Autonomic reactivity and clinical severity in children with sickle cell disease

Cerebrovascular and cardiovascular autonomic regulation in sickle cell patients with white matter lesions

BACKGROUND AND PURPOSE

White matter lesions (WMLs) are frequent in sickle cell disease (SCD), with a prevalence described to be as high as 53% by age 30. Cerebrovascular regulation and cardiovascular autonomic regulation, more specifically the sympatho-vagal balance, can be altered in SCD. In this study the association between WMLs, cerebrovascular regulation and sympatho-vagal balance was assessed in SCD patients.

METHODS AND RESULTS

Sickle cell disease patients with no history of stroke were prospectively evaluated for cerebrovascular reactivity using the breath-holding test (BHT), the sympatho-vagal balance (ratio low frequency/high frequency [HF]) using heart rate variability parameters and cerebral autoregulation in the time domain using correlation index Mx, and arterial cerebral compliance based on continuous assessment of cerebral blood flow velocities using transcranial Doppler ultrasound and arterial blood pressure with photo-plethysmography. WMLs were assessed with magnetic resonance imaging using Fazekas score grading and the presence of lacunes. Forty-one patients (F/M 25/16) were included. Median age was 37.5 years (19-65). Twenty-nine (70.7%) patients had SS genotype. Eleven patients had WMLs (26.8%). Patients with WMLs were significantly older (p < 0.001), had a lower HF (p < 0.005) and an impaired cerebral arterial compliance (p < 0.014). The receiver operating curve for the regression model including age and HF showed a higher area under the curve compared to age alone (0.946 vs. 0.876). BHT and Mx did not significantly differ between the two groups.

CONCLUSIONS

Lower parasympathetic activity and impaired cerebral arterial compliance were associated with WMLs in adults with SCD. This could potentially yield to a better understanding of pathophysiological parameters leading to premature cerebrovascular ageing in SCD.

Autonomic and Vascular Responses during Reactive Hyperemia in Healthy Individuals and Patients with Sickle Cell Anemia

Background and Objectives: To compare autonomic and vascular responses during reactive hyperemia (RH) between healthy individuals and patients with sickle cell anemia (SCA). Materials and Methods: Eighteen healthy subjects and 24 SCA patients were subjected to arterial occlusion for 3 min at the lower right limb level. The pulse rate variability (PRV) and pulse wave amplitude were measured through photoplethysmography using the Angiodin^® PD 3000 device, which was placed on the first finger of the lower right limb 2 min before (Basal) and 2 min after the occlusion. Pulse peak intervals were analyzed using time-frequency (wavelet transform) methods for high-frequency (HF: 0.15-0.4) and low-frequency (LF: 0.04-0.15) bands, and the LF/HF ratio was calculated. Results: The pulse wave amplitude was higher in healthy subjects compared to SCA patients, at both baseline and post-occlusion (p < 0.05). Time-frequency analysis showed that the LF/HF peak in response to the post-occlusion RH test was reached earlier in healthy subjects compared to SCA patients. Conclusions: Vasodilatory function, as measured by PPG, was lower in SCA patients compared to healthy subjects. Moreover, a cardiovascular autonomic imbalance was present in SCA patients with high sympathetic and low parasympathetic activity in the basal state and a poor response of the sympathetic nervous system to RH. Early cardiovascular sympathetic activation (10 s) and vasodilatory function in response to RH were impaired in SCA patients.

Adverse childhood experiences in children and adolescents with sickle cell disease: A retrospective cohort study

BACKGROUND

Adverse childhood experiences (ACEs) are linked to poor health outcomes; however, the relationship between ACEs and health outcomes among children and adolescents with sickle cell disease (SCD) has limited documentation in the published literature.

PROCEDURE

This retrospective cohort study involved 45 children and 30 adolescents. Participants were screened using the Center for Youth Wellness ACE Questionnaire. Parents completed the questionnaire for children. Adolescents provided self-report. ACEs were treated as continuous and categorical scales: 0-1 verus ≥2 original ACEs (individual and/or familial level); 0-1 versus ≥2 additional ACEs (community level); and 0-3 versus ≥4 expanded ACEs (original + additional). Pain and acute chest syndrome events were compared using Wilcoxon rank-sum tests, and correlated with cumulative ACE scores using Spearman's correlation. Multivariable models were fitted to examine the association between ACEs and pain/acute chest syndrome.

RESULTS

The cumulative number of original ACEs positively correlated with acute chest syndrome events (rho = .53, p = .003) and pain (rho = .40, p = .028) among adolescents. Adolescents with ≥2 versus 0-1 original ACEs had a higher number of acute chest syndrome events (4.9 ± 2.6 vs. 1.6 ± 2.2, p = .002); however, this association was confounded by asthma. Acute chest syndrome events and hospitalizations for pain did not differ among child ACE groups. Emergency department (ED) pain visits were higher among children with ≥4 versus 0-3 expanded ACEs (1.6 ± 2.8 vs. 3.3 ± 3.2, p = .042), even after controlling for SCD genotype, asthma, disease-modifying treatment, and follow-up years (p = .027).

CONCLUSION

ACEs are linked to increased morbidity among children and adolescents with SCD. Prospective studies are needed to further understand this relationship and test ACE-protective remedies.

Heart rate variability associated with acute exercise challenge in children with sickle cell anaemia

We examined heart rate variability (HRV) during exercise testing in 20 children with sickle cell anaemia (SCA) and 12 controls. Subjects achieved lower median HRV at peak exercise [standard deviation of R-wave to R-wave intervals (SDNN), 2·3 vs 2·9 ms, P = 0·027; logarithmic transformation of high frequency power (lnHF), 0·9 vs 1·3 ln(ms² ), P = 0·047] and had lower post-exercise HRV across minute-by-minute analysis of recovery. After adjustment for haemoglobin, fitness and SCA status, subjects had lower HRV at the end of recovery with differences increasing as baseline HRV increased. Further investigation of HRV and exercise safety in SCA is warranted.

Infant weight-for-length gain associated with autonomic nervous system reactivity

BACKGROUND

Research suggests that children's health and well-being are supported by core adaptive systems, including the autonomic nervous system (ANS). Despite evidence for the importance of adulthood ANS regulation in the development of disease, few studies have examined how early development may influence emerging ANS function. Therefore, we examined how infant adiposity gain during early infancy related to ANS regulation at 6 months.

METHODS

Infant weight and length were abstracted from birth records and measured during the 6-month assessment in a low-income, racially/ethnically diverse sample (N = 60). WHO-standardized weight-for-length-gain change was calculated across the first 6 months of life. ANS reactivity was measured as the combined sympathetic (i.e., pre-ejection period) and parasympathetic (i.e., respiratory sinus arrhythmia) nervous system responses during the developmentally challenging Still Face Paradigm (SFP). ANS "classic reactivity" response was characterized by paired sympathetic activation and parasympathetic withdrawal.

RESULTS

Lower weight-for-length gain in the first 6 months predicted classic reactivity during still face. However, greater weight-for-length gain predicted "classic reactivity" during the reunion, when infants were expected to recover, suggesting autonomic dysregulation.

CONCLUSIONS

These findings suggest an association between early life adiposity gain and the development of infant ANS regulation.

IMPACT

Adiposity gain during early infancy was associated with autonomic nervous system regulation at 6 months. This study identifies early adiposity gain (greater than average infant weight-for-length gain) as a risk for ANS dysregulation. This research focuses on a critical developmental period of ANS plasticity. If confirmed, findings can be used to inform early intervention programs targeting obesity prevention and to promote self-regulation.

