The effects of diazoxide upon fetal and maternal hemodynamics and fetal brain function and metabolism.

The effects of maternal infusion of Diazoxide (D) were evaluated in two groups of experiments: Nine ewes and their five nonhypoxic fetuses; the remaining four fetuses were excluded because of the development of hypoxia prior to the study. D was directly administered intravenously (IV) to the six fetuses. In group 1 maternal and fetal observations were made at 0, 5, 15, 30, and 45 minutes. A 60-minute observation was also made for the maternal infusion studies. Maternal infusion of 5 mg/kg maternal weight significantly reduced maternal pH from the control value at 5 minutes. Maternal metabolic acidosis was indicated by concomitant significant reductions in base deficit (BD) and total bicarbonate (HCO3), both of which remained low for all subsequent time periods. Maternal lactic acid concentration also increased at 15 minutes, although not significantly. Maternal PO2 also fell significantly at 5 minutes, remaining significantly low for the remaining observations. A profound maternal hypotension was elicited at 5 minutes. All following observations for maternal blood pressure (MBP) were also significantly low. Fetal carotid arterial (FCA) pH declined significantly from the control period value at 15 minutes, remaining significantly low for the remaining observations. FCA O2% saturation (O2%) also witnessed a significant decline from baseline for all observations. FCA serum lactate level rose at 15 minutes; however, this was not deemed significant. No significant changes were seen in fetal brain metabolic rate of oxygen or glucose. Fetal electroencephalogram (EEG) revealed a definite hypoxic change in a majority of cases. In group 2, the effects of a direct fetal IV administration of 30 mg D (mean dose = 7.97 mg/kg fetal weight) were studied in six experiments. No significant changes in fetal acid base status or fetal blood pressure (FBP) were witnessed for the 45 minutes under scrutiny. Fetal heart rate (FHR) showed a short transient rise from baseline at 5 and 15 minutes, returning to normal thereafter. A slight significant decrease in O2% saturation and O2 content were seen only for the 5-minute observation. There were no significant changes of fetal brain function and metabolism observed following D administration to the fetus. The significant fetal hypoxia and acidosis witnessed through the maternal infusion but not in the direct fetal bolus administration were probably owing to profound maternal hypotension resulting in deterioration of uteroplacental perfusion and fetal "gas exchange."