Anesthesia for non-obstetric surgery during late term pregnancy in mares

Submitting late-term pregnant mares to anesthesia for non-obstetric surgery raises concerns about the survival of the mother and fetus. This study aimed to evaluate and describe transient maternal and fetal hemodynamic changes during general inhalation anesthesia in mares during the last month of gestation. Nine adult mares in the last month of gestation were subjected to general inhalation anesthesia and dorsal recumbency for 90 minutes. Trans-anesthetic vital parameters, arterial hemogasometry, cardiac output, pulmonary arterial pressure, central venous pressure, and fetal heart rates were assessed at defined intervals. During various timespans of the anesthetic procedure, the mares demonstrated an increase in heart rate, mean arterial pressure, and diastolic pressure as well as a decrease in temperature. Additionally, arterial hemogasometry indicated respiratory acidosis. No changes in cardiac output were observed; however, there was a reduction in pulmonary arterial and central venous pressures and stroke volume. Fetal heart rate was significantly decreased. General inhalation anesthesia in late term pregnancy in mares in a recumbent position implies in significant hemodynamic and metabolic changes. Up to 90 minutes those changes does not seem to affect negatively the maternal-fetus prognosis.