The effect of hypoglycemia on fetal brain function and metabolism

Abstract

The effect of hypoglycemia on brain function in terms of the electroencephalogram (EEG) and on brain metabolism in terms of arteriovenous differences in substrate concentrations was studied in 11 in utero fetal sheep experiments. Fetal hypoglycemia was induced by an infusion of insulin to the ewe that resulted in maternal hypoglycemia. Carotid artery glucose concentration decreased to values that were 25 per cent of base line and as low as 3 mg. per 100 ml. The peak effect occurred 30 to 50 minutes following insulin infusion. The fetal EEG showed only minimal changes that consisted of a decrease in voltage and slowing on occasion. A significant decrease in heart rate occurred during the hypoglycemia. There was no significant change in oxygen consumption, blood flow, pH, or PCO2. A significant reduction (p < 0.005) occurred in the arteriovenous difference of both glucose and glucose consumption. The ratio of glucose to oxygen utilization was also significantly reduced (p < 0.01). There was no significant difference in the metabolism of lactate, pyruvate, and free fatty acids which suggests other undefined substrate utilization during hypoglycemia.