"A child with sickle cell disease can't live with just anyone." A mixed methods study of socio-behavioral influences and severity of sickle cell disease in northern Nigeria

BACKGROUND

The modulatory effects of psychosocial and biophysical environments on sickle cell disease (SCD) severity during childhood has not been well characterized in high burden settings, such as Nigeria.

OBJECTIVES

We identified socio-demographic correlates and explored caregivers' perceptions on socio-behavioral and environmental influences on hospitalization for pain and blood transfusion of children with SCD in Kano, Nigeria.

METHODS

Using mixed methods, structured questionnaires were administered to a clinic-based sample of caregivers of children with SCD (n = 372), complemented with eight focus group discussions. Binary logistic regression models and the framework approach were used to analyze the data.

RESULTS

The majority (73.1%, n = 272) of the children had at least one vaso-occlusive crisis (VOC), and 41.1% (n = 153) required hospitalization in the preceding year. A total of 170 children (45.7%) received blood transfusion. Hospitalization was predicted by the child's age (Adjusted Odds Ratio, AOR = 1.89; 95% Confidence Interval, CI: 1.18-4.07, ≥10 vs <5 years), relationship with caregiver (AOR = 5.41; 95%CI: 1.17-25.05, mother vs "others"), father's number of children (AOR = 2.21; 95%CI: 1.19-5.31, ≥10 vs ≤4), and siblings with SCD (AOR = 2.36; 95%CI: 1.16-8.80, 2 vs 0). Caregivers perceived maternal care, stable home environment, medication adherence, anti-mosquito measures, and adequate nutrition as protective factors, whereas poverty, extreme emotions, physical exertion, and extreme temperatures were identified as detrimental to the health of the child.

CONCLUSIONS

Hospitalizations for VOC and transfusion rates among children with SCD were high. Understanding the modulatory effects of socio-behavioral factors on SCD severity could inform preventive measures and enhance the quality of life of affected children.

Progressive vasoconstriction with sequential thermal stimulation indicates vascular dysautonomia in sickle cell disease

Persons with sickle cell disease (SCD) exhibit subjective hypersensitivity to cold and heat perception in experimental settings, and triggers such as cold exposure are known to precipitate vaso-occlusive crises by still unclear mechanisms. Decreased microvascular blood flow (MBF) increases the likelihood of vaso-occlusion by increasing entrapment of sickled red blood cells in the microvasculature. Because those with SCD have dysautonomia, we anticipated that thermal exposure would induce autonomic hypersensitivity of their microvasculature with an increased propensity toward vasoconstriction. We exposed 17 patients with SCD and 16 control participants to a sequence of predetermined threshold temperatures for cold and heat detection and cold and heat pain via a thermode placed on the right hand. MBF was measured on the contralateral hand by photoplethysmography, and cardiac autonomic balance was assessed by determining heart rate variability. Thermal stimuli at both detection and pain thresholds caused a significant decrease in MBF in the contralateral hand within seconds of stimulus application, with patients with SCD showing significantly stronger vasoconstriction (P = .019). Furthermore, patients with SCD showed a greater progressive decrease in blood flow than did the controls, with poor recovery between episodes of thermal stimulation (P = .042). They had faster vasoconstriction than the controls (P = .033), especially with cold detection stimulus. Individuals with higher anxiety also experienced more rapid vasoconstriction (P = .007). Augmented vasoconstriction responses and progressive decreases in perfusion with repeated thermal stimulation in SCD are indicative of autonomic hypersensitivity in the microvasculature. These effects are likely to increase red cell entrapment in response to clinical triggers such as cold or stress, which have been associated with vaso-occlusive crises in SCD.

Cardiovascular Sequelae of Sickle Cell Disease

Sickle cell disease (SCD) is one of the most common hereditary hemoglobinopathies worldwide. It is a multisystem disease that causes considerable patient morbidity. Despite advances in medical treatment, cardiopulmonary complications remain the most common cause of death in individuals with SCD. A growing body of evidence has shown that SCD results in a spectrum of cardiovascular complications through a variety of mechanisms, including chronic hemolysis, local tissue hypoxia, increased oxidative stress, and autonomic instability. Herein, we will examine the pathophysiology of sickle cell vasculopathy and discuss the spectrum of cardiovascular sequelae of the disease, while highlighting the impact of SCD on the cardiovascular health of the patients.

Autonomically-mediated decrease in microvascular blood flow due to mental stress and pain in sickle cell disease: A target for neuromodulatory interventions

Pain and vaso-occlusive crises (VOC) are hallmark complications of sickle cell disease (SCD) and result in significant physical and psychosocial impairment. The variability in SCD pain frequency and triggers for the transition from steady state to VOC are not well understood. This paper summarizes the harmful physiological effects of pain and emotional stressors on autonomically-mediated vascular function in individuals with SCD and the effects of a cognitive, neuromodulatory intervention (i.e. hypnosis) on microvascular blood flow. We reviewed recent studies from the authors' vascular physiology laboratory that assessed microvascular responses to laboratory stressors in individuals with SCD. Results indicate that participants with SCD exhibit marked neurally mediated vascular reactivity in response to pain, pain-related fear, and mental stress. Further, pilot study results show that engagement in hypnosis may attenuate harmful microvascular responses to pain. The collective results demonstrate that autonomically-mediated vascular responses to pain and mental stress represent an important SCD intervention target. This ongoing work provides physiological justification for the inclusion of cognitive, neuromodulatory and complementary treatments in SCD disease management and may inform the development of targeted, integrative interventions that prevent the enhancement of autonomic vascular dysfunction in SCD.

Salbutamol Worsens the Autonomic Nervous System Dysfunction of Children With Sickle Cell Disease

Background

Sickle cell disease (SCD) patients with asthma have an increased rate of vaso-occlusive crisis (VOC) and acute chest syndrome (ACS) episodes when compared to those without asthma. We hypothesized that either asthma diagnosis or bronchodilator treatment might aggravate SCD via their modulating effect on the autonomic nervous system (ANS).

Methods

Cross-sectional evaluation of heart rate variability (HRV) during pulmonary function tests, including salbutamol administration, in children with SCD receiving asthma treatment or not when compared to asthmatic children without SCD matched for ethnicity.

Results

SCD children with asthma (n = 30, median age of 12.9 years old) were characterized by a reduced FEV₁/FVC ratio, an increased bronchodilator response, and a greater incidence of VOC and ACS when compared to SCD children without asthma (n = 30, 12.7 years). Children with asthma without SCD (n = 29, 11.4 years) were characterized by a higher exhaled NO fraction than SCD children. SCD children when compared to non-SCD children showed reduced HRV [total power, low (LF) and high (HF, vagal tone) frequencies], which was further worsened by salbutamol administration in all the groups: reduction in total power and HF with an increase in LF/HF ratio. After salbutamol, the LF/HF ratio of the SCD children was higher than that of the non-SCD children. The two groups of SCD children were similar, suggesting that asthma diagnosis per se did not modify ANS functions.

Conclusion

SCD children are characterized by impaired parasympathetic control and sympathetic overactivity that is worsened by salbutamol administration.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT04062409.

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.

Frequency of Interleukins IL1ß/IL18 and Inflammasome NLRP1/NLRP3 Polymorphisms in Sickle Cell Anemia Patients and their Association with Severity Score

BACKGROUND

Interleukins IL1ß/IL18 and Inflammasome NLRP1/NLRP3 polymorphisms can change the course of multiple human diseases, both inflammatory as infectious. SNPs these proteins were associated with the constructive activation of the Inflammasome and excessive production of IL-1β induce a serious autoinflammatory disease, as sickle cell anemia (SCA). The present study aims to association of interleukins IL1ß/IL18 and inflammasome NLRP1/NLRP3 polymorphisms in SCA patients in Amazon region and their association with severity score.

