Consequences of paediatric sleep disordered breathing: contributions from Australian and New Zealand investigators

Sleep Apnea Specific Hypoxic Burden in Children With Down Syndrome and Typically Developing Children

Hypoxic burden (HB) is a measure incorporating frequency, depth and duration of respiratory event-related desaturations. While HB is associated with cardiovascular disease in adults with obstructive sleep apnea (OSA), it has not been assessed in typically developing (TD) children with OSA, nor in children with Down syndrome (DS), who have a higher incidence of OSA with more severe hypoxia. We assessed whether HB in these children was related to heart rate variability (HRV), an indicator of cardiovascular outcomes. Children (3-19 years, n = 44) with DS and TD children matched for OSA severity, age and sex underwent overnight polysomnography and were grouped into primary snoring (PS), Mild or Moderate/Severe (MS) OSA. HRV was analysed using power spectral analysis of the electrocardiograph. Regression analysis determined whether HB was predictive of HRV. Children with MS OSA in both groups had higher HB compared with children with PS (p < 0.001 for both) and Mild OSA (DS, p < 0.001; TD, p < 0.05). Children with DS and PS or Mild OSA had higher HB compared with TD children (PS p < 0.05; Mild OSA p < 0.001). There was no difference between the MS OSA groups. HB predicted dampened sympathetic and parasympathetic activity only in children with DS (R2 = 0.12, β = -10.6, SE = 4.6, p = 0.03). HB was higher in children with DS and PS or Mild OSA compared to TD children and predicted dampened autonomic function in children with DS. The potential contribution of the adverse effects of HB on autonomic function adds weight to the importance of identifying and treating OSA in children with DS.

Sleep disturbances in children and adolescents after kidney transplantation

BACKGROUND

Disturbances of sleep are prevalent among children with chronic kidney disease. However, the aetiology of sleep disorders in children particularly after kidney transplantation is not clear. We sought to ascertain the prevalence and type of sleep disturbances in paediatric kidney transplant recipients and to identify predictors of sleep disturbances in this population.

METHODS

Caregivers of kidney transplant recipients completed online questionnaires about their child's sleep. The questionnaires utilised were the Sleep Disturbance Scale for Children (SDSC), the Epworth Sleepiness Scale for Children and Adolescents (ESS-CHAD), questions about sleep hygiene, and questions about restless leg syndrome. Demographic and clinical details were collected from medical records.

RESULTS

Thirty-five children were included in the study, with a median (IQR) age of 14.1 years (9.5-16.1) and median years (IQR) since transplant of 3.7 (0.7-8.7) years, and 72.0% were identified to have at least one category of sleep disturbance according to scores on the SDSC. The most common sleep disturbances reported were disorders of initiating and maintaining sleep (DIMS) (40.0%) and disorders of excessive somnolence (DOES) (31.4%). Statistically significant predictors of sleep disturbances include low estimated glomerular filtration rate and increased age. Among children who screened positive for DIMS and DOES, the majority indicated use of electronic devices in 1 h before bed.

CONCLUSIONS

A high prevalence of sleep disturbances has been identified in children after kidney transplants, and some risk factors may be modifiable. Further studies are required to understand whether there are other readily modifiable predictors of sleep disturbances.

