Wilson MJA, et al. - Researchers performed an open-label, multicentre, randomised controlled trial in 14 UK maternity units to assess epidural analgesia progression among women using remifentanil patient-controlled analgesia (PCA) compared with pethidine. Compared with intramuscular pethidine, intravenous remifentanil PCA halved the proportion of epidural conversions. The results obtained from the study challenges routine pethidine use as a standard of care in labour.

Methods

• Participants in the study were women aged 16 years or older, beyond 37 weeks' gestation, in labour with a singleton cephalic presentation, and who requested opioid pain relief.
• Eligible study participants (1:1) were randomly assigned to either the intravenous remifentanil PCA group (40 μg bolus on demand with a 2 min lockout) or the intramuscular pethidine group (100 mg every 4 h, up to 400 mg in 24 h), using a web-based or telephone randomisation service with a minimisation algorithm for parity, maternal age, ethnicity, and mode of labour onset.
• Study participants and health-care providers were not masked to the group allocation because of the differences in routes of drug administration.
• The proportion of women who received epidural analgesia after enrolment for pain relief in labour was the primary outcome.  
• Primary analyses were unadjusted and analyzed by the intention-to-treat principle.

Results

• Two hundred one women were randomly assigned to the remifentanil PCA group and 200 to the pethidine group between May 13, 2014, and Sept 2, 2016.
• It was noted that one study participant in the pethidine group withdrew consent, leaving 199 for analyses.
• The findings demonstrated that the proportions of epidural conversion were 19% (39 of 201) in the remifentanil PCA group and 41% (81 of 199) in the pethidine group (risk ratio 0·48, 95% CI 0·34–0·66; p < 0·0001).
• No serious adverse events or drug reactions directly attributable to either analgesic during the study were noted.