Analgesia for labour and delivery using incremental diamorphine and bupivacaine via a 32-gauge intrathecal catheter.

Twenty mothers who had requested regional analgesia during labour had a 32-gauge catheter inserted into the lumbar subarachnoid space. The mean time to place the catheters was 116 s (range 55-270 s) and there were no technical difficulties. Incremental diamorphine was given, up to a maximum initial dose of 0.5 mg. Analgesia was excellent in 11 mothers, good in seven and unsatisfactory in two. The duration of initial analgesia from diamorphine was 101 min (range 30-170 min). Eight mothers were able to move about during the first stage, with effective analgesia. Side effects were common: 15 mothers had pruritus, 15 had nausea or vomiting, and eight had mild sedation. No mother had a ventilatory frequency of less than 12 b.p.m. in the 12 h after the last dose of intrathecal diamorphine. Intrathecal 0.5% bupivacaine was given to 16 mothers in the first stage because the analgesia after a top-up with diamorphine became insufficient later in the labour. Fifteen mothers were pain free after bupivacaine; there was one failure. The initial effective dose of bupivacaine was between 0.25 ml and 2 ml. The maximum height of the block after bupivacaine was T9, and there was no hypotension. Nine mothers were given hyperbaric 0.5% bupivacaine 1-2 ml during the second stage; all were pain free for the procedure. The maximum force needed to withdraw the catheters was 700 g; and all catheters were removed intact. There were no post-spinal headaches.