Comparison of intrathecal and epidural diamorphine for elective Caesarean section using a combined spinal-epidural technique

To assess calculated equivalent doses of intrathecal and epidural opioids for elective Caesarean section in terms of quality and duration of analgesia, and incidence of side effects, we have compared 50 patients, allocated randomly to one of two groups to receive either diamorphine 0.25 mg intrathecally (group 1) or 5 mg epidurally (group 2), in addition to intrathecal bupivacaine 10 mg, using a combined spinal-epidural technique. There was no significant difference in duration of analgesia between groups (group 1 mean 14.6 (so 5.9) h, group 2 14.2 (6.5) h; mean difference 0.8 h; 95% CI -2.8-4.5; P = 0.65) or quality of analgesia (VAPS and VRS scores). The degree of pruritus was similar in both groups (80-88%) but the incidence of postoperative nausea and vomiting was significantly higher in the epidural group (24% vs 4%; P < 0.05). Intrathecal diamorphine 0.25 mg produced the same duration and quality of postoperative analgesia as epidural diamorphine 5 mg for elective Caesarean section but with significantly less nausea and vomiting.