Cumulative index of exposure to hypocarbia and hyperoxia as risk factors for periventricular leukomalacia in low birth weight infants

BACKGROUND. Hypocarbia and hyperoxia are risk factors for periventricular leukomalacia in low birth weight infants. The association of a cumulative index of exposure to hypocarbia and hyperoxia and periventricular leukomalacia has not been evaluated. OBJECTIVE. Our goal was to examine the relationship between cumulative index of exposure to hypocarbia and hyperoxia and periventricular leukomalacia during the first 7 days of life in low birth weight infants. METHODS. Blood gas results were recorded in 6-hour intervals among low birth weight infants in a prospective data registry. Cumulative index of exposure to hypocarbia was calculated as the difference between arterial carbon dioxide level and 35 mm Hg multiplied by the time interval in hours for each 6-hour block in a 24-hour day for the first 7 days of life. Cumulative index of exposure to hyperoxia was calculated in the same manner for arterial oxygen level > 80 mm Hg. The relationship between exposure to hypocarbia, hyperoxia, and periventricular leukomalacia was examined in 778 infants with blood gas and cranial sonography data. RESULTS. Twenty-one infants had periventricular leukomalacia. Hypocarbia occurred in 489 infants and hyperoxia in 502 infants. Infants with periventricular leukomalacia were more likely to have a lower gestational age and to require delivery room resuscitation than those without periventricular leukomalacia. More infants in the highest quartile of exposure to hypocarbia had periventricular leukomalacia compared to those with no hypocarbia. Risk of periventricular leukomalacia was increased in infants with the highest quartile of exposure to hypocarbia after adjusting for maternal and neonatal variables, none to be associated with periventricular leukomalacia. Cumulative index exposure to hyperoxia was not related to periventricular leukomalacia. CONCLUSIONS. Cumulative exposure to hypocarbia and not hyperoxia was independently related to risk of periventricular leukomalacia in low birth weight infants.