Risk factors of inadequate pain relief during epidural analgesia for labour and delivery

Purpose: To determine the causes of failure of epidural analgesia during labour and delivery. Methods: During six months, pregnant patients receiving:epidural analgesia and delivering vaginally were studied prospectively. Bupivacaine 0.125% was used for the initial bolus dose and subsequent continuous infusion. Top-ups of the same solution were used for inadequate pain relief assessed using a visual analogue pain score (VAPS) and/or by clinical examination. Inadequate pain relief was defined as the need for greater than or equal to 2 top-ups in addition to epidural infusion and failure during delivery as VAPS greater than or equal to 30 mm during the expulsion phase, Results: 1009 patients delivered during this period, 596 had epidural analgesia for vaginal delivery of a live infant and data were complete in 456. Inadequate pain relief during labour and during delivery were found in 5.3% and 19.7% of patients. Risk factors of inadequate pain relief included inadequate analgesic efficacy of the first dose (Odds ratio: 3.5, P = 0.001) and posterior presentation (Odds ratio: 5.6, P = 0.001). Radicular pain during epidural placement was associated with failure during labour (Odds ratio: 3.9, P = 0.05). Duration of epidural analgesia > six hours (Odds ratio: 9.1, P = 0.001) was a risk factor for insufficient pain relief during labour whereas duration of epidural analgesia < one hour was associated with pain during delivery (Odds ratio: 18.3, P = 0.001). Conclusion: Several obstetrical and epidural-related factors increase the risk of inadequate epidural;analgesia. For some, simple changes of practice pattern may lead to improved pain relief.