Can sleep disordered breathing result in metabolic abnormalities?

Can sleep disordered breathing result in metabolic abnormalities?

Cranial ultrasounds: Are they reliable? Most newborn intensive care unit centers perform serial cranial ultrasound evaluations early in the course of ...

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Cranial ultrasounds: Are they reliable? Most newborn intensive care unit centers perform serial cranial ultrasound evaluations early in the course of hospitalization for premature infants and often a follow-up examination is done at 4-6 weeks of age. These evaluations are done to document the presence of intracranial hemorrhage, to guide choice of therapies that may exacerbate risk of further hemorrhage, and to counsel families about neurodevelopmental outcomes. These data are also often used for benchmark comparisons. There have been few studies that investigated the reliability or accuracy of these findings, and yet randomized controlled trials in neonatal patients and interventional studies frequently include presence and degree of intraventricular hemorrhage (IVH) in their outcome data. Hintz et al describe the interobserver reliability and accuracy of the interpretation of cranial ultrasounds in premature infants. The authors took advantage of a large collection of ultrasound examinations performed as part of the NICHD Neonatal Network’s trial on the safety of inhaled nitric oxide. This was an important outcome variable because early case reports had suggested a potential risk of IVH; however, the trial found no differences in the rates of severe IVH or periventricular leukomalacia (PVL) between treated infants and controls. Scans were read by central readers who were board-certified radiologists and employed a structured data instrument. The study demonstrated a high degree of agreement between “local readers” and the central “experts.” This agreement was best for Grades 3 and 4 IVH, less so for periventricular leukomalacia, and poor for milder degrees of IVH. These observations are reassuring but also raise a note of caution. There is a strong association between severe degrees of IVH and poor neurodevelopmental outcome. The strength of those associations is less for milder degrees of bleeding. Given the differences in interpretation between the experts and the home-based readers for milder degrees of IVH, care should be exercised by clinicians in counseling families regarding the association between cranial ultrasound findings and neurodevelopmental prognosis. The study also raises a note of caution for investigators who use cranial ultrasound findings as a study outcome. Future designs should employ strategies to confirm the reliability of the ultrasound findings. Likewise, additional data of this kind on interobserver reliability of intracranial pathology from computerized tomography or MRI evaluations is needed. All that said, our understanding of the reliability of cranial ultrasound examinations is advanced by this report. —James Padbury, MD page 592

The Journal of Pediatrics

Can sleep disordered breathing result in metabolic abnormalities? It is well known that obesity, and in particular central obesity, in adults is related to the development of the metabolic syndrome, a constellation of factors, including insulin resistance, dyslipidemia, and hypertension, which is associated with increased risk of diabetes and cardiovascular disease. Recent studies have also implicated sleep disordered breathing as part of these interrelationships. There has not been extensive research in this area for pediatric patients. In this issue of The Journal, Verhulst et al assessed whether sleep disordered breathing is a risk factor for the metabolic syndrome in overweight children and adolescents. They found that indicators of sleep disordered breathing were independent predictors of the metabolic syndrome. They also showed that, after controlling for obesity, sleep variables were associated with low HDL-cholesterol, higher triglycerides, and elevated glucose levels during an oral glucose tolerance test. These results support the concept that these variables are interrelated in children as well as adults. It may be beneficial to diagnose and treat sleep disordered breathing in overweight children in an effort to prevent future cardiovascular disease. —Stephen R. Daniels, MD, PhD page 608

Pharmacologic approach to PKU? We often look at the inborn errors of metabolism such as phenylketonuria (PKU) as “single gene disorders,” assuming that their phenotypes are fairly consistent. A small study by Blau and Fiege in the current issue of The Journal reminds us that this is not always the case. These workers have expanded on some existing information, which has suggested that there is a subset of patients with PKU in whom treatment with 6R-tetrahydrobiopterin (BH4) can lower blood phenylalanine levels. The study is a very technical one, and BH4 is not widely available at this point. Nonetheless, this work suggests that there may well come a time when some children with PKU may be managed with drug therapy or a combination of drug therapy and dietary intervention. —Thomas R. Welch, MD page 627

June 2007

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