Effect of extradural analgesia using bupivacaine and 2-chloroprocaine on intervillous blood flow during normal labour.

The effect of lumbar extradural analgesia on intervillous blood flow (IBF) during labour was studied in 26 healthy parturients using an i.v. bolus injection of xenon-133. There was a 19% decrease (n.s.) in mean IBF in six parturients (non-extradural control group). Mean IBF increased by 37.5% when 0.25% bupivacaine 10 ml was used and by 35.2% when 2% 2-chloroprocaine 10 ml was used (n.s.). When the two extradural groups were combined, the mean difference between IBF1 and IBF2 was 45 +/- 112 ml min-1 dl-1. This increase is statistically significant (P less than 0.05). The improvement in IBF after extradural block was considered to be a result of the decreased uterine vascular resistance, as no significant changes were observed in arterial pressure, uterine activity or uterine tone.