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11 non-pregnant sheep were prepared for chronic studies with an electromagnetic flow transducer placed around one uterine artery and with catheters in both uterine veins, aorta and inferior vena cava. The 4 local anaesthetics bupivacaine, etidocaine, lignocaine and chloroprocaine were infused intravenously on consecutive days in a randomized manner. During the infusions of all 4 local anaesthetics, uterine blood flow decreased due to an increase of uterine vascular resistance. The uterine arteriovenous O2-difference increased, while the uterine O2-consumption decreased without development of an acidosis of the uterus. The same changes were observed in 8 animals, to which oestrone had been administered intravenously prior to the infusions of local anaesthetics. Local anaesthetics had the same effects in the non-pregnant and pregnant uterus. A direct vasoconstrictive mechanism on the uterine vessels as well as a depressing effect on metabolism is discussed for the local anaesthetics.

Pulmonary venous admixture (Qs/Qt) was determined in nine nonpregnant sheep and in seven pregnant sheep during their last trimesters of gestation. Pulmonary venous admixture was greater in the pregnant animals (5.7 +/- 1.6% of the cardiac output; mean +/- SD) than in the nonpregnant ones (4.2 +/- 1.3%; p less than 0.05). On consecutive days, four local anesthetics were infused in random order via a femoral venous catheter into each sheep for 30 minutes. Total doses of 1.8 mg/kg of bupivacaine, 2.7 mg/kg of etidocaine, 6 mg/kg of lidocaine, and 15 mg/kg or chloroprocaine were administered. None of the anesthetics induced a significant change in pulmonary venous admixture.

The local anesthetics bupivacaine, etidocaine, lignocaine and chloroprocaine were infused intravenously for 30 min to pregnant sheep, prepared for chronic studies. The amide compounds reached highere plasma concentrations than chloroprocaine. All local anaesthetics decreased uterine blood flow and O2 consumption without marked alterations of arterial or uterine venous blood gases. These changes were within the wide physiological range of variation, which was established in controls during 24 h. The findings may be of significance during paracervical block or pathological states of UBF or fetal homeostasis.