EFFECTS OF HYPOCAPNIA ON THE DEVELOPMENT OF CYSTIC PERIVENTRICULAR LEUKOMALACIA IN PREMATURE-INFANTS TREATED WITH HIGH-FREQUENCY JET VENTILATION

Background and Objective. Previous data from our institution indicate that mechanically ventilated premature infants are at increased risk f or cystic periventricular leukomalacia (CPVL), particularly if hypocap nia occurs. High-frequency jet ventilation (HFJV) may produce substant ial hypocapnia. We sought to investigate whether hypocapnia during HFJ V is associated with the development of CPVL. Methods. Sixty-seven pre mature infants (mean gestational age, 27.2 weeks; mean birth weight, 1 001 g) underwent HFJV for a mean of 44 (range, 8 to 70) hours during t he first 3 days of life. All infants were followed with serial neuroso nograms at least weekly until 6 to 8 weeks of age and every 2 to 4 wee ks thereafter until discharge. To assess the cumulative effects of hyp otension, acidosis, hypoxemia, and hypocarbia during the first 3 days of life on the development of PVL, we developed a quantitative assessm ent in which we assigned threshold levels at particular critical value s of these parameters (such as a mean Pace, of 20 mm Hg) and calculate d an area above the curve between longitudinally connected values of t hese parameters and the threshold levels. Results. Nine of the 67 infa nts died before 21 days of life. Of the 58 who survived beyond 21 days , large CPVL (>5 mm in size) developed in 18 infants. Infants with cys ts were similar in birth weight, gestational age, and virtually all ot her antepartum, intrapartum, and postpartum parameters compared with t he 40 neonates in whom CPVL did not develop. However, infants with CPV L were significantly more likely to have moderate or severe periventri cular echodensities preceding development of CPVL and periventricular echodensities that persisted for a longer period. We did not find an e ffect of hypotension, acidosis, or hypoxemia on the development of CPV L. There were no differences in the mean Pace, the absolute low PaCO2 values, the ranges of low PaCO2, between groups, or area above the cur ve measurements at threshold levels of 15 and 20 mm Hg, respectively. However, logistic regression analysis revealed that infants with CPVL were independently significantly more likely to have greater cumulativ e hypocarbia below a threshold level of 25 mm Hg during the first day of life (odds ratio, 5.43; 95% confidence interval, 1.33 to 22.2). Con clusions. Hypocarbia produced by treatment with HFJV during the first 3 days of life is associated with the subsequent development of CPVL. The mechanisms for the development of CPVL among premature infants tre ated with HFJV need to be established.