METHODS

The study was developed at Fundação Hospitalar de Hematologia e Hemoterapia do Amazonas (HEMOAM) with 21 patients diagnosed SCA (HbSS) and 50 Healthy Donor´s. Genetic polymorphisms (SNPs) in interleukins IL1ß/IL18 and inflammasome NLRP1/NLRP3 were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and real time PCR. Simple and multiple logistic regression were performed to investigate association between the polymorphisms and the SCA and severe score.

RESULTS

The genotypes C/C (IL18 -137G/C) and C/A (NLRP3, rs35829419) appear to be risk factors for SCA disease (IL18: G/G vs C/C OR=103.500 [95% CI: 8.32-1287.79, p<0.00001]; IL18: G/G vs G/C OR=7.360 [95% CI: 0.85-63.48, p=0.040]; IL18: G/G vs CC+CG OR=14.481 [95% CI: 1.79-117.32, p=0.002; NLRP3: C/C vs C/A: OR=10.967 [95% CI: 2.41-49.89, p=0.0004]). In addition, only allelic C (IL18 -137G/C) and A (NLRP3) appear to be risk factors for SCA disease (IL18: G vs C OR=6.366 [95% CI: 2.73-14.86, p<0.00001]; NLRP3: C vs A OR=8.383 [95% CI: 2.03-34.62, p=0.005]. No associations were observed between genotypes and alleles with the severity score.

CONCLUSION

Evidence of association between the IL18 (rs16944) and NLRP3 (rs35829419) polymorphisms with sickle cell anemia were described. Our results suggest that individuals with genotypes evaluated are associated SCA disease even though it does not influence the severe score.

Respiratory Sinus Arrhythmia Acts as a Moderator of the Relationship Between Parental Marital Conflict and Adolescents' Internalizing Problems

The present study examined the potential moderating role respiratory sinus arrhythmia (RSA) plays in the relationship between parental marital conflict and adolescents' internalizing problems. To examine this issue, data were collected from 330 adolescents (13-14 years, 182 boys). The Chinese version of the Achenbach Youth Self-Report-2001 and the Chinese version of the Children's Perception of Interparental Conflict were used to assess the adolescents' internalizing problems and their perceptions of parental marital conflict. To obtain RSA data, electrocardiogram monitoring was performed on the adolescents at baseline and during a series of stress tasks (watching a film clip depicting marital conflict, a mental arithmetic task, and a speech task). The results indicated that baseline RSA and RSA reactivity to the film clip moderated the relationship between parental marital conflict and internalizing problems in early adolescents. The moderating effect of baseline RSA supported the BSCT hypothesis. Specifically, adolescents with low baseline RSA have both the highest and lowest levels of internalizing problems, depending on the level of marital conflict. In contrast, adolescents with high levels of baseline RSA have moderate levels in internalizing problems, regardless of the level of marital conflict they experience. Similarly, high marital conflict was related to internalizing problems for adolescents with less RSA suppression or RSA augmentation but not for those with greater RSA suppression. This effect was specific to stress related to marital conflict, as RSA reactivity to the mental arithmetic task and speech task did not moderate the relationship between marital conflict and internalizing problems. These findings suggest that certain profile of parasympathetic nervous activity is a risk factor for internalizing problems particularly for those who experience high-conflict environments.

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.

Mental stress causes vasoconstriction in subjects with sickle cell disease and in normal controls

Vaso-occlusive crisis (VOC) is a hallmark of sickle cell disease (SCD) and occurs when deoxygenated sickled red blood cells occlude the microvasculature. Any stimulus, such as mental stress, which decreases microvascular blood flow will increase the likelihood of red cell entrapment resulting in local vaso-occlusion and progression to VOC. Neurally mediated vasoconstriction might be the physiological link between crisis triggers and vaso-occlusion. In this study, we determined the effect of mental stress on microvascular blood flow and autonomic nervous system reactivity. Sickle cell patients and controls performed mentally stressful tasks, including a memory task, conflict test and pain anticipation test. Blood flow was measured using photoplethysmography, autonomic reactivity was derived from electrocardiography and perceived stress was measured by the State-Trait Anxiety Inventory questionnaire. Stress tasks induced a significant decrease in microvascular blood flow, parasympathetic withdrawal and sympathetic activation in all subjects. Of the various tests, pain anticipation caused the highest degree of vasoconstriction. The magnitude of vasoconstriction, sympathetic activation and perceived stress was greater during the Stroop conflict test than during the N-back memory test, indicating the relationship between magnitude of experimental stress and degree of regional vasoconstriction. Baseline anxiety had a significant effect on the vasoconstrictive response in sickle cell subjects but not in controls. In conclusion, mental stress caused vasoconstriction and autonomic nervous system reactivity in all subjects. Although the pattern of responses was not significantly different between the two groups, the consequences of vasoconstriction can be quite significant in SCD because of the resultant entrapment of sickle cells in the microvasculature. This suggests that mental stress can precipitate a VOC in SCD by causing neural-mediated vasoconstriction.

Sickle Cell Disease Subjects Have a Distinct Abnormal Autonomic Phenotype Characterized by Peripheral Vasoconstriction With Blunted Cardiac Response to Head-Up Tilt

In sickle cell disease (SCD), prolonged capillary transit times, resulting from reduced peripheral blood flow, increase the likelihood of rigid red cells entrapment in the microvasculature, predisposing to vaso-occlusive crisis. Since changes in peripheral flow are mediated by the autonomic nervous system (ANS), we tested the hypothesis that the cardiac and peripheral vascular responses to head-up tilt (HUT) are abnormal in SCD. Heart rate, respiration, non-invasive continuous blood pressure and finger photoplethysmogram (PPG) were monitored before, during, and after HUT in SCD, anemic controls and healthy subjects. Percent increase in heart rate from baseline was used to quantify cardiac ANS response, while percent decrease in PPG amplitude represented degree of peripheral vasoconstriction. After employing cluster analysis to determine threshold levels, the HUT responses were classified into four phenotypes: (CP) increased heart rate and peripheral vasoconstriction; (C) increased heart rate only; (P) peripheral vasoconstriction only; and (ST) subthreshold cardiac and peripheral vascular responses. Multinomial logistic regression (MLR) was used to relate these phenotypic responses to various parameters representing blood properties and baseline cardiovascular activity. The most common phenotypic response, CP, was found in 82% of non-SCD subjects, including those with chronic anemia. In contrast, 70% of SCD subjects responded abnormally to HUT: C-phenotype = 22%, P-phenotype = 37%, or ST-phenotype = 11%. MLR revealed that the HUT phenotypes were significantly associated with baseline cardiac parasympathetic activity, baseline peripheral vascular variability, hemoglobin level and SCD diagnosis. Low parasympathetic activity at baseline dramatically increased the probability of belonging to the P-phenotype in SCD subjects, even after adjusting for hemoglobin level, suggesting a characteristic autonomic dysfunction that is independent of anemia. Further analysis using a mathematical model of heart rate variability revealed that the low parasympathetic activity in P-phenotype SCD subjects was due to impaired respiratory-cardiac coupling rather than reduced cardiac baroreflex sensitivity. By having strong peripheral vasoconstriction without compensatory cardiac responses, P-phenotype subjects may be at increased risk for vaso-occlusive crisis. The classification of autonomic phenotypes based on HUT response may have potential use for guiding therapeutic interventions to alleviate the risk of adverse outcomes in SCD.

