The effect of maternal hyperglycemia on acid base balance and lung liquid production in the fetal sheep.

Abstract

In 10 chronically catheterized fetal sheep, the effects of 100 g of glucose infused (intravenous) to the pregnant ewe on lung liquid production and acid-base status were investigated. Maternal and fetal hyperglycemia occurred within 15 min of the infusion of glucose. There was a significant increase in fetal PCO2 from 41.67 +/- 1.00 to 46.89 +/- 1.83 mm Hg and a decrease in fetal arterial pH from 7.42 +/- 0.016 to 7.33 +/- 0.026 (n = 7). This acidosis was probably the result of fetal lactacidemia. There was also a decrease in fetal PO2 (p less than 0.001) following the infusion of glucose to the ewe. This, along with the acidosis, might account for the increased risk of unexplained fetal death in the diabetic pregnancy especially near term. Following the infusion of glucose to the ewe there was an increase in maternal plasma osmolality by 16 +/- 3.35 mosmol/kg (n = 9) and in fetal plasma osmolality by 14 +/- 2.64 mosmol/kg (n = 9; p less than 0.001). Fetal lung liquid production fell from 0.195 +/- 0.04 to 0.093 +/- 0.02 ml/min (n = 6; p less than 0.001). There was no change in the excretion of osmol by the lungs. The decreased lung liquid production was probably due to a decrease in the net movement of fluid across the pulmonary epithelium.