SURFACTANT THERAPY RESTORES GAS-EXCHANGE IN LUNG INJURY DUE TO PARAQUAT INTOXICATION IN RATS

Paraquat is a weed killer which causes often fatal lung damage in huma ns and other animals. There is evidence that the pulmonary surfactant system is involved in the pathophysiology: of respiratory failure afte r paraquat intoxication and, therefore, the possible therapeutic effec t of intratracheal surfactant administration on gas exchange in rats w ith progressive lung injury induced by paraquat poisoning was studied. In one group of rats, the time course of the development of lung inju ry due to paraquat intoxication was characterized. In a second group o f rats, 72 h after paraquat intoxication, the animals underwent mechan ical ventilation and only those animals in which the arterial oxygen t ension/inspiratory oxygen fraction (Pa, O-2/FI, O-2) decreased to belo w 20 kPa (150 mmHg) received exogenous surfactant (200 mg.kg(-1) body weight). Within 3 days the rats in group 1 developed progressive respi ratory failure, demonstrated not only by impaired gas exchange and lun g mechanics but also by increased minimal surface tension and increase d protein concentration in bronchoalveolar lavage fluid, In group 2, i ntratracheal surfactant administration increased Pa, O-2/FI, O-2 signi ficantly within 5 min (14.4+/-2.4 kPa (108+/-18 mmHg)) to (55.2+/-5.3 kPa (414+/-40 mmHg)) and sustained this level for at least 2 h, It is concluded that intratracheal surfactant administration is a promising approach in the treatment of severe respiratory failure caused by para quat poisoning.