Disease severity is correlated with plasma clotting and fibrinolytic and kinin-kallikrein activity in neonatal respiratory distress syndrome.

This study was undertaken to determine whether simultaneous activation of clotting, fibrinolysis, and kinin-kallikrein is associated with disease severity in preterm infants with neonatal respiratory distress syndrome (RDS), during the first 5 d of life. In the infants with severe RDS, we found activation of clotting, fibrinolysis, and kinin-kallikrein within 6-12 h of birth, indicated by increased thrombin-antithrombin III complex formation [22.5 ng/ml versus 1.4 ng/ml (median values) in the mild/moderate RDS infants, p < 0.001], increased tissue-type plasminogen activator plasma concentrations [5.1 ng/ml versus 2.6 ng/ml (median values) in the mild/moderate RDS infants, p < 0.01], and increased plasma kallikrein activity [198% versus 189% of maximal activated human plasma (median values) in the mild/ moderate infants, p < 0.01], respectively. Thrombin generation, tissue-type plasminogen activator release, and kallikrein activity did not change significantly in the severe RDS group throughout the study. In these infants, kallikrein activity was accompanied by lower values of plasma kallikrein inhibitory activity. Activation of clotting, fibrinolysis, and kinin-kallikrein was accompanied with a transient decrease of the neutrophil count and a steady decrease of the platelet count in the severe RDS group. The studied parameters of clotting and fibrinolytic and kinin-kallikrein activation were significantly correlated with continuous measures of RDS severity. We, therefore, suggest that this activation process likely contributes to respiratory insufficiency in neonatal RDS.