Differential effects of intravenous hydralazine on myoendometrial and placental blood flow in hypertensive pregnant ewes.
OBJECTIVE
The differential vasoactive effects of hydralazine on the uteroplacental vascular bed were studied.


METHODS
After control measurements were taken, near-term chronically prepared pregnant sheep were continuously infused with angiotensin II. Maternal arterial pressure was increased by 32 mm Hg. Hydralazine was then administered; the effects on regional resistance and blood flow were evaluated with a radionuclide-labeled microsphere technique. Analysis of variance for repeated measures was used to compare observations.


RESULTS
When compared with the hypertensive state, hydralazine caused the following changes by 40 minutes (mean +/- SEM): Although maternal blood pressure fell 31% +/- 5% (p = 0.0005), placental blood flow was unchanged, total uteroplacental blood flow increased 24% +/- 8% (p = 0.03), total uteroplacental resistance decreased 43% +/- 4% (p = 0.0002), placental resistance decreased 19% +/- 9% (p = 0.01), myoendometrial blood flow increased 390% +/- 82% (p = 0.0005), and myoendometrial resistance decreased 82% +/- 4% (p = 0.0005).


CONCLUSIONS
In angiotensin II-induced hypertensive ewes, hydralazine is an effective dilator of the uteroplacental vascular bed and can maintain placental blood flow while blood pressure.
Pedron
S L
SL
Department of Obstetrics and Gynecology, University of Wisconsin-Madison.
Reid
D L
DL
Barnard
J M
JM
Henry
J B
JB
Phernetton
T M
TM
Rankin
J H
JH
D000311:Adrenal Glands / Q000098:blood supply; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D004717:Endometrium / Q000098:blood supply*; D005260:Female; D006830:Hydralazine / Q000494:pharmacology*; D006973:Hypertension / Q000503:physiopathology*; D007275:Injections, Intravenous; D008863:Microspheres; D009215:Myometrium / Q000098:blood supply*; D010920:Placenta / Q000098:blood supply; D011247:Pregnancy; D012039:Regional Blood Flow / Q000187:drug effects; D012079:Renal Circulation / Q000187:drug effects; D012756:Sheep; D014655:Vascular Resistance / Q000187:drug effects
D000804:Angiotensin II; D006830:Hydralazine