Fetal responses to maternal and fetal methamphetamine administration in sheep.
OBJECTIVE
The current study was designed to test the hypothesis that maternally administered methamphetamine decreases fetal PaO2 by reducing uterine blood flow and to determine the cardiovascular and blood gas responses to varying doses of methamphetamine given both to the fetus and the mother.


METHODS
Nine near-term pregnant sheep were surgically instrumented to measure maternal and fetal blood pressure and heart rate and uterine and umbilical blood flow. Fetal blood gases and pH were determined before and after each dose of methamphetamine. Methamphetamine 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
Maternal methamphetamine administration produced a dose-related increase in maternal and fetal blood pressure and uterine vascular resistance, whereas uterine blood flow decreased in a dose-related fashion. Umbilical blood flow tended to increase slightly, but this did not reach significance. Fetal PaO2 decreased significantly, whereas fetal pH decreased only modestly. Direct fetal administration of methamphetamine produced dose-related increases in fetal blood pressure and umbilical blood flow and a significant decrease in fetal pH but no change in fetal PaO2.


CONCLUSIONS
The fetal PaO2 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 methamphetamine on the fetus.
Stek
A M
AM
Department of Obstetrics and Gynecology, University of Cincinnati College of Medicine, OH 45267-0526, USA.
Baker
R S
RS
Fisher
B K
BK
Lang
U
U
Clark
K E
KE
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005268:Femoral Vein; D005333:Fetus / Q000187:drug effects / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007275:Injections, Intravenous; D008431:Maternal-Fetal Exchange; D008694:Methamphetamine / Q000008:administration & dosage / Q000494:pharmacology*; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D010920:Placenta / Q000502:physiology; D011247:Pregnancy; D012039:Regional Blood Flow / Q000187:drug effects; D012756:Sheep; D013997:Time Factors; D014599:Uterus / Q000098:blood supply*; D014655:Vascular Resistance / Q000187:drug effects
D008694:Methamphetamine; D010100:Oxygen