Objectively measured physical activity levels and sedentary time in children and adolescents with sickle cell anemia

The aim of this study was to identify the levels of physical activity and sedentary behaviour of children and adolescents with sickle cell disease (SCA) compared to healthy individuals. A cross-sectional study with a quantitative approach was performed at a reference center for the treatment of patients with hemoglobinopathies in northeastern Brazil. Patients were recruited between October 2015 and January 2017. Eligible participants answered a Physical Activity Questionnaire for Older Children and Adolescents (PAQ-C) and were instructed to use an ActiGraph wGT3X-BT triaxial accelerometer for seven consecutive days. Fifty patients (and their 50 controls matched for age and sex) were then evaluated. We observed lower moderate (19.2 ± 11.9 and 27.1 ± 13.8 min/d; p<0.01) and vigorous PA (3.6 ± 4.1 and 7.8 ± 7.4 min/d; p<0.01) in cases than controls, respectively. There was also a significant difference among cases and controls in the following variables: total of steps (51010 ± 19600 and 59105 ± 22650; p = 0.04) and "total caloric expenditure" (1015 ± 516 and 2404 ± 1308; p<0.01), with the lowest values for the patients with SCA for all variables. Children and adolescents with SCA presented lower levels of physical activity than healthy children and adolescents, either when evaluated by PAQs or by accelerometer.

Muscle Strength, Power, and Torque Deficits in Children With Type SS Sickle Cell Disease

In African-American children aged 5 to 17 years with and without type SS sickle cell disease (SCD-SS), dominant hand maximal handgrip strength, peak power, and plantar flexion isometric maximal voluntary contraction (MVC) torque were compared with adjustments for body size and composition. Children with SCD-SS (n=21; age, 11±1 y) compared with healthy control children (n=23; 10±1 y) did not differ by age, sex, or maturation stage, but had significantly lower Z scores for height, weight, body mass index, arm circumference, upper arm muscle area, and lean mass-for-height. Children with SCD-SS had significantly lower unadjusted handgrip strength (16±2 vs. 23±2 kg, P<0.01), peak power (1054±107 vs. 1488±169 W, P<0.04) and MVC torques at 2 angles (10 degrees: 27±3 vs. 42±5 Nm; 20 degrees: 21±3 vs. 34±4 Nm; all P<0.05). Performance decrements persisted when handgrip strength was adjusted for lean body mass and fat mass explaining 66% of the variance; peak power adjusted for age, lean body mass, fat mass, and height explaining 91% of the variance; and the highest MVC torque (10-degree angle) adjusted for left leg length, lean mass-for-height, and fat mass-for-height Z scores explaining 65% of the variance. This suggests additional factors contribute to the attenuated anaerobic performance.

Individuals with sickle cell disease have a significantly greater vasoconstriction response to thermal pain than controls and have significant vasoconstriction in response to anticipation of pain

The painful vaso-occlusive crises (VOC) that characterize sickle cell disease (SCD) progress over hours from the asymptomatic steady-state. SCD patients report that VOC can be triggered by stress, cold exposure, and, pain itself. We anticipated that pain could cause neural-mediated vasoconstriction, decreasing regional blood flow and promoting entrapment of sickle cells in the microvasculature. Therefore, we measured microvascular blood flow in the fingers of both hands using plethysmography and laser-Doppler flowmetry while applying a series of painful thermal stimuli on the right forearm in 23 SCD patients and 25 controls. Heat pain applied to one arm caused bilateral decrease in microvascular perfusion. The vasoconstriction response started before administration of the thermal pain stimulus in all subjects, suggesting that pain anticipation also causes significant vasoconstriction. The time delay between thermal pain application and global vasoconstriction ranged from 5 to 15.5 seconds and increased with age (P < .01). Although subjective measures, pain threshold and pain tolerance were not different between SCD subjects and controls, but the vaso-reactivity index characterizing the microvascular blood flow response to painful stimuli was significantly higher in SCD patients (P = .0028). This global vasoconstriction increases microvascular transit time, and may promote entrapment of sickle cells in the microvasculature, making vaso-occlusion more likely. The rapidity of the global vasoconstriction response indicates a neural origin that may play a part in the transition from steady-state to VOC, and may also contribute to the variability in VOC frequency observed in SCD patients.

Contrasting resting-state fMRI abnormalities from sickle and non-sickle anemia

Sickle cell disease (SCD) is a chronic blood disorder that is often associated with acute and chronic cerebrovascular complications, including strokes and impaired cognition. Using functional resting state magnetic resonance images, we performed whole-brain analysis of the amplitude of low frequency fluctuations (ALFF), to detect areas of spontaneous blood oxygenation level dependent signal across brain regions. We compared the ALFF of 20 SCD patients to that observed in 19 healthy, age and ethnicity-matched, control subjects. Significant differences were found in several brain regions, including the insula, precuneus, anterior cingulate cortex and medial superior frontal gyrus. To identify the ALFF differences resulting from anemia alone, we also compared the ALFF of SCD patients to that observed in 12 patients having comparable hemoglobin levels but lacking sickle hemoglobin. Increased ALFF in the orbitofrontal cortex and the anterior and posterior cingulate cortex and decreased ALFF in the frontal pole, cerebellum and medial superior frontal gyrus persisted after accounting for the effect of anemia. The presence of white matter hyperintensities was associated with depressed frontal and medial superior frontal gyri activity in the SCD subjects. Decreased ALFF in the frontal lobe was correlated with decreased verbal fluency and cognitive flexibility. These findings may lead to a better understanding of the pathophysiology of SCD.

Children's Autonomic Nervous System Reactivity Moderates the Relations between Family Adversity and Sleep Problems in Latino 5-Year Olds in the CHAMACOS Study

Sleep problems are common for young children especially if they live in adverse home environments. Some studies investigate if young children may also be at a higher risk of sleep problems if they have a specific biological sensitivity to adversity. This paper addresses the research question, does the relations between children’s exposure to family adversities and their sleep problems differ depending on their autonomic nervous system’s sensitivity to challenges? As part of a larger cohort study of Latino, low-income families, we assessed the cross-sectional relations among family demographics (education, marital status), adversities [routines, major life events (MLE)], and biological sensitivity as measured by autonomic nervous system (ANS) reactivity associated with parent-rated sleep problems when the children were 5 years old. Mothers were interviewed in English or Spanish and completed demographic, family, and child measures. The children completed a 15-min standardized protocol while continuous cardiac measures of the ANS [respiratory sinus arrhythmia (RSA), preejection period (PEP)] were collected during resting and four challenge conditions. Reactivity was defined as the mean of the responses to the four challenge conditions minus the first resting condition. Four ANS profiles, co-activation, co-inhibition, reciprocal low RSA and PEP reactivity, and reciprocal high RSA and PEP reactivity, were created by dichotomizing the reactivity scores as high or low reactivity. Logistic regression models showed there were significant main effects for children living in families with fewer daily routines having more sleep problems than for children living in families with daily routines. There were significant interactions for children with low PEP reactivity and for children with the reciprocal, low reactivity profiles who experienced major family life events in predicting children’s sleep problems. Children who had a reciprocal, low reactivity ANS profile had more sleep problems if they also experienced MLE than children who experienced fewer MLE. These findings suggest that children who experience family adversities have different risks for developing sleep problems depending on their biological sensitivity. Interventions are needed for young Latino children that support family routines and reduce the impact of family adversities to help them develop healthy sleep practices.

