lower in patients than controls by 9.34 points (95% confidence interval: 4.635–14.855, p = 0.0003). Full Scale IQ was lower by 4.14 scaled points (95% confidence interval: −1.066 to 9.551, p = 0.1), but this difference was abolished when PSI was included as a covariate (p = 0.18). There were no differences in cognition between patients with and without silent cerebral infarction, and both groups had lower PSI than controls (both p < 0.001). In patients, arterial oxygen content, socioeconomic status, age, and male sex were identified as predictors of PSI, and correlations were found between PSI and DTI scalars (fractional anisotropy r = 0.614, p < 0.00001; r = −0.457, p < 0.00001; mean diffusivity r = −0.341, p = 0.0016; radial diffusivity r = −0.457, p < 0.00001) and NODDI parameters (intracellular volume fraction r = 0.364, p = 0.0007) in widespread regions.

Conclusion

Our results extend previous reports of impairment that is independent of presence of infarction and may worsen with age. We identify processing speed as a vulnerable domain, with deficits potentially mediating difficulties across other domains, and provide evidence that reduced processing speed is related to the integrity of normal-appearing white matter using microstructure parameters from DTI and NODDI.

Genetic, laboratory and clinical risk factors in the development of overt ischemic stroke in children with sickle cell disease

Cerebrovascular disease, particularly stroke, is one of the most severe clinical complications associated with sickle cell disease and is a significant cause of morbidity in both children and adults. Over the past two decades, considerable advances have been made in the understanding of its natural history and enabled early identification and treatment of children at the highest risk. Transcranial Doppler screening and regular blood transfusions have markedly reduced the risk of stroke in children. However, transcranial Doppler has a limited positive predictive value and the pathophysiology of cerebrovascular disease is not completely understood. In this review, we will focus on the current state of knowledge about risk factors associated with ischemic stroke in patients with sickle cell disease. A search of PubMed was performed to identify studies. Full texts of the included articles were reviewed and data were summarized in a table. The coinheritance of alpha-thalassemia plays a protective role against ischemic stroke. The influence of other genetic risk factors is controversial, still preliminary, and requires confirmatory studies. Recent advances have established the reticulocyte count as the most important laboratory risk factor. Clinical features associated with acute hypoxemia as well as silent infarcts seem to influence the development of strokes in children. However, transcranial Doppler remains the only available clinical prognostic tool to have been validated. If our understanding of the many risk factors associated with stroke advances further, it may be possible to develop useful tools to detect patients at the highest risk early, improving the selection of children requiring intensification therapy.

Effects of hydroxyurea on blood rheology in sickle cell anemia: A two-years follow-up study

The aim of the present study was to test the effects of hydroxyurea (HU) therapy on clinical, hematological and hemorheological parameters in adult patients with sickle cell anemia (SCA). Hematological and hemorheological parameters were measured in 28 SCA patients before HU therapy (i.e., baseline) and at 6, 12 and 24 months of treatment. RBC deformability was determined by ektacytometry at 30 Pa. RBC aggregation properties were investigated by light-backscatter method. Blood viscosity was measured at 225 s-1 by a cone-plate viscometer. The rates of vaso-occlusive crises and acute chest syndrome were lower at 1 and 2 years of HU therapy compared to baseline. The proportion of patients with leg ulcers tended to decrease after 2 years of treatment. Hemoglobin oxygen saturation improved with HU therapy. HU therapy induced a decrease of platelet and white blood cell counts and a rise in fetal hemoglobin level and mean cell volume. While hemoglobin concentrations increased under HU, blood viscosity remained unchanged all along the study. RBC deformability increased over baseline values at 6 months of HU therapy and continued to rise until the end of the follow-up period. In conclusion, the improvement in RBC deformability probably compensates the increase of hemoglobin on blood viscosity and participates to the improvement of the clinical status of patients.

Haemoglobin oxygen saturation, leucocyte count and lactate dehydrogenase are predictors of elevated cerebral blood flow velocity in Nigerian children with sickle cell anaemia

BACKGROUND

Transcranial Doppler ultrasound (TCD) scan, which measures blood flow velocity through the time-averaged mean of maximum velocities (TAMMVs) in the internal carotid arteries and middle cerebral arteries, is a useful screening tool for predicting stroke risk in children with sickle cell anaemia (SCA).

