Oxidative Stress in Preterm Neonates at Birth and on the Seventh Day of Life

Abstract

Previous studies have demonstrated increased oxidative damage to proteins and increased lipid peroxidation products in the plasma of hypoxic newborns at birth. We tested the hypothesis that hypoxic preterm newborns are at increased risk for oxidative stress in the first week of life. Heparinized blood samples of 34 hypoxic and 15 control preterm newborns were obtained at birth from the umbilical vein immediately after delivery and from a peripheral vein on postnatal d 7. Plasma levels of hypoxanthine, total hydroperoxide (TH), and advanced oxidation protein products (AOPP) were measured in cord blood and blood drawn on d 7. Hypoxanthine, TH, and AOPP levels were significantly higher in cord and d 7 blood samples of hypoxic newborn than control infants. Statistically significant correlations were observed between AOPP and hypoxanthine and between AOPP and TH plasma levels on d 7. AOPP and TH plasma levels significantly increased from cord to d 7 blood in neonates without hypoxia. These findings show that the oxidative stress observed in cord blood of hypoxic preterm newborns is still higher than control infants on d 7. The significant increase in TH and AOPP levels in nonhypoxic preterm newborns at the end of the first postnatal week indicates that damage caused by free radicals also occurs in nonhypoxic babies with normal clinical course. In summary, TH and AOPP production is prolonged for several days after birth in hypoxic preterm babies. The risk of free radical damage is lower but still exists in preterm neonates with normal clinical course. Perinatal hypoxic-ischemic injury is an important cause of neonatal morbidity. Numerous experimental studies have demonstrated FR production and oxidative damage caused by hypoxia in fetal life (1-3). Although the clinical consequences of hypoxia are readily observed, the specific biochemical processes preceding the onset of FR damage are not well understood. Oxidative stress exists and tissue damage is possible when there are low levels of antioxidants or increased FR activity (4). Newborns and particularly preterm infants are at high risk for oxidative stress and are very susceptible to oxidative damage by FR (5). Indeed, there is evidence of an imbalance between antioxidant and oxidant-generating systems, which causes oxidative damage (6). Birth is an oxidative challenge for the newborn. The sharp postnatal transition from the relatively low oxygen intrauterine environment to the significantly higher oxygen extrauterine environment exposes the newborn to FR. The increase in FR generation is exacerbated by the low efficiency of natural antioxidant systems in the newborn, especially if preterm, predisposing it to oxidative damage (7). High FR generation and protein oxidation products have been detected in the plasma of preterm hypoxic newborns at birth (8). Sick preterm newborns may be particularly exposed to FR in the first postnatal week because of frequent intensive care, involving oxygen supply, assisted ventilation, surfactant administration, and total parenteral n...

Optimal Oxygenation of Extremely Low Birth Weight Infants: A Meta-Analysis and Systematic Review of the Oxygen Saturation Target Studies

“…The understanding that oxidative stress is not only caused by oxygen represented a fundamental leap forward [6]. A number of free radical generating systems were identified after we first understood the important role of the oxygen radical generating system hypoxanthine-xanthine oxidase as an explanation of reoxygenation injury [7,8,9,10]. …”

Prevalência de asfixia perinatal e encefalopatia hipóxico-isquêmica em recém-nascidos de termo considerando dois critérios diagnósticos

“…Desse total de nascimentos, 9427 foram de recém nascidos de termo e destes 30 RN apresentaram asfixia, sendo assim, a prevalência de asfixia observada neste estudo foi de 3,2 por 1000 nascimentos a termo (IC a 95% -[2,1 por mil; 4,5 por mil]). Quando utilizado o critério 1 (ACOG/AAP), esta prevalência foi de 0,64 por 1000 nascimentos a termo (IC a 95% -[0,3 por mil; 1,5 por mil]) e pelo critério 2 (Buonocore et al) 11 Em relação às características maternas observou-se diferença estatisticamente significante entre os RN dos grupos dos critérios 1 e 2 no que se refere ao tipo de parto. Enquanto no grupo do critério 1 a maioria dos partos foram cesáreas (57%) no grupo do critério 2 a maioria dos partos foram vaginais (87%).…”

“…Entre os escores que medem a gravidade do comprometimento neurológico do RN com EHI, citamos o de Sarnat e Sarnat 9 (1976), que classifica o paciente em três estágios conforme o nível de consciência, o tônus muscu-Abstract: Objectives: to verify the prevalence of asphyxia and hypoxic-ischemic encephalopathy in term newborns according with two diagnostic criteria; To assess the neurological evolution according with each one of the criteria. Method: prospective cohort study with 30 newborns by means of two different diagnostic criteria at birth: criterion 1 preconized by the ACOG/ APP, 1996 of (cord pH > 7,0, dysfunction of multiple organs, neurological manifestations in the first week of life beyond the Apgar between 0-3 in 5 minutes); the criterion 2 was defined by Buonocore et al, in 2002, as amended (> cord pH of 7,2, Apgar score of 4-6 at 5 minutes and need to maintain FIO 2 > 0.40 of saturation 86%); Results: the prevalence of asphyxia with the criterion 1 was 0,64 per 1,000 termlin births and with the criteriom 2 1,1 per 1000 termlins birth. Among the 30 NB with asphyxia diagnoses, the hypoxic isquemic encephalopathy was 53%.…”

“…Não existe ainda um consenso único para definir asfixia perinatal, o que justifica a dificuldade dos da-dos de prevalência e a discrepância em relação aos trabalhos da literatura. Os mais utilizados são os do Colégio Americano de Obstetrícia e Ginecologia 10 (ACOG) junto aos da Academia Americana de Pediatria (AAP) de 1996, que 11 , que definem asfixia perinatal pela presença de dois dos seguintes parâmetros: pH da veia umbilical ≤ 7,20, valor de Apgar no quinto minuto de vida inferior a 6, e necessidade de fração de oxigênio inspirada (FiO 2 )³ 0,40 para manter saturação de oxigênio 86% ao nascimento.…”

Enzyme Activities in Erythrocytes of Term and Preterm Newborns

“…20 This could be a consequence of RBC increased exposure to free radicals, starting at delivery and persisting in the following days. 21 GSH recycling in neonatal RBC protects immature tissues of premature babies from peroxidative damage and compensates their deficient antioxidant capacity. It also counteracts ROS, produced in greater amount by fetal-type hemoglobin than by adult's hemoglobin, and it metabolizes oxidant species generated in body tissues by sudden exposure of the air/blood interface to elevated oxygen tension.…”