Women who were given intravenous remifentanil patient-controlled analgesia (PCA) in labour were half as likely to have an epidural compared to women given intramuscular pethidine, reports a study in the Lancet.
About a third of women receiving the commonly used analgesic pethidine for labour pain subsequently require an epidural, increasing the risk of instrumental vaginal delivery.
The open-label, multicentre, randomised controlled RESPITE trial in 14 UK maternity units assigned eligible participants (1:1) to either intravenous remifentanil PCA (40μg bolus on demand with a two-minute lockout) or intramuscular pethidine (100mg every four hours, up to 400mg in 24 hours).
The proportions of epidural conversion were 19 per cent (39/201) in the remifentanil PCA group and 41 per cent (81/199) in the pethidine group (risk ratio 0.48; 95% CI 0.34-0.66: P<.0001>
Women receiving remifentanil reported lower pain scores and were more likely to have a spontaneous vaginal delivery than those receiving pethidine, with the difference in delivery mode attributable to a reduction in instrumental vaginal delivery.
There were no serious adverse events or drug reactions directly attributable to either analgesic during the study.
The findings challenge routine pethidine use as standard of care in labour, said the authors.