The effects of ephedrine and etilefrine on uterine and fetal blood flow and on fetal myocardial function during spinal anaesthesia for caesarean section.

The effects of two vasopressors, ephedrine and etilefrine, on blood flow in maternal uterine, fetal umbilical, middle cerebral and renal arteries and on fetal myocardial function were studied by colour Doppler and M-mode echocardiography techniques during spinal anaesthesia for caesarean section. There were 7 healthy pregnant women in each treatment group. The vascular resistance of maternal uterine arteries increased significantly after both of the vasopressors while the vascular resistance of the umbilical artery remained unchanged. Ephedrine decreased the blood velocity waveform indices in the fetal middle cerebral and renal arteries, increased fetal right ventricular contractility and decreased left ventricular inner end-diastolic dimension. Fetal heart rate was unchanged. Etilefrine caused no detectable changes in fetal haemodynamics or in fetal myocardial function. These findings demonstrate that vasopressors administered for the treatment of minor maternal arterial pressure fall produce vasoconstriction in the uterine circulation during spinal anaesthesia, yet healthy fetuses seem to tolerate these haemodynamic alterations well. On the other hand, ephedrine caused changes in fetal myocardial function and in the vascular resistance of fetal middle cerebral and renal arteries, which demonstrates the potential modifying effect of vasoactive drug given to the mother on fetal haemodynamics.