Risk factors and clinical outcomes of pulmonary interstitial emphysema in extremely low birth weight infants.

OBJECTIVE: We studied the ante- and postnatal risk factors and clinical outcomes associated with pulmonary interstitial emphysema (PIE) in extremely low birth weight infants (ELBW, <1000 g at birth) in the present era of tocolytics, antenatal steroid and postnatal surfactant administration.

STUDY DESIGN: This was a retrospective case-controlled study of all ELBW admitted consecutively during a designated study-period in a level III nursery. Data were analyzed by performing univariate and multivariate analysis as applicable.

RESULTS: Infants with PIE had lower 1 and 5 min Apgar scores (P=0.04 and 0.003 respectively), increased surfactant utilization (P=0.004), higher maximum inspired oxygen concentration (P=0.04) and mean airway pressure administration (P=0.02) during the first week of life, and increased neonatal mortality (P=0.01). They received higher antenatal doses of magnesium sulfate (MgSO(4)) (P=0.02). 56% of infants with PIE were exposed to more than 10 g of MgSO(4) (Mg10), compared to 15% in non-PIE group (P=0.01). The multivariate logistic regression analysis including significant co-variates revealed an independent association between Mg10 and PIE (P=0.01, Odds ratio 19.8, 95% CI 1.5-263).

CONCLUSION: Pulmonary interstitial emphysema is associated with increased mortality in ELBW infants. Mg10 is an independent risk factor for PIE in this population.