Esketamine administered epidurally as an adjuvant to epidural ropivacaine for labour analgesia: a prospective, double-blind dose-response study

Abstract

Objective To investigate the efficacy of esketamine as an adjuvant to epidural ropivacaine for labour analgesia by determining its effect on the median effective concentration (EC50) in a 20 ml volume of ropivacaine.Design A prospective, double-blind dose-response study.Setting This study was conducted in Women’s Hospital, School of Medicine, Zhejiang University, China.Participants One hundred and fifty parturients who requested epidural analgesia were recruited in this study to randomly receive epidural ropivacaine alone or with esketamine of 0.2 mg ml−1, 0.3 mg ml−1, 0.4 mg ml−1 or 0.5 mg ml−1, respectively.Primary and secondary outcome measures The primary outcome, EC50 of ropivacaine, was determined using an up-down sequential allocation technique. The secondary outcomes were analgesia characteristics, Ramsay Sedation Scale score, labour duration, caesarean section rate and adverse effects.Results The EC50 of ropivacaine with the addition of esketamine at concentrations of 0.3 mg ml−1, 0.4 mg ml−1 and 0.5 mg ml−1 resulted in significant reductions in the EC50 of ropivacaine to 0.050%, 0.044% and 0.043%, respectively, from baseline (esketamine 0 mg ml−1) (p<0.0001). However, reductions of the EC50 of ropivacaine were similar among the groups with esketamine of 0.3 mg ml−1, 0.4 mg ml−1 and 0.5 mg ml−1 (p>0.05). The Ramsay Sedation Scale score was higher and more dizziness was observed in the Group of esketamine 0.5 mg ml−1 compared with all other groups (p<0.0001). During the peripartum period, no differences in sensory blockade level, Bromage score, labour duration and percentage of caesarean delivery were found among the groups.Conclusions Under the conditions of this study, the addition of epidural esketamine of 0.3 mg⋅mL−1, 0.4 mg⋅mL−1 and 0.5 mg⋅mL−1 offered a similar ropivacaine dose-sparing effect; 0.5 mg⋅mL−1 of esketamine produced more adverse effects.Trial registration number ChiCTR2100054348.