Effect of propranolol on the acid base balance and hemodynamics of 'chronically instrumented' pregnant sheep.

Abstract

Maternal and fetal responses to i.v. admission of propranolol (4 mg/4 min) were investigated in 10 'steady-state' sheep experiments performed on 5 ewes and their fetuses at 101-128 days of gestation. Observations were made at 0, 5, 15, 30, 45, 60, 75, 90 and 120 min from the start of infusion. Transient decrease in fetal heart rate (p less than 0.05) was observed at 15 min, accompanied by fetal acidosis, which persisted throughout the experiment. Mean fetal pCO2 increased significantly at 5, 15 (p less than 0.025) and 75 min (p less than 0.05). Fetal pO2 decreased at 15 min (p less than 0.025). Oxygen saturation (O2%) decreased at 15 (p less than 0.001) and 60 min (p less than 0.025). Concomitant decreases in O2 content were noted at 15 (p less than 0.005), 30 (p less than 0.05), 60 (p less than 0.025) and 90 min (p less than 0.05). Mean fetal base excess decreased at 30 min (p less than 0.05). Mean maternal heart rate decreased at 15 (p less than 0.010) and 30 min (p less than 0.005), followed by an increase at 75 (p less than 0.05) and 90 min (p less than 0.05). Mean uterine blood flow remained unchanged during infusion and up to 90 min. However, it increased at 105 (p less than 0.025) and 120 min (p less than 0.05). It is suggested that propranolol causes definite fetal adverse effects and its usage during pregnancy must be limited to absolutely indicated situations.