LIPID-PEROXIDATION AS A MEASURE OF OXYGEN-FREE RADICAL DAMAGE IN THE VERY-LOW-BIRTH-WEIGHT INFANT

Oxygen free radical mediated tissue injury is implicated as a major fa ctor in the pathogenesis of the long term complications seen in the pr emature infant, and direct evidence of their role in the development o f these long term problems is lacking. A prospective observational stu dy of 78% of very low birthweight infants admitted to a level III neon atal intensive care unit in 1992 was undertaken to determine the relat ionship between lipid peroxidation products, antioxidant activity, and outcome. Lipid peroxidation (malondialdehyde-thiobarbituric acid, MDA -TBA) and antioxidant activity (vitamin E and glutathione peroxidase a ctivity) were measured in 22 very low birthweight infants in the cord blood and the infant's blood at 24 hours, 48 hours, and 1 week of age and correlated with outcome measures. The normal range for these measu res was established in the cord blood samples of 48 consecutive health y full term infants. The concentration of MDA-TBA at 1 week correlated with the number of days of oxygen treatment and number of days of pos itive pressure ventilatory support. Controlling for gestational age an d antenatal complications simultaneously the MDA-TBA concentration rem ained significantly associated with the number of days of oxygen treat ment and the number of days of positive pressure ventilatory support. Glutathione peroxidase was low in the premature and full term infants consistent with the low concentrations of selenium known to be present in southern New Zealand. There was evidence of a quadratic relationsh ip between vitamin E at 1 week and the total number of days of supplem entary oxygen requirement, with both high and low values associated wi th increased oxygen requirement. This association, however, did not re main after controlling for gestational age and antenatal complications . These results support the role of oxygen free radicals in mediating tissue damage associated with the development of chronic lung disease in the premature infant.