FETAL RESPONSES TO MATERNAL AND FETAL METHAMPHETAMINE ADMINISTRATION IN SHEEP

OBJECTIVES: The current study was designed to test the hypothesis that maternally administered methamphetamine decreases fetal Pao(2) by red ucing uterine blood Row and to determine the cardiovascular and blood gas responses to varying doses of methamphetamine given both to the fe tus and the mother. STUDY DESIGN: Nine near-term pregnant sheep were s urgically instrumented to measure maternal and fetal blood pressure ac id hear? rate and uterine and umbilical blood Row. Fetal blood gases a nd pH were determined before and after each dose of methamphetamine. M ethamphetamine was administered as intravenous bolus injections (30 to 35 minutes separating administration of each dose) into the maternal femoral vein in increasing doses of 0.03, 0.1, 0.3, and 1.0 mg/kg and on a separate days to the fetus into the hind limb vein as doses of 0. 03, 0.1, 0.3, 1.0, and 3.0 mg/kg estimated fetal weight. RESULTS: Mate rnal methamphetamine administration produced a dose-related increase i n maternal and fetal blood pressure and uterine vascular resistance, w hereas uterine blood flow decreased in a dose-related fashion. Umbilic al blood Row tended to increase slightly, but this did not reach signi ficance. Fetal Pao(2) decreased significantly, whereas fetal pH decrea sed only modestly. Direct fetal administration of methamphetamine prod uced dose-related increases in fetal blood pressure and umbilical bloo d flow and a significant decrease in fetal pH but no change in fetal P ao(2).. CONCLUSIONS: The fetal Pao(2) decrease observed after maternal administration of methamphetamine appears to be a result of decreased uteroplacental perfusion, whereas the observed changes in fetal blood pressure and fetal pH appear to be a result of the direct action of m ethamphetamine on the fetus.