Lung inflammation and pulmonary function in infants with meconium aspiration syndrome

Objective: To evaluate the relationship between inflammation and pulmonary function, we quantified changes in inflammatory cellular profile, pro-inflammatory cytokines, and pulmonary function in intubated neonates with meconium aspiration syndrome (MAS). Methods: Sixteen term infants were studied. Tracheal aspirate fluids, obtained within the first 6, 24, 48, and 96 hr of life were used for measurements of: (1) cellular profile changes; (2) mRNA and protein levels for pro-inflammatory cytokines, IL-6, IL-8, and TNF-alpha, using RT-PCR and ELISA. Using the same time points as above, we determined mean airway pressure, oxygenation index (Ol), alveolar-arterial oxygen gradient, and arterial/alveolar oxygen ratio. Baseline tidal volume and pulmonary compliance were obtained. Results: Birth weight was 3,820 1656 g, gestational age 39.8 +/- 1.4 weeks. Mean airway pressure and 01 significantly decreased from the first 6-96 hr of age (P=0.01, P=0.027). Cell counts were elevated in the first 6 hr compared to 96 hr (17.4 x 10(6)/ml VS. 1.5 x 10(6)/ml, P < 0.05). Pro-inflammatory cytokines decreased from the first 6-96 hr: IL-1 beta (187 vs. 37 pg/ml, P < 0. 05); IL-6 (3,469 vs. 150 pg/ml, P < 0.05); IL-8 (16,230 vs. 6,334 pg/ml, P=0.01). Conclusions: MAS is associated with an inflammatory response characterized by the presence of elevated cell count and pro-inflammatory cytokines which significantly decreased by 96 hr of life. This decrease in lung inflammation has a positive correlation with corresponding decreases in mean airway pressure and oxygenation index, two parameters associated with improved pulmonary function.