The effects of corticosteroids and thyrotropin-releasing hormone on newborn adaptation and sympathoadrenal mechanisms in preterm sheep.

Abstract

We examined the effect of prenatal corticosteroids and thyrotropin-releasing hormone on postnatal adaptation and sympathoadrenal function in preterm lambs. Catheterized fetal lambs received saline solution (n = 6), corticosteroids alone (n = 8), or corticosteroids plus thyrotropin-releasing hormone (n = 6) for 60 hours. The lambs were delivered by cesarean section at a gestational age of 130 +/- 1 days. Ventilatory, cardiovascular, and metabolic responses and plasma catecholamine concentrations were measured for 2 hours after birth. Statistical analysis was performed by use of independent t tests or analysis of variance. Ventilatory function and cardiac contractility were significantly improved in both corticosteroid and corticosteroid plus thyrotropin-releasing hormone animals. Lambs treated with corticosteroid plus thyrotropin-releasing hormone had significantly higher aortic pressure and left ventricular blood pressure than either of the other groups. The postnatal norepinephrine and epinephrine surge was blunted in response to corticosteroid and corticosteroid plus thyrotropin-releasing hormone treatment. There were no differences in metabolic responses among the three groups. In premature lambs prenatal exposure to corticosteroids and thyrotropin-releasing hormone improves postnatal cardiovascular adaptation more than corticosteroids alone.