Biophysical markers of the peripheral vasoconstriction response to pain in sickle cell disease

Painful vaso-occlusive crisis (VOC), a complication of sickle cell disease (SCD), occurs when sickled red blood cells obstruct flow in the microvasculature. We postulated that exaggerated sympathetically mediated vasoconstriction, endothelial dysfunction and the synergistic interaction between these two factors act together to reduce microvascular flow, promoting regional vaso-occlusions, setting the stage for VOC. We previously found that SCD subjects had stronger vasoconstriction response to pulses of heat-induced pain compared to controls but the relative degrees to which autonomic dysregulation, peripheral vascular dysfunction and their interaction are present in SCD remain unknown. In the present study, we employed a mathematical model to decompose the total vasoconstriction response to pain into: 1) the neurogenic component, 2) the vascular response to blood pressure, 3) respiratory coupling and 4) neurogenic-vascular interaction. The model allowed us to quantify the contribution of each component to the total vasoconstriction response. The most salient features of the components were extracted to represent biophysical markers of autonomic and vascular impairment in SCD and controls. These markers provide a means of phenotyping severity of disease in sickle-cell anemia that is based more on underlying physiology than on genotype. The marker of the vascular component (BM_v) showed stronger contribution to vasoconstriction in SCD than controls (p = 0.0409), suggesting a dominant myogenic response in the SCD subjects as a consequence of endothelial dysfunction. The marker of neurogenic-vascular interaction (BM_n-v) revealed that the interaction reinforced vasoconstriction in SCD but produced vasodilatory response in controls (p = 0.0167). This marked difference in BM_n-v suggests that it is the most sensitive marker for quantifying combined alterations in autonomic and vascular function in SCD in response to heat-induced pain.

Physical activity level is not a determinant of autonomic nervous system activity and clinical severity in children/adolescents with sickle cell anemia: A pilot study

BACKGROUND

Autonomic nervous system (ANS) activity has been suggested to modulate the clinical severity of sickle cell anemia (SCA) by increasing the risk for vaso-occlusive events. Regular physical activity (PA) is known to improve ANS activity and health status in several cardiovascular and metabolic diseases. Whether regular PA improves the health status of SCA patients remains unknown.

PROCEDURE

Twenty-two patients with SCA and 15 healthy (AA) children/adolescents participated to the study. Heart rate variability was measured in supine position and after a tilt-test to quantify the ANS activity. PA energy expenditure (PAEE) was assessed with questionnaire.

RESULTS

1) PAEE was lower in SCA compared to AA (190 ± 152 vs. 432 ± 277 kcal · d(-1), respectively, P < 0.01), 2) overall ANS activity was lower in SCA compared to AA, 3) parasympathetic withdrawal was observed in SCA with aging, 4) ANS reactivity was slightly impaired in SCA compared to AA (reduction in HFnu: -38 ± 27 vs. -58 ± 14%, respectively, P < 0.05), 5) ANS indices, PAEE, and rates of clinical events were not correlated.

CONCLUSION

Both the level of PA and ANS activity are reduced in SCA compared to AA children/adolescents, particularly in those older than 15 years. Neither PAEE, nor ANS activity seem to influence the clinical severity of children/adolescents with SCA.

Autonomic responses to cold face stimulation in sickle cell disease: a time-varying model analysis

Sickle cell disease (SCD) is characterized by sudden onset of painful vaso-occlusive crises (VOC), which occur on top of the underlying chronic blood disorder. The mechanisms that trigger VOC remain elusive, but recent work suggests that autonomic dysfunction may be an important predisposing factor. Heart-rate variability has been employed in previous studies, but the derived indices have provided only limited univariate information about autonomic cardiovascular control in SCD. To circumvent this limitation, a time-varying modeling approach was applied to investigate the functional mechanisms relating blood pressure (BP) and respiration to heart rate and peripheral vascular resistance in healthy controls, untreated SCD subjects and SCD subjects undergoing chronic transfusion therapy. Measurements of respiration, heart rate, continuous noninvasive BP and peripheral vascular resistance were made before, during and after the application of cold face stimulation (CFS), which perturbs both the parasympathetic and sympathetic nervous systems. Cardiac baroreflex sensitivity estimated from the model was found to be impaired in nontransfused SCD subjects, but partially restored in SCD subjects undergoing transfusion therapy. Respiratory-cardiac coupling gain was decreased in SCD and remained unchanged by chronic transfusion. These results are consistent with autonomic dysfunction in the form of impaired parasympathetic control and sympathetic overactivity. As well, CFS led to a significant reduction in vascular resistance baroreflex sensitivity in the nontransfused SCD subjects but not in the other groups. This blunting of the baroreflex control of peripheral vascular resistance during elevated sympathetic drive could be a potential factor contributing to the triggering of VOC in SCD.

Dexmedetomidine ameliorates nocifensive behavior in humanized sickle cell mice

Patients with sickle cell disease (SCD) can have recurrent episodes of vaso-occlusive crises, which are associated with severe pain. While opioids are the mainstay of analgesic therapy, in some patients, increasing opioid use results in continued and increasing pain. Many believe that this phenomenon results from opioid-induced tolerance or hyperalgesia or that SCD pain involves non-opioid-responsive mechanisms. Dexmedetomidine, a specific α2-adrenoreceptor agonist, which has sedative and analgesic properties, reduces opioid requirements, and can facilitate opioid withdrawal in clinical settings. We hypothesized that dexmedetomidine would ameliorate the nociception phenotype of SCD mice. Townes and BERK SCD mice, strains known to have altered nociception phenotypes, were used in a crossover preclinical trial that measured nocifensive behavior before and after treatment with dexmedetomidine or vehicle. In a linear dose-effect relationship, over 60-min, dexmedetomidine, compared with vehicle, significantly increased hot plate latency in Townes and BERK mice (P≤0.006). In sickle, but not control mice, dexmedetomidine improved grip force, an indicator of muscle pain (P=0.002). As expected, dexmedetomidine had a sedative effect in sickle and control mice as it decreased wakefulness scores compared with vehicle (all P<0.001). Interestingly, the effects of dexmedetomidine on hot plate latency and wakefulness scores were different in sickle and control mice, i.e., dexmedetomidine-related increases in hotplate latency and decreases in wakefulness scores were significantly smaller in Townes sickle compared to control mice. In conclusion, these findings of beneficial effects of dexmedetomidine on the nociception phenotype in SCD mice might support the conduct of studies of dexmedetomidine in SCD patients.

Severity of Brazilian sickle cell disease patients: severity scores and feasibility of the Bayesian network model use

The integration of the several clinical and laboratory dimensions and the influence of each parameter on the sickle cell disease (SCD)-related mortality is useful for predicting the phenotype of an individual. This study evaluated the feasibility of the SCD severity calculator use to measure disease severity in Brazilian patients. The study group was composed of 500 SCD patients (440 HbSS and 60 HbSC) diagnosed by molecular biology. We observed a decrease in severity scores in 72 SCD patients assessed before and after the hydroxyurea (HU) use. Furthermore, the HU influenced the increase of mean corpuscular volume (MCV) and HbF concentration, and the decrease of leukocytes and total bilirubin. We found 180 (36.0%) patients with intermediate phenotype, 170 (34.0%) mild phenotype and 150 (30.0%) with severe phenotype. Patients with ages >40 years had higher mean score (0.778±0.177) than patients between 18 and 40 years (0.562±0.152) and patients between 5 and 17 years (0.322±0.145). We observe that there is a tendency of individuals with leg ulcers, avascular necrosis and cardiac complications with increasing age. Correlation analysis showed relations between severity scores with leukocytes, reticulocytes, bilirubin, lactate dehydrogenase, HbS, hemoglobin and hematocrit (p<0.05). Several comparisons involving age groups, SCD genotype and phenotypic classification had satisfactory results and this classification will be used for future studies involving genetic polymorphisms, response to treatment with HU and oxidative stress markers in SCD.

