Effect of segmental epidural analgesia upon the uterine activity with special reference to the use of different local anaesthetic agents.

Segmental epidural block was given to 60 primiparous women during vaginal delivery, and the effect of the block on the uterine activity was studied after the first epidural injection. The women were divided into two main groups, according to whether or not oxytocin was used for stimulating the uterine contractions, and three different local anaesthetics--lidocaine-adrenaline, bupivacaine-adrenaline and plain bupivacaine--were tested. There was a transitory decrease in uterine activity in all women after the block was applied. In women with normal uterine activity before the block, a return to almost pre-analgesic values was noted within 30 min after the block, whereas in women treated with oxytocin there was still a reduction of 15-17% at this time. The reduction was caused by a decreasing intensity and at the same time an increase in the variability of the intensity, manifested as an increase in the coefficient of variation for this variable. There were no significant differences between the local anaesthetic agents tested, but addition of adrenaline to the bupivacaine solution resulted in a more marked decrease in uterine activity in women treated with oxytocin.