Surfactant treatment at birth reduces lung vascular injury and edema in preterm lambs

To study the effect of surfactant administration on fluid balance in the premature lung, we measured pulmonary vascular pressures, lung lymph and pleural liquid flow, and concentrations of protein in lymph, pleural liquid, and plasma before and after birth in 12 chronically catheterized preterm lambs (127-128 d gestation) treated with either placebo or surfactant just before surgical delivery. Eight lambs received intrapulmonary saline (placebo), and four lambs received surfactant; all lambs were mechanically ventilated with O2 for 8 h after birth. In control lambs, lung lymph and pleural liquid flow increased from 2.7 +/- 0.4 mL/h during the 2-4 h before birth to 9.2 +/- 2.1 mL/h by 6-8 h after birth; lymph and pleural space protein drainage increased from 58 +/- 7 mg/h during the 2-4 h before birth to 134 +/- 25 mg/h by 6-8 h after birth. In lambs treated with surfactant, there was no significant increase in lymph and pleural liquid flow after birth (before birth, 2.3 +/- 0.3 mL/h; 6-8 h after birth, 3.4 +/- 0.9 mL/h); likewise, lymph and pleural space protein drainage did not change after birth (before birth, 54 +/- 6 mg/h; 6-8 h after birth, 50 +/- 8 mg/h). Postmortem extravascular lung water was significantly less in lambs treated with surfactant compared with control lambs (control, 6.5 +/- 0.3 g/g dry lung; surfactant-treated, 5.0 +/- 0.2 g/g dry lung).(ABSTRACT TRUNCATED AT 250 WORDS)