Mechanical ventilation alters the immune response in children without lung pathology

Abstract.

Objective: This study was undertaken to examine the hypothesis that mechanical ventilation in association with anesthesia would alter the cytokine profile in infants without preexisting lung pathology. Design and setting: Prospective observational study in pediatric intensive care unit in a university hospital. Patients: Twelve infants who were subjected to an uncomplicated diagnostic cardiac catheterization procedure were studied. All subjects were ventilated with a volume control mode, 0.3 FIO₂, 4 cmH₂O PEEP, and 10 ml/kg tidal volume. Volatile (servoflurane) anesthetics were given. Measurements and results: Tracheal aspirates and blood samples were obtained before and after 2 h of mechanical ventilation. In tracheal aspirates and in supernatants of stimulated whole-blood cultures cytokine concentrations were measured. In the tracheal aspirates the immune balance was characterized by a proinflammatory response pattern, with a significant increase in TNF-α and IL-6 concentrations; concentrations of anti-inflammatory mediators remained very low. The functional capacity of peripheral blood leukocytes to produce INF-γ, TNF-α, and IL-6 in vitro was significantly decreased. This was accompanied by a significant decrease in the killing activity of natural killer cells. Conclusions: Two hours of servoflurane and mechanical ventilation using a tidal volume of 10 ml/kg is associated with remarkable changes in the immune response in infants without preexisting lung pathology undergoing cardiac catheterization. In the lungs the immune balance favors a proinflammatory response pattern without detectable concentrations of anti-inflammatory mediators. The Th1 immune response by peripheral blood leukocytes was decreased. The observed change in Th1/Th2 balance in favor of Th2 cytokine activity may be a systemic adaptation to the proinflammatory milieu in the lung.