Cerebral oxidative metabolism in fetal sheep with multiple-dose ethanol infusion

Cerebral oxidative metabolism and cotylendonary blood flow were measured in 10 unanesthetized fetal sheep (127 to 132 days' gestation) during a control period, after the first, third, and fourth infusions of four doses of 0.5 gm of ethanol per kilogram of maternal body weight infused into the ewe during 5 hours, and 24 hours after ethanol infusion. Preductal arterial and sagittal vein blood samples were analyzed for oxygen content, blood gases, pH, and ethanol. Cerebral and cotylendonary blood flow were measured with a radioactive microsphere technique. Fetal blood gases and pH changed little with the ethanol infusions, although PaO2 and oxygen content decreased 24 hours after ethanol infusion. Cotylendonary blood flow, which was decreased after the third and fourth ethanol infusions, did not account for these delayed hypoxemic changes. Similarly, cerebral oxidative metabolism was decreased when measured after each of the ethanol infusions, with no dose response or tolerance evident. This noted fall in fetal cerebral oxidative metabolism appears to be a direct depressant effect that was maximal at rather low fetal ethanol levels, which, if prolonged, might well affect cerebral growth and development. Recovery of cerebral metabolic function appeared complete by 24 hours. However, relative fetal hypoxemia was evident at this time, the mechanism of which remains to be determined.