Vasiliki Varlami

Effects of adenotonsillectomy on R-R interval and brain natriuretic peptide levels in children with sleep apnea: A preliminary report

OBJECTIVES Obstructive sleep apnea is associated with decreased R-R interval length and overall R-R interval variability in the electrocardiogram along with increased morning brain natriuretic peptide (BNP) blood levels. These findings indicate enhanced sympathetic tone and cardiac strain. In this study, it was hypothesized that adenotonsillectomy (AT) in children with sleep apnea is accompanied by improvement in polysomnography indices, increase in length and variability of R-R interval, and reduction in BNP levels. METHODS Polysomnography and measurements of morning BNP levels were performed before and 4-6months after AT. Mean and standard deviation of R-R interval were calculated from polysomnography electrocardiogram recordings. RESULTS Twenty-one children were studied. Apnea-hypopnea index and log-transformed BNP levels decreased postoperatively from 8.4±7.6 episodes/h and 2.2±0.7, to 1.8±1.4 episodes/h and 1.9±0.3, respectively (p<0.05). Mean R-R interval increased from 703.2±137.4ms (Stage 2), 699.3±135.8ms (Stage 3), 707.4±128.9ms (Stage 4) and 660.5±140.1ms (Stage REM), to 773.5±122.7ms (Stage 2), 765.7±73.7ms (Stage 3), 771.2±71.6ms (Stage 4), and 738.6±81.7ms (Stage REM), respectively (p<0.05 for comparisons pre- vs. post-operatively). Standard deviation of R-R in Stage 2 increased from 88.5±29.6 to 122.7±67ms (p=0.045). CONCLUSIONS Increase in nocturnal length of R-R interval and decrease in BNP levels after AT for sleep apnea may reflect postoperative reduction in sympathetic tone and cardiac strain.

Nocturnal enuresis is associated with moderate-to-severe obstructive sleep apnea in children with snoring

Background:Conflicting data suggest that prevalence of monosymptomatic primary nocturnal enuresis (NE) increases with increasing severity of obstructive sleep apnea (OSA) in childhood and especially in girls. We hypothesized that NE is associated with increased risk of moderate-to-severe OSA (obstructive apnea-hypopnea index (AHI) >5 episodes/hour) among children with snoring.Methods:Data of children (≥5 y old) with snoring who were referred for polysomnography over 12 y were reviewed.Results:Data of 525 children with mean age (±SD) 7.5 (± 2.2) y and median obstructive AHI (10th-90th percentiles) 1.9 (0.4–7.3) episodes/hour were analyzed. Three hundred and fifty-five children (67.6%) had NE and 87 (16.6%) had moderate-to-severe OSA. There was no interaction between NE and gender regarding the association with moderate-to-severe OSA (P > 0.05). NE was associated significantly with presence of moderate-to-severe OSA after adjustment for tonsillar hypertrophy, obesity, gender, and age (adjusted odds ratio = 1.92 (1.08–3.43); P = 0.03). Presence of NE had high sensitivity (78.2%) and low positive predictive value (19.2%) for detecting moderate-to-severe OSA and low specificity (34.5%) and high negative predictive value (88.8%) for ruling it out.Conclusion:Children with snoring and without NE referred for polysomnography are less likely to have moderate-to-severe OSA compared to those with NE.

Uric acid excretion in North American and Southeast European children with obstructive sleep apnea.

BACKGROUND AND OBJECTIVES Responses to nocturnal hypoxemia accompanying sleep-disordered breathing (SDB) may vary in different populations. Aims of this study were to (1) assess whether severity of SDB is related to uric acid excretion in North American and Southeast European children and (2) evaluate the interaction between nocturnal hypoxemia and country of childrens origin in uric acid excretion. METHODS Consecutive US and Greek children with snoring who were referred for polysomnography were recruited. Uric acid excretion expressed as uric acid-to-creatinine concentrations ratio in a morning urine specimen was the primary outcome measure. RESULTS One hundred and twenty-six US children (6.8+/-0.7years old) and 123 Greek children (6.4+/-2.5years old) were recruited. Forty-three US and 53 Greek participants had moderate-to-severe nocturnal hypoxemia (SpO(2) nadir <90%). Obstructive apnea-hypopnea index and SpO(2) nadir were related to uric acid excretion in Greek (but not US) children after adjustment by age, gender and body mass index z-score (p<0.05). There was a significant interaction between severity of hypoxemia and country of childrens origin in uric acid excretion after adjustment by age, gender and body mass index z-score (p=0.036). Greek children with moderate-to-severe hypoxemia had higher uric acid excretion (0.85+/-0.35) than those with mild/no hypoxemia (0.69+/-0.25) (p=0.005). US children with moderate-to-severe hypoxemia (0.41+/-0.20) did not differ in uric acid excretion from those with mild/no hypoxemia (0.42+/-0.22) (p=0.823). CONCLUSIONS Uric acid excretion differs in children with SDB and different ethnic backgrounds or environmental exposures.

Low-grade albuminuria in children with obstructive sleep apnea

Small urinary protein loss (low‐grade albuminuria or microalbuminuria) may reflect altered permeability of the glomerular filtration barrier. In the present study, it was hypothesized that children with obstructive sleep apnea have an increased risk of microalbuminuria compared with control subjects without sleep‐disordered breathing. Albumin‐to‐creatinine ratio was measured in morning spot urine specimens collected from consecutive children with or without snoring who were referred for polysomnography. Three groups were studied: (i) control subjects (no snoring, apnea–hypopnea index < 1 episode h−1; n = 31); (ii) mild obstructive sleep apnea (snoring, apnea–hypopnea index = 1–5 episodes h−1; n = 71); and (iii) moderate‐to‐severe obstructive sleep apnea (snoring, apnea–hypopnea index > 5 episodes∙h−1; n = 27). Indications for polysomnography in control subjects included nightmares, somnambulism and morning headaches. An albumin‐to‐creatinine ratio > median value in the control group (1.85 mg of albumin per g of creatinine) was defined as elevated. Logistic regression analysis revealed that children with moderate‐to‐severe obstructive sleep apnea, but not those with mild obstructive sleep apnea, had increased risk of elevated albumin‐to‐creatinine ratio relative to controls (reference) after adjustment for age, gender and presence of obesity: odds ratio 3.8 (95% confidence interval 1.1–12.6); P = 0.04 and 1.5 (0.6–3.7); P > 0.05, respectively. Oxygen desaturation of hemoglobin and respiratory arousal indices were significant predictors of albumin‐to‐creatinine ratio (r = 0.31, P = 0.01; and r = 0.43, P < 0.01, respectively). In conclusion, children with moderate‐to‐severe obstructive sleep apnea are at significantly higher risk of increased low‐grade excretion of albumin in the morning urine as compared with control subjects without obstructive sleep apnea. These findings may reflect altered permeability of the glomerular filtration barrier related to nocturnal hypoxemia and sympathetic activation which are induced by obstructive sleep apnea.

Correlation of urinary excretion of sodium with severity of sleep-disordered breathing in children: A preliminary study†

Nocturnal urinary sodium excretion is related to blood pressure (BP) levels. Elevated BP and increased nocturnal natriuresis have been demonstrated in adults with sleep apnea. Although evidence indicates increased BP in children with obstructive sleep‐disordered breathing (SDB), it is unknown whether these children have also enhanced urinary sodium excretion.