A TRIPLE-BLIND PLACEBO-CONTROLLED RANDOMIZED TRIAL OF ANTITHROMBIN THERAPY IN NEONATAL RESPIRATORY DISTRESS SYNDROME † 1035

Background: Although neonatal respiratory distress syndrome (RDS) is associated with decreased plasma activity of antithrombin (AT) and increased formation of thrombin, the benefits of therapy with AT have been uncertain. Objective: To test whether infusion of AT reduces thrombin formation, improves gas exchange and decreases the duration of mechanical ventilation and supplemental oxygen. Methods: 122 premature infants with RDS were randomized within 12 hours of life to pasteurized AT concentrate (Behringwerke AG, Germany) or placebo (1% albumin). A loading dose of 2 mL/kg (equivalent to 100 I.U. AT/kg) was followed by 1 mL/kg (50 I.U./kg) every 6 hours for 48 hours. Plasma AT activity. Thrombin-AT(TAT) complex and prothrombin fragment (F1+2) were measured every 12 hours during treatment. The arterial/alveolar oxygen tension (a/A) ratio and the ventilator efficiency index (VEI) were calculated every 6 hours during the 48 hr treatment phase and daily thereafter until day 7. Mechanical ventilation and oxygen therapy were considered terminated once they had been discontinued for at least 24 hours. The same exogenous surfactant was used in all study infants. Results: In the AT group (n=61), mean (SD) birthweight was 1198 (301) g, mean (SD) GA 28.3 (2.0) wks, 54% were male. In the placebo group(n=61), mean (SD) birthweight was 1201 (315) g, mean (SD) GA 28.8 (2.3) wks, 51% were male. In treated infants, AT activity was raised to means of 1.69 and 2.25 U/mL at 24 and 48 hrs respectively. Corresponding means in controls were 0.37 and 0.44 U/mL (p<0.0001). TAT and F1+2, however, were not significantly reduced by AT. VEI and a/A ratio were similar in both groups throughout the first week of life. Median days on initial mechanical ventilation were 6.3 (AT) versus 4.8 (placebo), p=0.27. Median days on supplemental oxygen were 7.4 (AT) versus 5.5 (placebo), p=0.30. There were 7(11.5%) deaths in the AT group and 3 (4.9%) deaths in the placebo group. Conclusion: Treatment with AT does not reduce biochemical markers of thrombin formation and does not improve gas exchange in neonatal RDS. Funded by the Physicians' Services Incorporated Foundation, Toronto, and Behringwerke AG.