Effects of magnesium sulfate on the fetal heart rate response during acute hypoxemia in goats.
OBJECTIVE
The effects of magnesium sulfate on fetal heart rate (FHR) response during acute hypoxemia in goats were investigated.


METHODS
The FHR responses due to hypoxemia during magnesium sulfate infusion (Mg study) were compared with those during vehicle infusion (controls) in six chronically instrumented goat fetuses at 125-130 days' gestation.


RESULTS
Four-hour infusions of magnesium sulfate significantly increased fetal plasma concentrations of magnesium from 2.3 to 6.5 mg/dL. During the hypoxemic period, the fetal arterial oxygen pressure was significantly decreased from 29.0 +/- 2.5 to 14.6 +/- 2.6 torr in the controls, and from 28.9 +/- 3.9 to 13.7 +/- 4.7 torr during the Mg study. Neither arterial carbon dioxide pressure nor pH was significantly altered. In the controls, FHR was significantly decreased by hypoxemia, accompanied by increases in variability. In the Mg study, FHR was not significantly decreased by hypoxemia. Acute hypoxemia also increased the FHR variability during magnesium infusion, which was significantly reduced compared with those in the control population.


CONCLUSIONS
Magnesium sulfate masks FHR-slowing responses during acute hypoxemia in fetal goats.
Sameshima
H
H
Department of Obstetrics and Gynecology, Kagoshima City Hospital, Japan.
Ikenoue
T
T
Kamitomo
M
M
Sakamoto
H
H
D000818:Animals; D001794:Blood Pressure; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D005311:Fetal Hypoxia / Q000503:physiopathology*; D006041:Goats; D006340:Heart Rate, Fetal / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000097:blood; D008278:Magnesium Sulfate / Q000494:pharmacology*; D010100:Oxygen / Q000097:blood; D011247:Pregnancy
D008278:Magnesium Sulfate; D008274:Magnesium; D010100:Oxygen