Inadequate pain relief with labor epidurals: a multivariate analysis of associated factors

Labor epidural analgesia providing inadequate pain relief may cause maternal dissatisfaction and may fail to produce effective anesthesia when topped up for operative delivery. This study looked at factors associated with inadequate labor epidural analgesia.

Data were prospectively collected from 275 parturients receiving labor epidural analgesia. Pain was assessed 30 min after epidural insertion using a verbal pain scale of 0 to 100. A score of 10 or more was considered to represent inadequate pain relief. Sixteen factors chosen by experienced obstetric anesthesiologists for their association with inadequate labor epidural analgesia were studied.

Fifteen parturients were excluded. Forty-four of the remainder (16.9%) experienced inadequate pain relief. Multiparity, history of a previous failure of epidural analgesia, the use of air for loss of resistance, cervical dilatation >7 cm at insertion all had a statistically significant association with inadequate epidural analgesia (P<0.05). Logistic regression showed that cervical dilatation >7 cm, a history of opioid tolerance, a previous failed epidural and insertion of the epidural by a trainee anesthesiologist increased the odds ratio for inadequate pain relief.

The final model correctly classified 93% of the epidurals that provided effective analgesia but classified only 9.3% of those providing inadequate pain relief. This information can be used to develop a predictive score and change practice resulting in fewer inadequate epidurals.