The Clinical Effective Concentration Of Ropivacaine Combined With Hydromorphone For Epidural Labor Analgesia

Objective: To determine the minimum local analgesic concentration(MLAC)and90% effective concentration(EC90)of ropivacaine combined with hydromorphone for epidural labor analgesia in the latent period by a modified Dixon’s up-and-down sequential allocation method.Methods: Thirty cases of single-fetal primiparous were selected in this study from June 2019 to January 2020,ASA physical status I or II,aged 20 to 35 years old,weight55 to 85 kg.All parturients entered the incubation period of the first stage of labor,chose L2-3 for epidural labor analgesia,10 ml ropivacaine mixed with 15μg/ml hydromorphone were injected.According to the modified sequential allocation method to increase or decrease the concentration of ropivacaine.The initial concentration of ropivacaine was0.07%,the concentration gradient is 0.01%,the next patient was decided to increase or decrease a gradient based on the analgesia efficacy of the previous patient.Using visual analogue scale(VAS)pain score to determine whether analgesia was effective.After 30 minutes of administration,if VAS≤3,the analgesia was effective,the next patient would be reduced a concentration gradient,if VAS>3,after giving 6ml of dose 0.1% ropivacaine mixed with 0.5μg/ml sufentanil to remedy,VAS≤3,the analgesia was ineffective,the following one patient would be increased a concentration gradient;if after giving remedy drugs VAS>3,the analgesia was failed,this case would be eliminated,and the next patient would be repeated this concentration.The MLAC and EC90 of ropivacaine corresponding95% confidence intervals(CI)were calculated by probability unit regression analysis.The VAS pain score,Bromage motor block score,block level of epidural anesthesia,fetal heart rate,blood pressure,heart rate,respiration,peripheral oxygen saturation before injection(T0),5min(T1),15min(T2),30min(T3)after injection were recorded.In addition,record the onset time of anesthesia,labor time,mode of delivery,cases of increased oxytocin using.The number of cases of fetal heart deceleration and the neonatal Apgar score at 1min,5 min after birth were evaluated and recorded.Adverse reactions such as nausea and vomiting,skin pruritus,chills,respiratory depression,hypotension and urinary retention during epidural analgesia were recorded.Results: The MLAC of ropivacaine combined with hydromorphone for epidural labor analgesia during the incubation period was 0.035%(95% CI 0.026% ～ 0.042%),and the EC90 was 0.049%(95% CI 0.042% ～ 0.082%).One puerpera had numbness in the lower limbs,and three puerperants were changed to cesarean section,without other adverse reactions.Conclusion: The MLAC and EC90 of ropivacaine combined with hydromorphone for epidural labor analgesia during the incubation period is 0.035%(95%CI0.026%～0.042%)and 0.049%(95%CI 0.042%～0.082%).Hydromorphone can be safely used for epidural labor analgesia,rapid onset and fewer adverse reactions.