Acute moderate exercise does not further alter the autonomic nervous system activity in patients with sickle cell anemia

A decreased global autonomic nervous system (ANS) activity and increased sympathetic activation in patients with sickle cell anemia (SCA) seem to worsen the clinical severity and could play a role in the pathophysiology of the disease, notably by triggering vaso-occlusive crises. Because exercise challenges the ANS activity in the general population, we sought to determine whether a short (<15 min) and progressive moderate exercise session conducted until the first ventilatory threshold had an effect on the ANS activity of a group of SCA patients and a group of healthy individuals (CONT group). Temporal and spectral analyses of the nocturnal heart rate variability were performed before and on the 3 nights following the exercise session. Standard deviation of all normal RR intervals (SDNN), total power, low frequencies (LF) and high frequencies powers (HF) were lower but LF/HF was higher in SCA patients than in the CONT group. Moderate exercise did not modify ANS activity in both groups. In addition, no adverse clinical events occurred during the entire protocol. These results imply that this kind of short and moderate exercise is not detrimental for SCA patients.

Cardiac vagal control and children's adaptive functioning: a meta-analysis

Polyvagal theory has influenced research on the role of cardiac vagal control, indexed by respiratory sinus arrhythmia withdrawal (RSA-W) during challenging states, in children's self-regulation. However, it remains unclear how well RSA-W predicts adaptive functioning (AF) outcomes and whether certain caveats of measuring RSA (e.g., respiration) significantly impact these associations. A meta-analysis of 44 studies (n=4996 children) revealed small effect sizes such that greater levels of RSA-W were related to fewer externalizing, internalizing, and cognitive/academic problems. In contrast, RSA-W was differentially related to children's social problems according to sample type (community vs. clinical/at-risk). The relations between RSA-W and children's AF outcomes were stronger among studies that co-varied baseline RSA and in Caucasian children (no effect was found for respiration). Children from clinical/at-risk samples displayed lower levels of baseline RSA and RSA-W compared to children from community samples. Theoretical/practical implications for the study of cardiac vagal control are discussed.

Peripheral vascular response to inspiratory breath hold in paediatric homozygous sickle cell disease

New Findings

• What is the central question of this study?

Autonomic nervous dysfunction is implicated in complications of sickle cell anaemia (SCA). In healthy adults, a deep inspiratory breath hold (IBH) elicits rapid transient SNS- mediated vasoconstriction detectable using Laser Doppler Flux (LDF) assessment of the finger-tip cutaneous micovasculature.

• What is the main finding and its importance?

We demonstrate significantly increased resting peripheral blood flow and sympathetic activity in African children with SCA compared to sibling controls and increased sympathetic stimulation in response to vasoprovocation with DIG.

This study is the first to observe an inverse association between resting peripheral blood flow and haemoglobin oxygen saturation (SpO2). These phenomena may be an adaptive response to the hypoxic exposure in SCA.

There is increasing evidence that autonomic dysfunction in adults with homozygous sickle cell (haemoglobin SS) disease is associated with enhanced autonomic nervous system-mediated control of microvascular perfusion. However, it is unclear whether such differences are detectable in children with SS disease. We studied 65 children with SS disease [38 boys; median age 7.2 (interquartile range 5.1–10.6) years] and 20 control children without symptoms of SS disease [8 boys; 8.7 (5.5–10.8) years] and recorded mean arterial blood pressure (ABP) and daytime haemoglobin oxygen saturation (). Cutaneous blood flux at rest (RBF) and during the sympathetically activated vasoconstrictor response to inspiratory breath hold (IBH) were measured in the finger pulp of the non-dominant hand using laser Doppler fluximetry. Local factors mediating flow motion were assessed by power spectral density analysis of the oscillatory components of the laser Doppler signal. The RBF measured across the two study groups was negatively associated with age (r=−0.25, P < 0.0001), ABP (r=−0.27, P= 0.02) and daytime (r=−0.30, P= 0.005). Children with SS disease had a higher RBF (P= 0.005) and enhanced vasoconstrictor response to IBH (P= 0.002) compared with control children. In children with SS disease, higher RBF was associated with an increase in the sympathetic interval (r=−0.28, P= 0.022). The SS disease status, daytime and age explained 22% of the variance in vasoconstrictor response to IBH (P < 0.0001). Our findings suggest that blood flow and blood flow responses in the skin of young African children with SS disease differ from those of healthy control children, with increased resting peripheral blood flow and increased sympathetic stimulation from a young age in SS disease. They further suggest that the laser Doppler flowmetry technique with inspiratory breath hold manoeuvre appears to be robust for use in young children with SS disease, to explore interactions between , ABP and autonomic function with clinical complications, e.g. skin ulceration.

Developmental changes in autonomic nervous system resting and reactivity measures in Latino children from 6 to 60 months of age

OBJECTIVE

: This study describes the developmental changes and individual stability in autonomic nervous system (ANS) resting and challenge responses for a cohort of primarily Latino, low-income children during the first 5 years of life.

METHODS

: ANS measures of the parasympathetic nervous system (respiratory sinus arrhythmia [RSA]) and sympathetic nervous system (preejection period [PEP]) were collected on a representative sample of the full cohort at 6, 12, 42, and 60 months of age (N = 378). The children participated in a standardized protocol to elicit ANS responses during resting and challenging states. Reactivity profiles were created to summarize each child's combined RSA and PEP reactivity (i.e., change in response to challenges compared to a resting state).

RESULTS

: Results showed developmental changes in ANS measures from 6 to 60 months: heart rate decreased, RSA increased, PEP increased, and frequency of classic reactivity profiles of reciprocal sympathetic activation and parasympathetic withdrawal increased. Correlations showed moderate stability for resting and challenging conditions but not reactivity.

CONCLUSIONS

: These findings suggest that low-income Latino children, from 6 to 60 months of age, showed ANS developmental changes and moderate individual stability for resting and challenge responses but not for reactivity. There was a significant shift in the frequency of children with the classic reactivity profile from 6 by 60 months of age. This is the first cohort study to show the developmental changes in ANS and young children's increase in their biologic sensitivity to the environment during the first 5 years of life.

Peripheral vasoconstriction and abnormal parasympathetic response to sighs and transient hypoxia in sickle cell disease

RATIONALE

Sickle cell disease is an inherited blood disorder characterized by vasoocclusive crises. Although hypoxia and pulmonary disease are known risk factors for these crises, the mechanisms that initiate vasoocclusive events are not well known.

OBJECTIVES

To study the relationship between transient hypoxia, respiration, and microvascular blood flow in patients with sickle cell.

METHODS

We established a protocol that mimics nighttime hypoxic episodes and measured microvascular blood flow to determine if transient hypoxia causes a decrease in microvascular blood flow. Significant desaturations were induced safely by five breaths of 100% nitrogen.

MEASUREMENTS AND MAIN RESULTS

Desaturation did not induce change in microvascular perfusion; however, it induced substantial transient parasympathetic activity withdrawal in patients with sickle cell disease, but not controls subjects. Marked periodic drops in peripheral microvascular perfusion, unrelated to hypoxia, were triggered by sighs in 11 of 11 patients with sickle cell and 8 of 11 control subjects. Although the sigh frequency was the same in both groups, the probability of a sigh inducing a perfusion drop was 78% in patients with sickle cell and 17% in control subjects (P < 0.001). Evidence for sigh-induced sympathetic nervous system dominance was seen in patients with sickle cell (P < 0.05), but was not significant in control subjects.

