4. Discussion
NRS
Our study showed that in DPEA, the onset time of anesthesia was shorter when the experimental dose was injected directly through the epidural puncture needle and the analgesic effect was better when the test dose was injected after inserting the epidural catheter. In DPEA, when the drug was injected after catheterization, there was no significant difference between DPEA and EA with respect to the analgesic effect.The onset time of analgesia in the DPE2 group was shorter than in the EA group, and the NRS score at T1 and T4 was significantly lower than in the EA group. This indicates that the drug diffused into the subarachnoid space when the experimental dose was injected through the epidural puncture needle, which was responsible for the subarachnoid anesthesia. There was no significant difference in the analgesic effect between DPE1 and EA groups. This indicates that the drug did not diffuse into the subarachnoid space, or the amount of diffused drug was significantly smaller when the drug was injected after the epidural catheter was placed, and therefore the effect of subarachnoid anesthesia was minimal. This might be related to the position and direction of drug injection. In this study, the position of drug delivery in the DPE2 group was anterior to the dural hole, whereas that in the DPE1 group was anterosuperior to the dural hole. Thus, the drug delivery in the DPE2 group was closer to the dural hole than in the DPE1 group. Hence, it could easily spread to the subarachnoid space. When the epidural catheter was used for drug delivery, the drug diffused from multiple directions because the catheter had 3-sided holes. When the drug was injected directly from the epidural puncture needle, the entire drug volume diffused anterior to the dural hole. Hence, the probability of drug diffusion into the subarachnoid space in the DPE2 group was higher than in the DPE1 group.Gupta et alContreras et alA study of Chau et alThis study had several limitations. First, the maternal satisfaction was not assessed in the present study. The NRS score showed that parturients in 3 groups achieved sufficient analgesia 30 minutes after anesthesia, but whether the parturients were satisfied with the overall anesthetic effect was still unclear. Second, the time points at which NRS score was obtained were scattered and should be more concentrated. In our study, NRS score was obtained at 5 time points, in which T3 and T4 were at the second stage of labor and the time of vaginal suture, respectively. The time of the first stage of labor was different among parturients. Hence, the time of T3 and T4 from the time of implementation of anesthesia was different, which could lead to deviations in NRS scores at T3 and T4. Third, after anesthesia, the anesthesia level was not confirmed. Asymmetry of bilateral block areas was not found. Fourth, the times of patient-controlled analgesia were not recorded in these parturients. Thus, it is infeasible to assess the difference in the total dose used in 3 groups.