Labor epidural analgesia onset time and subsequent analgesic requirements

Background

We investigated the correlation between lumbar epidural analgesia onset time and pain intensity at 60 and 120 min after initiation.

Methods

We conducted a prospective observational study of nulliparous women receiving lumbar epidural analgesia (initial bolus 15 mL bupivacaine 0.1% with fentanyl 3.33 μg/mL), followed by patient-controlled epidural analgesia (PCEA). The measured variable was lumbar epidural analgesia onset time (time to pain numerical rating score ≤3). Secondary outcomes were pain score at 60 and 120 min and at full dilatation; and analgesic requirements through the labor.

Results

One-hundred-and-five women were eligible for analysis. There was a significant correlation between lumbar epidural analgesia onset time and pain intensity at 60 min (Spearman’s R²=0.286, P=0.003), but not at 120 min (R²=0.030, P=0.76). Women who requested more PCEA boluses during the first 120 min had a longer lumbar epidural analgesia onset time (R²=0.321, P=0.001) and reported higher pain scores at 60 min (R²=0.588, P <0.001) and at 120 min (R²=0.539, P <0.001). Women who reported higher pain scores at 60 min had more pain at 120 min (R²=0.47, P <0.001) and higher analgesic consumption during labor (R²=0.403, P <0.001). Women who were at a greater cervical dilatation at 60 and 120 min had higher pain scores at the same time point (R²=0.259, P=0.008 and R²=0.243, P=0.013 respectively).

Conclusion

There was a correlation between the onset time of lumbar epidural analgesia during labor and the pain score 60 min later but this had disappeared by 120 min.