CONCLUSIONS

These data demonstrate significant disruption of autonomic nervous system balance, with marked parasympathetic withdrawal in response to transient hypoxia. They draw attention to an enhanced autonomic nervous system–mediated sigh–vasoconstrictor response in patients with sickle cell that could increase red cell retention in the microvasculature, promoting vasoocclusion.

Autonomic nervous system reactivity: children with and without sickle cell disease

BACKGROUND

Previous studies of healthy children have indicated a link between autonomic nervous system (ANS) reactivity and health outcomes, but there is limited research on whether ANS reactivity is similar for children with chronic conditions.

OBJECTIVE

The aim of this study was to determine if ANS reactivity differs for children with sickle cell disease (SCD) compared with a community sample of children without SCD.

METHOD

In two cross-sectional, descriptive studies, 32 public school children without chronic health problems were compared with 33 children with SCD. The children were 5-8 years old and they completed standardized protocols measuring ANS responses (respiratory sinus arrhythmia and preejection period) during rest and challenge conditions in social, cognitive, sensory, and emotion domains. Reactivity was calculated as the difference between challenge response minus rest for each domain and overall.

RESULTS

There were differences in the distributions of the samples in parent education and child age, so these variables were adjusted for in subsequent analyses. The community sample showed parasympathetic withdrawal (low respiratory sinus arrhythmia scores) and greater parasympathetic reactivity (low respiratory sinus arrhythmia difference scores and percentage of negative scores) compared with the children with SCD in the social (p < .05) and sensory (p < .05) domains. The children with SCD showed greater sympathetic reactivity (low preejection period difference scores) compared with the community children in the cognitive domain (p < .05), and a greater percentage of children with SCD versus the community children showed negative preejection period difference scores (sympathetic reactivity) in the social domain (p < .05). The community sample, but not the children with SCD, showed changes in respiratory sinus arrhythmia across domains (p < .05).

DISCUSSION

Children with SCD may display a different pattern of ANS responses to laboratory challenges compared with children without SCD from the same community.

Frequency of pain crises in sickle cell anemia and its relationship with the sympatho-vagal balance, blood viscosity and inflammation

BACKGROUND

Recent evidence suggests that autonomic nervous system activity could be involved in the pathophysiology of sickle cell disease, but it is unclear whether differences in autonomic nervous system activity are detectable during steady state in patients with mild and severe disease. The aim of the present study was to compare the autonomic nervous system activity, blood rheology, and inflammation in patients with sickle cell anemia according to the frequency of acute pain crisis.

DESIGN AND METHODS

Twenty-four healthy volunteers, 20 patients with sickle cell anemia with milder disease, and 15 patients with sickle cell anemia with more severe disease were recruited. Milder disease was defined as having no pain crisis within the previous year. More severe disease was defined as having had within the previous year three or more pain crises which were documented by a physician and required treatment with narcotics. The autonomic nervous system activity was determined by spectral analysis of nocturnal heart rate variability. Blood viscosity determination and measurements of several inflammatory markers (interleukin-6, soluble vascular cell adhesion molecule-1, soluble CD40 ligand and sL-selectin) were made on blood samples collected in steady-state conditions.

RESULTS

Results showed that: 1) patients who had suffered more frequent pain crises had lower parasympathetic activity and greater sympatho-vagal imbalance than both controls and patients with milder disease. However, when adjusted for age, no significant difference was detected between the two sickle cell anemia patient groups; 2) patients who had suffered more frequent pain crises had higher blood viscosity than patients with milder disease, and this was not dependent on age.

CONCLUSIONS

Results from the present study indicate that both the autonomic nervous system activity and blood viscosity are impaired in patients with sickle cell anemia exhibiting high frequency of pain crisis in comparison with those who did not experience a crisis within the previous year.

Development and validation of a pediatric severity index for sickle cell patients

There is no instrument to measure severity of sickle cell disease (SCD) in pediatric patients that is generally accepted. The aim of this study was to develop and validate a severity index for SCD in children. We developed an index consisting of 12 items and tested its validity of the index using data from 92 children. We tested whether different scores were obtained for patients classified by severity both subjectively and objectively by a partially validated existing index. Furthermore, we tested whether the index could differentiate patients classified according to genotype or the number of α-gene deletions and evaluated whether the score on the index was correlated with the average number and days of hospitalizations/year, age and a risk of death score. We explored the effect of three different weighting systems (Score A, B, and C) to summarize these items. All weightings demonstrated a significant difference between the scores of mild, moderate, and severely affected patients, as classified by a subjective rating or with an existing index (P < 0.01). The index clearly differentiated patients by genotype (P < 0.01) or α-gene deletions (P < 0.01). The correlation with hospitalization was moderate. Age and the risk of death score were weakly associated with the pediatric severity index for SCD. This is the first pediatric SCD severity index that was developed and validated using modern clinimetric methodology. The validity and reliability of this index should be further evaluated in a prospective study including a larger cohort, preferably diagnosed at birth.

Sickle cell disease: selected aspects of pathophysiology

Sickle cell disease (SCD), a genetically-determined pathology due to an amino acid substitution (i.e., valine for glutamic acid) on the beta-chain of hemoglobin, is characterized by abnormal blood rheology and periods of painful vascular occlusive crises. Sickle cell trait (SCT) is a typically benign variant in which only one beta chain is affected by the mutation. Although both SCD and SCT have been the subject of numerous studies, information related to neurological function and transfusion therapy is still incomplete: an overview of these areas is presented. An initial section provides pertinent background information on the pathology and clinical significance of these diseases. The roles of three factors in the clinical manifestations of the diseases are then discussed: hypoxia, autonomic nervous system regulation and blood rheology. The possibility of a causal relationship between these three factors and sudden death is also examined. It is concluded that further studies in these specific areas are warranted. It is anticipated that the outcome of such research is likely to provide valuable insights into the pathophysiology of SCD and SCT and will lead to improved clinical management and enhanced quality of life.

Stress reactivity as a moderator of family stress, physical and mental health, and functional impairment for children with sickle cell disease

OBJECTIVE

To evaluate whether autonomic nervous system (ANS) reactivity modifies the relation between family stress, and physical and mental health, and functional impairment for children with sickle cell disease.

METHODS

Thirty-eight 5-to 8-year old children with sickle cell disease completed a 20-minute ANS reactivity protocol measuring respiratory sinus arrhythmia and pre-ejection period during comparison and challenge tasks in social, cognitive, sensory, and emotion domains. Domain-specific reactivity was calculated as the difference between challenge and comparison tasks; overall reactivity was calculated across domains as the mean of the difference scores. ANS profile scores combined the overall respiratory sinus arrhythmia and pre-ejection period reactivity scores. Caregivers completed measures of family stress, child physical and mental health symptoms, and functional impairment.

RESULTS

Family stress was associated with child functional impairment whereas overall and cognitive ANS reactivity was associated with co-morbid internalizing and externalizing mental health symptoms. Interaction models showed that children with the classic ANS profile (parasympathetic inhibition and sympathetic activation) in the cognitive and emotion domains were most vulnerable to the effects of stress, with more functional impairment and injuries when family stress was high, controlling for age, sex, and parent education.

