Low-Frequency Peripheral Nerve And Muscle Stimulator Combined With Phloroglucinol Reduce Labor Pain: A Randomised Trial

Objective: To explore the analgesic effect and safety of low-frequency peripheral nerve and muscle stimulator combined with phloroglucinol on labor pain based on pain scoring,plasma dynorphin level and labor stages,2 hours' postpartum hemorrhage,neonatal apgar score,and surgical percentage.Methods: 140 primiparas in accordance with the inclusion criteria were recruited and randomly divided into four experimental groups: Group 1(Low-frequency peripheral nerve and muscle stimulator+phloroglucinol group),Group 2(low-frequency peripheral nerve and muscle stimulator group),Group 3(phloroglucinol group),Group 4(control group),each with 35 subjects.Intervention began while the cervical dilatation?3cm,and VAS(visual analogue scale)was used to assess pain: before intervention,60 minutes after intervention,cervical dilatation=7-8cm,and full cervical dilatation,the VAS scores were recorded as the primary objective of this study.A reduction of 3 and more of VAS score after intervention was considered positive effect.5 ml blood was taken from anconeal median venous before intervention and 60 minutes after intervention as sample to measure the Dynorphin levels by ELISA.Meantime,dynorphin concentration,labor stages,2 hours' postpartum hemorrhage,neonatal Apgar score,delivery mode were recorded as the secondary objective of this study.All data were analyzed by SPSS 24.0 and P<0.05 considered to be statistically significant.Results:1.Analgesic effect(1)Comparison of VAS scores in four groups,there was no significant difference in VAS scores before intervention(P>0.05).However,after intervention,in different times,significant differences in VAS scores were found in different groups(P<0.05).(2)Comparison of VAS scores in different times,in each group,significant differences were found in different times(P<0.05).(3)Percentage of analgesic positive effect,positive effect,i.e.VAS score reduction?3 was reported by 85.7% subjects in group 1,62.9% in group 2,0% in group 3,0% in group 4.There was a significant difference between group 1 and group 2(P<0.05).2.Plasma dynorphin levelsThe dynorphin levels increased after intervention,with significant differences between before intervention and after intervention indicated in group 1 and group 2(P<0.05).There was no significant difference in group 3 and group 4(P>0.05).3.Stage of laborThere was a significant difference in four groups in the active phase of the first stage after intervention(P=0.017<0.05),and no significant difference in the second and the third stage of labor in four groups(P>0.05).4.Delivery outcomesThere was no significant difference in 2 hours' postpartum hemorrhage,neonatal Apgar score and surgical percentage in four groups(P>0.05).Conclusions: The study revealed that,1.Low-frequency peripheral nerve and muscle stimulator conbined with phloroglucinol resulted in a significant decrease of VAS scores,an increased dynorphin levels and an increased analgesic effect,i.e.,labor pain reduced.2.Low-frequency peripheral nerve and muscle stimulator combined with phloroglucinol resulted in a shorter active phase of the first stage but no effects on the second or the third stage.3.Low-frequency peripheral nerve and muscle stimulator combined with phloroglucinol for labor pain management had no effects on 2 hours' postpartum hemorrhage,neonatal Apgar score and surgical percentage.4.Low frequency peripheral nerve and muscle stimulator could significantly increase the endogenous dynorphin levels but reduce The VAS scores and the active phase of the first stage.5.Phloroglucinol resulted in a shorter active phase of the first stage,but did little to reduce The VAS scores and had no effects on dynorphin levels.