Fetal and maternal hemodynamic and metabolic effects of maternal nitroglycerin infusions in sheep

OBJECTIVES: We previously demonstrated effective tocolysis with nitroglycerin in laboring sheep. In this study we evaluated maternal and fetal circulatory effects of nitroglycerin. STUDY DESIGN: Vascular catheters and an umbilical Doppler flow transducer were placed in eight ewes. Nitroglycerin was infused maternally over 30 minutes at 1.5, 2.5, 5.0, and 10 mu g . kg maternal weight(-1) . min(-1). We recorded maternal and fetal variables before, at the end of each 30-minute infusion period, and 30 minutes later. Fetal regional flow distribution was measured with microspheres. Fetal oxygen, glucose, and lactate uptake were calculated. Data were analyzed by analysis of variance. RESULTS: There were no changes in fetal blood gas values, oxygen or substrate uptake, umbilical flow, output distribution, pressures, or heart rate. Maternal mean pressure fell and heart rate increased concomitantly. Maternal blood gases were unchanged. CONCLUSION: Nitroglycerin at tocolytic and greater doses had no adverse effects on fetal circulatory function during a 2-hour infusion.