Extradural infusion of 0.125% bupivacaine at 10 ml h-1 to women during labour.

One hundred primigravidae were allocated randomly to receive either an extradural infusion of 0.125% bupivacaine (Marcain) 10 ml (12.5 mg) per hour during labour, or no infusion. Both groups had intermittent "top-ups" of 0.5% bupivacaine when indicated. The mean interval between top-ups was significantly longer in the infusion group (218 min v. 152 min). Seventy-six percent of the mothers in the infusion group required no or only one top-up. Although the infusion patients received a higher mean dose of bupivacaine (178 mg v. 130 mg), there was no difference between the groups with respect to mode of delivery, need for urinary catheterization, adverse cardiovascular effects on mother or fetus, or the time taken after delivery to recover sensation and motor power. The only real disadvantage was that the infusion group had an increased incidence of lower limb weakness (64% v. 44%). The neonates had similar Apgar scores, times to sustained respiration and requirements for resuscitation. The technique, therefore, should be safe if coupled with testing of sensory level, as no block extended higher than T6.