Abstract:

Objective To investigate the effects of varying pulse intervals in the programmed intermittent epidural bolus （PIEB） mode on labor analgesia in primiparous and multiparous women， and to evaluate the differences in analgesic outcomes between these two groups. Methods A total of 60 primiparous and 60 multiparous women who met the inclusion criteria were recruited and randomly allocated into two groups： a 45?minute pulse interval group （P45 group， n = 30） and a 60?minute pulse interval group （P60 group， n = 30）. Epidural labor analgesia was initiated when cervical dilation reached 1 ~ 3 cm. The programmed intermittent epidural bolus （PIEB） mode was started 45 minutes after analgesia commencement in the P45 group and 60 minutes after analgesia commencement in the P60 group. Each pulse delivered 10 ml of a solution containing 0.08% ropivacaine and 0.5 μg/ml sufentanil. Pain scores were assessed using the Visual Analog Scale （VAS） at five specific time points： baseline （t0）， 1 hour post?analgesia initiation （t1）， 2 hours post?analgesia initiation （t2）， full cervical dilation （t3）， and delivery （t4）. Secondary outcomes included Bromage scores， the number of patient?controlled analgesia （PCA） button presses， total drug consumption， and adverse reactions. Results In primiparous women， the VAS score at t1 was significantly lower in the P45 group compared to the P60 group （P < 0.05）， whereas no significant differences were observed in VAS scores between the two groups at t2—t4. The median PCA press count was also significantly lower in the P45 group than in the P60 group （P < 0.05）. However， there were no significant differences between the groups in terms of total drug consumption， Bromage scores， or the incidence of adverse events （P > 0.05）. In multiparous women， no significant differences were found in VAS scores， Bromage scores， or PCA press counts between the P45 and P60 groups at any time point （P > 0.05）. Conversely， total drug consumption was significantly higher in the P45 group compared to the P60 group （P < 0.05）. Conclusions For primiparous women， a 45?minute pulse interval in the PIEB mode not only provides superior labor analgesia but also significantly reduces the frequency of PCA presses without escalating the risk or severity of motor block or adverse events. For multiparous women， the pulse interval does not substantially influence the effectiveness of labor analgesia. These findings contribute valuable new evidence for refining clinical labor analgesia protocols.

Key words: nulliparous women, multiparous women, programmed intermittent epidural bolus, pulse interval time