Labetalol does not decrease placental perfusion in the hypertensive term-pregnant rat.
The acute effect of labetalol hydrochloride, a combined nonspecific beta-adrenergic and postsynaptic alpha 1-adrenergic blocker, on maternal hemodynamics and organ perfusion was investigated in 10 hypertensive, term-pregnant, spontaneously hypertensive rats with the use of the radioactive-labeled microsphere technique. The normal fall in blood pressure during pregnancy was prevented by the reduction of litter size to two conceptuses on day 7 of gestation. Labetalol (1 to 6 mg/kg) effectively lowered mean arterial pressure 22% by decreasing cardiac output 16%; total peripheral resistance was not significantly decreased. Thus, the blood pressure lowering effect of labetalol was due primarily to its beta-adrenergic blocking effect. Regional flows to the carcass and splanchnic circulation were decreased 19% and 15%, respectively, after labetalol administration. Uterine wall and ovarian perfusion were significantly reduced, but placental perfusion was not significantly altered. Because labetalol lowers blood pressure without reducing placental perfusion, it may be a useful alternative to hydralazine for the treatment of hypertensive emergencies in pregnancy.
Ahokas
R A
RA
Department of Obstetrics and Gynecology, University of Tennessee, Memphis 38163.
Mabie
W C
WC
Sibai
B M
BM
Anderson
G D
GD
D000818:Animals; D005260:Female; D005836:Genitalia, Female / Q000098:blood supply; D006439:Hemodynamics / Q000187:drug effects; D006973:Hypertension / Q000503:physiopathology*; D007741:Labetalol / Q000494:pharmacology*; D009132:Muscles / Q000098:blood supply; D010920:Placenta / Q000098:blood supply* / Q000187:drug effects; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000503:physiopathology*; D051381:Rats; D011918:Rats, Inbred SHR; D012039:Regional Blood Flow / Q000187:drug effects; D013152:Splanchnic Circulation / Q000187:drug effects
D007741:Labetalol