Maternal and fetal responses to halothane in pregnant monkeys

Maternal cardiac output, blood pressure, heart rate, fetal blood pressure, heart rate and respiratory blood gases, and uterine blood flow were measured in six pregnant monkeys during halothane-nitrous oxide and oxygen anesthesia and compared to theses same parameters observed during nitrous oxide and oxygen anesthesia. Halothane 1.5% was associated with a decrease in maternal arterial pressure (54%), heart rate (10%), cardiac output (17%), total peripheral resistance (40%), and uterine blood flow (38%). Mean fetal heart rate decreased 18% and mean fetal blood pressure 22%. These changes in fetal hemodynamics were probably related to a direct depression of the fetal cardiovascular system and its usual compensatory mechanism as well as the fetal asphyxia secondary to the decrease in uterine blood flow.