In Vitro Action of Meconium on Bronochomotor Tonus of Newborns with Meconium Aspiration Syndrome.

The conclusions suggest that meconium did not potentiate the constrictor action of acetylcholine and histamine in the tracheobronchial system and did not cause modulation of bronchomotor tonus in case of his aspiration. Meconium causes mild relaxation of smooth tracheal musculature with a mechanism which is not mediated by cyclooxygenase products, from tracheal epithelium or proteins. Also, direct activity in the smooth musculature of several tested acids seems to have no significant impact in increasing the tonus of respiratory airway of smooth tracheal musculature.