Analysis of QRS complex morphology in children and adolescents with obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) leads to many cardiovascular, neurologic, metabolic, and neurocognitive consequences. Conduction deficits, deviations in electrical axis, and changes in QRS morphology reflect the impairments in cardiac muscle activity and underlie the cardiovascular complications of OSAS. Here we aimed to determine the relationship between OSAS and changes in the cardiac conduction system in children and adolescents. During the 6-month duration of the study, all children having the diagnosis of OSAS in Sleep and Disorders Unit following a full-night polysomnography (PSG) were consecutively evaluated. ECGs were performed and analyzed in the Division of Pediatric Cardiology, Department of Pediatrics. The maximum spatial vector size (QRSmax), QRS electrical axis (EA), left and right ventricular hypertrophy, and the presence of fragmented QRS (fQRS) or prolonged R or S wave were examined in detail. A total of 17 boys with OSAS and 13 healthy boys participated in the study. The mean QRSmax and the QRSmax on V5 derivative were significantly lower in the patient group compared to those in the control group (p = 0.011 and p = 0.017, respectively). EA was similar between the two groups. While none of the patients with OSAS nor the control group had left ventricular hypertrophy, only one boy with OSAS had right ventricular hypertrophy according to ECG-derived analysis. The percentage of fQRS or notched R or S waves was significantly higher in patients with OSAS compared to healthy controls (p = 0.035), especially in children below the age of 5 years (p = 0.036).  Conclusion: This study demonstrated that male children and adolescents with OSAS have a combination of QRS complex changes characterized by low QRS voltages, and increased frequency of fragmented QRS. These findings reflect that the electrical remodeling and structural remodeling of the myocardium are considerably affected by OSAS in children and adolescents, leading to ventricular changes and intraventricular conduction problems. What is Known: • Pediatric obstructive sleep apnea syndrome (OSAS) characterized by recurrent intermittent hypoxemia, hypercapnia, and sleep fragmentation results in sympathetic nervous system activation, increased inflammation, and hypoxic endothelial dysfunction. When left untreated, OSAS leads to many cardiovascular, neurologic, metabolic and neurocognitive consequences, and also to sudden infant death syndrome in young children, probably due to the involvement of the cardiac conduction system. What is New: • This study demonstrated that mean QRSmax was significantly lower in male children and adolescents with OSAS, reflecting the structural and electrical remodeling of the myocardium, and one boy with OSAS had RVH according to ECG-derived analysis. The percentage of fQRS or notched R or S waves was much higher in boys with OSAS, especially in children below the age of five years. These finding showed that myocardium was considerably affected to impair the intraventricular conduction in younger children with OSAS.

Down syndrome and the autonomic nervous system, an educational review for the anesthesiologist

Approximately one in every 700 babies in the United States is born with Down syndrome, or 0.14%. Children with Down syndrome have cognitive impairment and congenital malformations necessitating frequent occurrences of general anesthesia and surgery. The thoughtful perioperative care of children with Down syndrome is relevant and acutely complex for the pediatric anesthesiologist. Behavior, sedation, hypotonia, upper airway obstruction, venous access, and bradycardia are omnipresent concerns apart from the surgical pathology. Down syndrome is also associated with autonomic nervous system dysfunction, a comorbidity that is overlooked in discussions of perioperative care and is described thus far in adults. Autonomic nervous system function or dysfunction may explain the phenotypical features of the perioperative challenges listed above. For this reason, understanding the development and measurement of autonomic nervous system function is important for the pediatric anesthesiologist. Definition and quantification of sympathetic and parasympathetic function will be reviewed.

Cell-Selective Altered Cargo Properties of Extracellular Vesicles Following In Vitro Exposures to Intermittent Hypoxia

Intermittent hypoxia (IH), a hallmark of obstructive sleep apnea (OSA), is associated with cardiovascular and metabolic dysfunction. However, the mechanisms underlying these morbidities remain poorly delineated. Extracellular vesicles (EVs) mediate intercellular communications, play pivotal roles in a multitude of physiological and pathological processes, and could mediate IH-induced cellular effects. Here, the effects of IH on human primary cells and the release of EVs were examined. Microvascular endothelial cells (HMVEC-d), THP1 monocytes, THP1 macrophages M0, THP1 macrophages M1, THP1 macrophages M2, pre-adipocytes, and differentiated adipocytes (HAd) were exposed to either room air (RA) or IH for 24 h. Secreted EVs were isolated and characterized using transmission electron microscopy, nanoparticle tracking analysis, and Western blotting. The effects of each of the cell-derived EVs on endothelial cell (EC) monolayer barrier integrity, on naïve THP1 macrophage polarity, and on adipocyte insulin sensitivity were also evaluated. IH did not alter EVs cell quantal release, but IH-EVs derived from HMVEC-d (p < 0.01), THP1 M0 (p < 0.01) and HAd (p < 0.05) significantly disrupted HMVEC-d monolayer integrity, particularly after H₂O₂ pre-conditioning. IH-EVs from HMVEC-d and THP1 M0 elicited M2-polarity changes did not alter insulin sensitivity responses. IH induces cell-selective changes in EVs cargo, which primarily seem to target the emergence of endothelial dysfunction. Thus, changes in EVs cargo from selected cell sources in vivo may play causal roles in some of the adverse outcomes associated with OSA.