Terbutaline-induced changes in ovine, fetal and maternal hemodynamics, and fetal electroencephalogram

Terbutaline has been used in obstetrics to treat premature labor. Its effect was studied in six ewes and their fetuses at gestational ages of 140 +/- 0.5 days (term approximately 147 days). Terbutaline (1,500 microgram) was infused over 34.5 minutes to the six anesthetized ewes. Post-baseline changes of maternal and fetal blood pressure (MBP, FBP), heart rate (MHR, FHR) and acid-base values, uterine blood flow (QUA), fetal cerebral blood flow (QFC), and fetal cerebral function (EEG) and metabolism were studied at 10, 20, 30 and 60 minutes. Terbutaline caused maternal tachycardia, hypotension, metabolic acidosis, hyperglycemia, and mild lactic acidemia without affecting PO2, O2 saturation (O2%), O2 content, or uterine blood flow. In the fetus, metabolic acidosis, lactic acidemia, hyperglycemia, and increased glucose consumption resulted, whereas PO2, PCO2, O2 consumption, fetal cerebral blood flow, heart rate, blood pressure, and EEG remained unchanged. It is suggested that terbutaline, although causing transient maternal tachycardia and hypotension, does not decrease uterine blood flow or alter fetal PO2 or EEG. It is further suggested that it reduces maternal and fetal pH due to lactic acidemia.