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Conclusions: Measurements of urinary albumin, total protein, and albumin-to-creatinine ratio are minimally affected by storage at ؊70°C for approximately 2.5 yr. Prolonged storage results in small decreases of urinary albumin and protein that do not substantially affect phenotype classification of overt renal disease.

Oxidative stress plays an essential role in processes of signaling and damage to biomolecules during early perinatal life. Isoprostanoids and isofuranoids from the free radical-catalyzed peroxidation of polyunsaturated fatty acids (PUFAs) are widely recognized as reliable biomarkers of oxidative stress. However, their quantification is not straightforward due to high structural similarity of the compounds formed. In this work, a semi-quantitative method for the analysis of adrenic acid (AdA, C22:4 n-6) non-enzymatic peroxidation products (i.e. dihomo-isoprostanes and dihomo-isofurans) was developed. The proposed ultra-performance liquid chromatography - tandem mass spectrometry (UPLC-MS/MS) method was applied to the analysis of blood plasma and urine from preterm infants providing information about AdA peroxidation.

<b><i>Introduction:</i></b> Lipid peroxidation products are present following oxidation of polyunsaturated fatty acids in the eye, brain, and various cell membranes. Elevated levels of lipid peroxidation products and increased intermittent hypoxemia (IH) events have been associated with adverse outcomes in extremely preterm infants. The moderate preterm newborn has a still-developing oxidant defense system and immature respiratory control, but little is known about lipid peroxidation levels and IH in this larger and more common preterm population. <b><i>Objective:</i></b> To determine the association between oxidative stress and IH in moderate preterm infants. <b><i>Method:</i></b> Oxygen saturation was continuously monitored in 51 moderate preterm infants (i.e., 31 + 0/7 to 33 + 6/7 weeks’ gestation). Urine samples were collected at the end of the first and second weeks of life. Samples were analyzed for total lipid peroxidation products (neurofurans, isofurans, neuroprostanes, isoprostanes, and di-homo-isofurans). <b><i>Result:</i></b> At week 1, there was a correlation between increased IH frequency and neurofurans (<i>p</i> &#x3c; 0.04) and di-homo-isofurans (<i>p</i> &#x3c; 0.003). At week 2, there was no correlation between IH and lipid peroxidation markers. Ele­vations in neurofurans, isofurans, neuroprostanes, and di-homo-isofurans in the first and/or second week of life were associated with a longer stay in hospital. <b><i>Conclusion:</i></b> Elevations in lipid peroxidation biomarkers in moderate preterm infants during their first weeks of life are associated with a higher frequency of IH and prolonged hospitalization.

Intermittent hypoxaemia (IH) events are well described in extremely preterm infants, but the occurrence of IH patterns in more mature preterm infants remains unclear. The objective of this study was to characterise the effect of gestational age on early postnatal patterns of IH in extremely (<28 weeks), very (28–<32 weeks) and moderately (32–<34 weeks) preterm infants. As expected, extremely preterm infants had a significantly higher frequency of IH events of longer durations and greater time with hypoxaemia versus very and moderately preterm infants. In addition, the postnatal decrease in IH duration was comparable in the very and moderately preterm infants. This progression of IH events should assist clinicians and families in managing expectations for resolution of IH events during early postnatal life.