Maternal treatment with B or TRH+B increases cardiac contractility and arterial pressure in preterm newborn lambs. Since it is not known whether these treatments have an effect in the cardiac output (CO) and organ blood flows, we measured these variables in 15 preterm newborn lambs ((83% G), whose mothers had received TRH+B (n=6): 400 μg TRH i.v. q/8h × 6 times and B: 12mg q/24 h × 2 times; B only (n=3): (same doses): Control (n=6): 50 ml 0.9%NaCL i.v. q/8h × 6 times. Fetuses were delivered by cesarean section and mechanically ventillated (PIP 32, PEEP 4 cm H2O, 40 breaths/min and FiO2 1). CO and its distribution was measured (45-60 min) by radiolabelled microespheres. The results were (X±SEM,*P<0.05 v C). Table

Table 1

The neonates treated with hormones had a higher peripheral perfusion and a lower percentage of the CO through the ductus arteriosus than controls. These values are similar to those foun in neonates of more advances gestational age. Our results indicate that the hormonal treatment enhances the cardiovascular function in preterm newborn lambs, improving postnatal cardiovascular adaptation. GrantFONDECYT 1930854, CHILE.