Comparison of remifentanil: Entonox with Entonox alone in labor analgesia

Background: We designed a study to evaluate the effectiveness of continuous low dose infusion of remifentanil adding to self-administration of entonox administered for pain relief during the active phase of first stage of labor.
Materials and Methods: Thirty healthy term pregnant women recruited in our randomized double-blind, cross over study. They received the study medicines during two 30-min periods with a 15-min wash-out sequence after each period. Fifteen parturient used remifentanil as a single bolus dose followed by constant low dose infusion and self-administration of entonox (group R) during the first period and entonox and saline (group P) during the second period, while the remainder of the parturient used the drugs in a reverse order. Pain and Ramsay score, maternal and fetal hemodynamic, and ventilation were assessed during each intervention.
Results: In this study, mean pain severity scores were 8 ± 0.9 before and 5.4 ± 1.7 after intervention in group P, and 7.8 ± 0.1, 3.5 ± 1.3 in group R, respectively. Mean pain severity difference was 2.6 ± 1.5 in group P, while 4.3 ± 1.5 in group R; so, use of entonox and remifentanil can decrease labor pain two times more in comparison with entonox/placebo (normal saline). However, hemodynamic and ventilation parameter in remifentanil/entonox period were same as in entonox/placebo period. No statistical differences were seen in mean Ramsay score between group R and P. There was no episode of maternal bradycardia, hypotension, or hypoxemia.
Conclusion: Not only adding low dose infusion of remifentanil to self-administration of entonox was notable in labor pain reduction, it did n't make more parturient and neonatal side-effects.