The Effects of Medetomidine on Maternal and Fetal Cardiovascular and Pulmonary Function, Intrauterine Pressure and Uterine Blood Flow in Pregnant Goats

Abstract

To investigate the effects of medetomidine on late pregnant goats, medetomidine induced changes in maternal or fetal circulation and acid-base balance, as well as changes in intrauterine pressure (IUP) and uterine blood flow (UBF), were studied. Intramuscular administration of medetomidine (40 μg/kg b.w.) decreased the heart rate (HR) and arterial blood pressure (ABP) of the mother, and the change in HR was significant statistically (p<0.05). In the fetus, HR and ABP showed a transient decrease and increase (p<0.05), respectively. A decrease in maternal arterial blood pH and oxygen partial pressure (PO₂) and an increase in carbon dioxide partial pressure (PCO₂) were recorded after the injection, but none was significant. In the fetus, arterial blood PO₂ decreased significantly (p<0.05) after 5 min of administration, and a significant metabolic acidemia supported by a decrease in base excess was observed. Within 1 to 4 min after the administration of medetomidine, IUP began to rise and remained high for 10 to 14 min. Thereafter, the rise in IUP was frequent and periodical. After the injection, UBF significantly (p<0.05) decreased, and the fall in UBF was associated with a rise in IUP. The maternal and fetal serum medetomidine concentration increased remarkably after the injection of medetomidine into the mother. These observations in late pregnant goats suggested that medetomidine induced a decrease in maternal cardiac output, a decrease in UBF arising from the induction of uterine contractions, and transplacental medetomidine can have a suppressive effect on the fetus.