CONCLUSION

The costs to patients and families in diminished quality of life and to the health care system could be reduced by further exploration of strategies to identify children with sickle cell disease who are most vulnerable under conditions of high family stress and heightened psychobiologic reactivity.

Prolonged QTc interval in children and young adults with sickle cell disease at steady state

BACKGROUND

Prolongation of the QTc interval may be more common than previously believed among individuals with sickle cell disease (SCD). The clinical associations and natural history of QTc prolongation remain unclear in this population. Our objectives were to determine the prevalence of prolonged QTc and evaluate its relationship to clinical factors in children and young adults with SCD.

PROCEDURES

We analyzed data from subjects 10 to 25 years old with SCD enrolled in our pulmonary hypertension screening protocol. Screening included echocardiography (ECHO), 12-lead electrocardiogram (ECG) and laboratory testing at steady state. QTc interval >440 msec was considered prolonged.

RESULTS

ECG data from 76 subjects (57% male, mean age 14.2 +/- 3 years old, range 10-24) were analyzed. We observed prolonged QTc in 29/76 (38%) subjects. Despite evidence of left ventricular hypertrophy (LVH) in 50/76 (66%) subjects, the frequency of LVH was not significantly different in subjects with and without QTc prolongation. When compared to subjects with normal QTc, subjects with prolonged QTc had higher mean tricuspid regurgitant jet velocity (2.51 +/- 0.27 m/sec vs. 2.33 +/- 0.26 m/sec, P = 0.010) as well as higher mean lactate dehydrogenase (433 +/- 142 IU/L vs. 343 +/- 142 IU/L, P = 0.000) and aspartate aminotransferase (48 +/- 20 IU/L vs. 39 +/- 15 IU/L, P = 0.026). A larger proportion of subjects with prolonged QTc also had a history of recurrent acute chest syndrome (66% vs. 38%, P = 0.038).

CONCLUSIONS

We conclude that QTc prolongation is a frequent finding in SCD not associated with LVH. Elevated pulmonary pressures, hemolysis and acute chest syndrome may represent risk factors for prolonged QTc in this population.

Abnormal cardiac autonomic control in sickle cell disease following transient hypoxia

Abnormalities in autonomic control in sickle cell anemia (SCA) patients have been reported by multiple researchers. However their potential causal association with sickle cell crisis remains unknown. We employed hypoxia, a known trigger to sickle cell crisis, to perturb the autonomic systems of the subjects. Cardiac autonomic control was non-invasively assessed by tracking the changes in heart rate variability (HRV) that occur following brief exposure to a hypoxia stimulus. Time varying spectral analysis of HRV was applied to estimate the cardiac autonomic response to the transient episode of hypoxia. The results demonstrate that cardiovascular autonomic response to hypoxia is substantially more sensitive in SCA than in normal controls. We also developed a model to compensate for the confounding effects of respiration on the HRV spectral indices by using the corresponding respiration signal to compensate for the respiratory correlated part of the HRV. This technique improved the resolution with which the effect of hypoxia on changes in HRV could be measured.

Psychological status of patients with mucopolysaccharidosis type II and their parents

BACKGROUND

The aim of the present study was to delineate the psychological status of 10 patients with the attenuated phenotype of mucopolysaccharidosis type II (MPS-II) and their parents (six fathers and five mothers) for the improvement of clinical management.

METHODS

Intellectual ability was evaluated using the Wechsler Intelligence Scale. Activities of daily living (ADL) was assessed using the Functional Independence Measure. The personality and psychiatric aspects were analyzed using the Yatabe-Guilford Personality test (Y-G test) and the Tree-Drawing Test. Mental health was assessed using the General Health Questionnaire 60 (GHQ-60) and State-Trait Anxiety Inventory (STAI).

RESULTS

Intellectual background, measured with full-scale, verbal and performance IQ, were 72.8, 76.1 and 79.3, respectively. Nine of 10 patients were not judged as having neurosis and a psychotic tendency with the Y-G test. In the tree-drawing test, many patients drew a tree without ground, suggesting that they have difficulties in making relationships with surrounding people and the community. The child patient with a psychosis pattern on the Y-G test, drew a bizarre tree, suggesting psychological problems. GHQ-60 and STAI survey indicated that the patients and their parents had higher levels of anxiety. A significant negative correlation between GHQ-60 score and ADL (R = -0.77) was identified, suggesting that the psychological status may worsen as ADL decreases.

CONCLUSIONS

Patients with MPS-II and their parents had higher risks for mental problems. Understanding psychological status is essential when providing genetic counseling or therapeutic intervention.

Abnormal autonomic cardiac response to transient hypoxia in sickle cell anemia

The objective of this study was to non-invasively assess cardiac autonomic control in subjects with sickle cell anemia (SCA) by tracking the changes in heart rate variability (HRV) that occur following brief exposure to a hypoxic stimulus. Five African-American SCA patients and seven healthy control subjects were recruited to participate in this study. Each subject was exposed to a controlled hypoxic stimulus consisting of five breaths of nitrogen. Time-varying spectral analysis of HRV was applied to estimate the cardiac autonomic response to the transient episode of hypoxia. The confounding effects of changes in respiration on the HRV spectral indices were reduced by using a computational model. A significant decrease in the parameters related to parasympathetic control was detected in the post-hypoxic responses of the SCA subjects relative to normal controls. The spectral index related to sympathetic activity, on the other hand, showed a tendency to increase the following hypoxic stimulation, but the change was not significant. This study suggests that there is some degree of cardiovascular autonomic dysfunction in SCA that is revealed by the response to transient hypoxia.

Neurobehavioral impact of sickle cell disease in early childhood

The physical effects of sickle cell disease (SCD) begin in infancy or early childhood, yet most behavioral studies have focused on school-age children. We evaluated the impact of higher versus lower neurologic risk on language, motor abilities, executive functions, and temperament in toddlers and early preschoolers with SCD. Thirty-nine children with higher risk SCD were compared to 22 children with lower risk SCD. Language and motor abilities were lower in older compared with younger children but were unrelated to sickle cell subgroups. Executive functions, particularly working memory, were poorer in children with higher risk SCD regardless of age. Parent-reported activity level was also lower in children with higher risk. Specific behavioral influences of SCD are evident early in childhood and include working memory decrements. Executive function deficits in SCD can emerge early in life and may be an important context for other areas of cognitive and behavioral development.

Increased QT dispersion in sickle cell disease: effect of pulmonary hypertension

BACKGROUND

QT dispersion has been proposed to be a predictor of adverse outcomes in a variety of cardiac disease states. The objective of this study was to examine QT dispersion in patients with sickle cell disease (SCD) and to assess the effect of pulmonary hypertension (PHT) on QT dispersion.

METHODS

We performed Doppler echocardiographic assessments of pulmonary artery systolic pressure in 73 (mean age 18.5 +/- 8.0 years) steady-state SCD patients and 25 (mean age 19.6 +/- 7.2 years) healthy subjects. Resting 12-lead electrocardiogram was recorded and QT dispersion was calculated as the difference between maximum and minimum QT intervals. Bazett's formula was used to obtain a rate-corrected value of the QT interval (QTc).

RESULTS

Maximum QTc, minimum QTc and QTc dispersion were significantly increased in SCD patients compared to the control subjects (p < 0.0001, p < 0.05, p < 0.0001, respectively). Among SCD patients, patients with PHT had higher maximum QTc and QTc dispersion than patients without PHT (p < 0.0001). However, minimum QTc showed no significant differences between the two patient groups.

CONCLUSION

QTc dispersion is significantly increased in SCD patients, especially those with PHT indicating regional inhomogeneity of ventricular repolarization.