Choice of opioid for initiation of combined spinal epidural analgesia in labour - fentanyl or diamorphine

Sixty-two women requesting regional analgesia in labour were allocated to receive a 1.5 mi intrathecal injection as part of a combined spinal-epidural (CSE) analgesic technique. This contained either bupivacaine 2.5 mg plus fentanyl 25 mug (group F) or bupivacaine 2.5 mg plus diamorphine 250 mug (group D). Times of analgesic onset and offset were (r)ecorded, motor and proprioceptive assessments made and side-effects noted. Analgesic onset was not significantly different between the groups (group F, 8.0 min; group D, 9.5 min; P=0.3) but time to first top-up request was significantly longer in the diamorphine group (group F, 73 min; group D, 101 min; P=0.003), Motor loss, assessed by the modified Bromage score, was statistically but not clinically greater in the fentanyl group (P=0.01). Maternal hypotension, pruritis, proprioceptive loss, nausea and fetal bradycardia were rare and not severe, and their incidences did not differ between groups. No respiratory depression was observed after CSE. This use of diamorphine was not associated with increased side-effects compared with fentanyl/bupivacaine, and it has a longer duration of action.