We studied the effects of spinal anaesthesia (Group S), epidural anaesthesia (Group E), and combined spinal and epidural anaesthesia (Group SE), on maternal and fetal blood flow in 24 healthy parturients (n = 8/group) with uncomplicated singleton pregnancies using Doppler technique. Prior to the induction of anaesthesia, the patients were prehydrated with balanced electrolyte solution 15 ml.kg-1 over a period of 15 min. After the induction of regional anaesthesia, the systolic blood pressure was maintained within 15% limits of the preoperative values using prophylactic etilefrine infusion in Groups S and SE. The flow velocity waveforms of the maternal femoral artery, the main branch of the uterine artery (placental side), the foetal umbilical and middle cerebral arteries were recorded by Doppler technique before and after prehydration as well as after onset of T7 analgesia and the pulsatility indices (PI) were derived. Rapid intravenous prehydration had no effects on uteroplacental or fetal circulation as indicated by unaltered uterine, umbilical, and fetal middle cerebral artery PIs. After the onset of T7 analgesia, the uterine artery PI was increased in Group S indicating increased uterine vascular resistance while no changes occurred in Groups E and SE. No adverse effects were observed on the neonates as indicated by the Apgar score and the umbilical artery and vein acid-base status in any of the groups.
A prospective randomized study was performed to investigate the effect of a short-term ritodrine infusion on the concentrations of maternal and fetal prostaglandins and their precursor fatty acids. Mothers gave birth by an elective cesarean section at term, and either ritodrine (study group) or physiological saline (controls) was infused 2 h prior to the operation. Ritodrine decreased the levels of thromboxane A2 significantly in the mother, while the concentration of prostacyclin remained unchanged. In the umbilical arterial plasma concentrations of prostacyclin or thromboxane A2 there were no differences between ritodrine-treated and control subjects. Ritodrine had no effect on the prostaglandin precursor fatty acids and other fatty acids of plasma phospholipids of the mother or her fetus. It is concluded that ritodrine may suppress the maternal prostaglandin production, but has no effect on the levels of vasoactive prostaglandins or their precursor fatty acids in the fetus.
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