AIM

To investigate which clinical and laboratory indices predict abnormal TCD velocity in children with SCA.

METHODS

Fifty-four SCA patients with normal TCD (TAMMV < 170 cm/s), classified as negative TCD (NTCD), and 93 patients with conditional and abnormal TCD velocities (TAMMV ≥ 170 cm/s) classified as positive TCD were recruited. The haemoglobin oxygen saturation, haematological variables, nitric oxide metabolites and lactate dehydrogenase activity of the patients were analysed.

RESULTS

The mean (SD) age was 7.16 (3.84) years (range 2-16). The median SpO₂ of the patients in the positive TCD group was significantly lower than that of the negative TCD group (p = 0.002). Multivariate logistic regression analysis indicated that the MCV [odds ratio (OR) 1.12, 95% confidence interval (CI) 1.04-1.22, p = 0.01)], MCH (OR 1.34, 95% CI 1.02-1.77, p = 0.04), leucocyte count (OR 1.26, 95% CI 1.07-1.49, p = 0.01) and lactate dehydrogenase (LDH) level (OR 1.00, 95% CI 1.00-1.01, p = 0.01) were independent predictors of high cerebral blood flow velocities.

CONCLUSIONS

These clinical and laboratory indices are characteristic of chronic hypoxia and severe anaemia and are predictors of abnormal cerebral blood flow velocity. They can be used to predict stroke risk in children with SCA when access to TCD screening is limited.

Overnight auto-adjusting continuous airway pressure + standard care compared with standard care alone in the prevention of morbidity in sickle cell disease phase II (POMS2b): study protocol for a randomised controlled trial

Background

In addition to pain, sickle cell anaemia (HbSS) complications include neurocognitive difficulties in attention and processing speed associated with low daytime and night-time oxygen saturation compounded by obstructive sleep apnoea (OSA). In the general population OSA is treated with continuous positive airways pressure (CPAP). The aim of this single-blind, randomised, controlled phase II trial is to compare auto-adjusting CPAP (APAP) with standard care to standard care alone in individuals with HbSS to determine whether the intervention improves attention and processing speed, brain structure, pain and quality of life.

Methods/Design

Eligibility criteria include: ability to provide informed consent; age > 8 years; diagnosis of HbSS; and mean overnight saturation of < 90% for < 30% of the night (i.e. not meeting current criteria for overnight oxygen therapy). Key exclusion criteria are: overnight respiratory support; respiratory or decompensated cardiac failure; chronic transfusion; or contraindications to APAP therapy or magnetic resonance imaging (MRI).

Sixty individuals with HbSS (30 children and 30 adults) will be randomised to standard care + APAP or standard care alone for six months. Minimisation factors are: age group (8–11, 12–15, 16–22 and > 23 years); silent infarction on MRI; minimum overnight oxygen saturation > 90% or < 90%; and hydroxyurea use.

For APAP individuals, the intervention is administered at home. Adherence and effectiveness are recorded using software documenting hours of use each night and overnight oximetry. Participant support in terms of appropriate facemask and facilitating adherence are provided by an unblinded sleep physiologist.

The primary outcome is change in the cancellation subtest from the Wechsler scales. Secondary outcomes include general cognitive functioning, quantitative brain MRI, blood and urine chemistry, quality of life and daily pain via a smartphone App (GoMedSolutions, Inc) and, where possible MRI heart, echocardiography, and 6-min walk. These outcomes will be assessed at baseline and after six months of treatment by assessors blind to treatment assignment.

Discussion

Altering oxygen saturation in HbSS may lead to bone marrow suppression. This risk will be reduced by monitoring full blood counts at baseline, two weeks, three months and six months, providing treatment as appropriate and reporting as safety events.

Trial registration

ISRCTN46012373. Registered on 10 July 2015.

Protocol Version: 6.0 Date: 24th December 2015

Sponsor: University Hospital Southampton. Sponsor’s protocol code: RHMCHIOT53

Nocturnal oxyhemoglobin desaturation and arteriopathy in a pediatric sickle cell disease cohort

OBJECTIVE

The purpose of this study of sickle cell disease (SCD) was to determine whether arteriopathy, measurable as intracranial vessel signal loss on magnetic resonance angiography (MRA), was associated with low nocturnal hemoglobin oxygen saturation (SpO2) or hemolytic rate, measurable as reticulocytosis or unconjugated hyperbilirubinemia.

