Continuous subarachnoid infusion of 0.125% bupivacaine for analgesia during labour.

We have studied 20 primiparous women requesting pain relief for labour, to determine the feasibility of subarachnoid infusions of bupivacaine for analgesia. A 28-gauge catheter was inserted into the subarachnoid space through a modified 22-gauge Sprotte needle. After a bolus dose of up to 1.5 ml of 0.25% bupivacaine, a continuous infusion of 0.125% bupivacaine was commenced. If analgesia became inadequate, additional 0.5-ml boluses of 0.25% bupivacaine were given (mean number of top-ups 2.8; range 0-6). Persistent perineal pain occurred in four women and this was relieved by 0.5% hyperbaric bupivacaine. Analgesia was good or excellent in 15 of 20 mothers within 10 min and in 19 of 20 within 30 min, and it remained good or excellent throughout labour and delivery. Motor block was complete in three of the women who needed hyperbaric 0.5% bupivacaine. There were no difficulties with insertion of the catheter, no episodes of significant hypotension (systolic arterial pressure less than 100 mm Hg) or postdural puncture headache. Seven mothers delivered their babies vaginally, eight required assistance with forceps and five needed a Caesarean section.