Combined spinal-epidural analgesia in labour: comparison of two doses of intrathecal bupivacaine with fentanyl.

We have compared intrathecal bupivacaine 1.25 mg and fentanyl 25 micrograms (group A) with bupivacaine 2.5 mg and fentanyl 25 micrograms (group B), for combined spinal-epidural analgesia in 49 labouring parturients in a prospective, randomized, double-blind study. Onset and quality of analgesia were similar in both groups, with median visual analogue scale pain scores of 0 achieved in 5-10 min. Median duration of analgesia was longer in group B (median 120 (range 90-120) min) compared with group A (75 (75-105) min) (P = 0.013). Median upper sensory level was higher in group B compared with group A at 15 min (T6-7 vs T11, P = 0.003) and at 30 min (T6 vs T11-12; P = 0.001). Motor block was greater in group B: seven patients had a modified Bromage score > or = 1 compared with none in group A at 15 min (P = 0.017). Group B also had a greater decrease in arterial pressure. Patient-midwife satisfaction scores and other side effects were similar. We conclude that intrathecal bupivacaine 1.25 mg with fentanyl 25 micrograms provided analgesia of similar onset and quality compared with bupivacaine 2.5 mg and fentanyl 25 micrograms. Although the duration of analgesia was shorter, the incidences of motor block and hypotension were less with the smaller dose.