Hemodynamic and acid-base effects of promazine on unanesthetized pregnant sheep and fetus

Although promazine has been used in obstetrics for over 20 years, its effects upon hemodynamic and acid-base conditions of steady-state pregnant sheep and fetus has not been sufficiently investigated. To study these effects, 10 experiments were performed in 5 ewes and their fetuses. Promazine (1 mg/kg/4 min) was administered intravenously to the ewes. Significant maternal changes included: reduction in hemoglobin from 9.1 +/- 0.43 to 8.4 +/- 0.43 g/100 ml at 120 min, O2 content from 12.1 +/- 0.61 to 10.8 +/- 0.59 vol% at 90 min, O2 saturation from 9.7 +/- 2.58 to 95.4 +/- 2.80% at 15 min, and blood pressure from 86.1 +/- 4.94 to 74.1 +/- 2.55 mm Hg at 45 min. The heart rate increased from 84 +/- 2.64 to 100 +/- 5.03 beats/min at 120 min. The uterine blood flow remained unchanged. The fetus developed mild metabolic acidosis as manifested by the reduction in pH from 7.375 +/- 0.008 to 7.35 +/- 0.005 at 45 min. No other fetal hemodynamic changes were observed. The significance of these findings is discussed.