METHODS

Ninety-five East London children with SCD without prior stroke had overnight pulse oximetry, of whom 47 (26 boys, 39 hemoglobin SS; mean age 9.1 ± 3.1 years) also had MRA, transcranial Doppler (TCD), steady-state hemoglobin, and reticulocytes within 34 months. Two radiologists blinded to the other data graded arteriopathy on MRA as 0 (none) or as increasing severity grades 1, 2, or 3.

RESULTS

Grades 2 or 3 arteriopathy (n = 24; 2 with abnormal TCD) predicted stroke/TIA compared with grades 0 and 1 (log-rank χ2 [1, n = 47] = 8.1, p = 0.004). Mean overnight SpO2 correlated negatively with reticulocyte percentage (r = -0.387; p = 0.007). Despite no significant differences across the degrees of arteriopathy in genotype, mean overnight SpO2 was higher (p < 0.01) in those with grade 0 (97.0% ± 1.6%) than those with grades 2 (93.9 ± 3.7%) or 3 (93.5% ± 3.0%) arteriopathy. Unconjugated bilirubin was not associated but reticulocyte percentage was lower (p < 0.001) in those with grade 0 than those with grades 2 and 3 arteriopathy. In multivariable logistic regression, lower mean overnight SpO2 (odds ratio 0.50, 95% confidence interval 0.26-0.96; p < 0.01) predicted arteriopathy independent of reticulocyte percentage (odds ratio 1.47, 95% confidence interval 1.15-1.87; p = 0.003).

CONCLUSION

Low nocturnal SpO2 and reticulocytosis are associated with intracranial arteriopathy in children with SCD. Preventative strategies might reduce stroke risk.

Sleep-disordered breathing in patients with sickle cell disease

Sickle cell disease is one of the most common hereditary hemoglobinopathies worldwide, and its vaso-occlusive and hemolytic crises cause considerable patient morbidity. A growing body of evidence has shown that sleep-disordered breathing, and in particular, obstructive sleep apnea, occurs at high frequency in the sickle cell population, and that there is significant overlap in the underlying pathophysiology of these two conditions. Through a variety of mechanisms including nocturnal hypoxemia and increased oxidative stress, production of pro-inflammatory cytokines, and endothelial dysfunction, sickle cell anemia and sleep-disordered breathing potentiate each other's clinical effects and end-organ complications. Here, we will review the shared pathophysiologic mechanisms of these conditions and discuss their clinical sequelae. We will also examine the results of studies that have been carried out with clinical intervention of nocturnal hypoxemia in patients with sickle cell disease in the attempts to overcome the complications of the disease. Finally, we will propose the areas of investigation that merit further investigations in future in patients with sickle cell disease and sleep-disordered breathing.

Graph Lasso-Based Test for Evaluating Functional Brain Connectivity in Sickle Cell Disease

Sickle cell disease (SCD) is a vascular disorder that is often associated with recurrent ischemia-reperfusion injury, anemia, vasculopathy, and strokes. These cerebral injuries are associated with neurological dysfunction, limiting the full developing potential of the patient. However, recent large studies of SCD have demonstrated that cognitive impairment occurs even in the absence of brain abnormalities on conventional magnetic resonance imaging (MRI). These observations support an emerging consensus that brain injury in SCD is diffuse and that conventional neuroimaging often underestimates the extent of injury. In this article, we postulated that alterations in the cerebral connectivity may constitute a sensitive biomarker of SCD severity. Using functional MRI, a connectivity study analyzing the SCD patients individually was performed. First, a robust learning scheme based on graphical lasso model and Fréchet mean was used for estimating a consistent descriptor of healthy brain connectivity. Then, we tested a statistical method that provides an individual index of similarity between this healthy connectivity model and each SCD patient's connectivity matrix. Our results demonstrated that the reference connectivity model was not appropriate to model connectivity for only 4 out of 27 patients. After controlling for the gender, two separate predictors of this individual similarity index were the anemia (p = 0.02) and white matter hyperintensities (WMH) (silent stroke) (p = 0.03), so that patients with low hemoglobin level or with WMH have the least similarity to the reference connectivity model. Further studies are required to determine whether the resting-state connectivity changes reflect pathological changes or compensatory responses to chronic anemia.