Intervillous blood flow during caesarean section with prophylactic ephedrine and epidural anaesthesia.

We administered a 15 mg i.v. bolus of ephedrine at the commencement of epidural blockade to nine healthy parturients scheduled for elective caesarean section. Nine other patients did not receive prophylactic ephedrine before epidural anaesthesia (control group). Lactated Ringer solution, 30 ml/kg, was infused before and during blockade, and left uterine displacement was used to minimize aortocaval compression. A133Xe i.v. technique was used to measure intervillous blood flow (IBF) before and 20-25 min after epidural block. The mean arterial pressure (MAP) decreased after epidural blockade in the ephedrine group by 0.67 +/- 0.8 (mean +/- s.d.) kPa and by 1.20 +/- 1.1 (mean +/- s.d.) kPa in the control group. In spite of the decrease in MAP, IBF increased by 6% in patients receiving ephedrine (N.S.), whereas it decreased by 11% in the control group (N.S.). In the ephedrine group there was in this preliminary study a trend to increasing IBF during falling perfusion pressure (MAP). The results of this preliminary study suggest that ephedrine will not affect IBF, but to prevent maternal hypotension ephedrine should be used as an i.v. infusion instead of a bolus injection.