“I wonder if you can help us find up-to-date data on how likely an epidural is to be successful? Woman sometimes ask about this because a friend had a failed epidural, and the figures that we have found are quite variable.”
This is one of those questions where I feel I need to give you the boring caveats which explain why it’s hard to answer (and perhaps why those figures are variable) first. But I will then try to give you a half-decent answer.
It is hard to answer this question definitively for a few reasons.
1. Success rates differ quite a bit between people and places and studies, and even between the same anaesthetist at different times, so we are not going to be able to pinpoint an exact and universal number. Siting an epidural is a complex human task. And it’s performed on a sometimes moving target. The variables that affect success are not just to do with the anaesthetist, the setting or the equipment, but some are also to do with the individual woman. These include body shape and size, and the ability to get and stay in certain positions, which is not always easy when one is in labour.
2. Because pain and pain relief are subjective and people have different expectations, the definition of ‘success’ will vary between people, including researchers. To put it into research terms, there is no universal outcome measure for this. Does an epidural have to remove every last smidgen of sensation to be successful, or is it still a success if it removes 90 per cent of pain? Does it matter how the woman feels? How about if it removes half the pain but she’s delighted? What if it is successful for the first hour but then the catheter moves and it no longer works? There are some big questions here about what constitutes success when it comes to epidurals.
So, with those points in mind, let’s look for the figures…
One of the more obvious places to start is the Cochrane review which compared epidural with non-epidural or no analgesia in labour (Anim-Somuah et al 2011). This found that, compared to those other possibilities, epidural was more effective overall, although it did have downsides including increased length of second stage, increased need for oxytocin and increased likelihood of instrumental delivery. Unfortunately, though, because it was comparing epidural to other possibilities, the review did not specifically focus on success or failure rates of epidural in itself.
Luckily, a few other groups of researchers have specifically looked at this question. Some of the better examples include a (freely available) review by Hermanides et al (2012) which considered a number of studies of epidural, not just in childbirth, and concluded that the overall failure rate was around 30%. This isn’t necessarily the most helpful figure though, because it doesn’t just apply to women in labour, but to all people having epidurals, which means a lot of people who are very ill and having surgery. Two retrospective studies that were included in that review did focus on evaluating epidurals in labouring women, and these found failure rates of 13.1% (Eappen et al 1988) and 14% (Pan et al 2004), although (as above) they each used different criteria for measuring success.
Those figures were challenged by a study by Thangamuthu et al (2013). In consultation with a group of consultant anaesthetists, they created a standardised definition. This addressed some of the problems mentioned above, although some uncertainty will always remain.Then, they used this to measure the epidural failure rate within a large UK hospital Trust. Their standardised tool used several means of measuring epidural success/failure which included asking women for their own assessment at a follow-up visit. This is a great idea, though it is interesting to note Thangamuthu et al’s (2013) concern: even women who have to have their epidurals resited several times sometimes still describe it as successful. An anaesthetist or midwife might not consider that to be successful.
Overall, the epidural failure rate in Thangamuthu et al’s research was 23%, which they acknowledge is at the upper end of published figures. But they also note that their standardised definition is being used in other hospitals with similar results. So far, this is the best research in this area that I have been able find.
More recently still, Guasch et al (2017) considered this area and noted that:
“Labor epidural failure is still not standardly defined, consequently its incidence is uncertain: improving the knowledge of risk factors related to failure will increase epidural block success rate. Prolonged labors, previous history of epidural failure, and repeated top-ups needed during labor are recognized risk factors for failure. Clinical experience and the use of modern equipment (ultrasound guided blocks), as well as the choice of neuraxial technique (epidural versus combined spinal-epidural) may affect failure rate. Software-controlled infusion pumps seem to increase epidural analgesia success rate. Among non-technical skills, good communication among medical team members and parturient women is another pivotal point to achieve a satisfactory analgesia for labor. Clear algorithms should be promoted where epidural failure during labor or caesarean delivery may occur.” Guasch et al (2017)
It is important to share some of the uncertainties and previous data in this area with women so that they can take this into account in their decision-making. But Thangamuthu et al’s (2013) epidural failure rate of up to 23% is the best data I can find on this topic at the moment.
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Anim-Somuah M, Smyth RMD, Jones L. Epidural versus non-epidural or no analgesia in labour. Cochrane Database of Systematic Reviews 2011, Issue 12. Art. No.: CD000331. DOI: 10.1002/14651858.CD000331.pub3.
Eappen S, Blinn A, Segal S (1998). Incidence of epidural catheter re-placement in parturients: a retrospective chart review. International Journal of Obstetric Anesthesia 7: 220–5.
Pan PH, Bogard TD, Owen MD (2004). Incidence and characteristics of failures in obstetric neuraxial analgesia and anesthesia: a retro-spective analysis of 19,259 deliveries. International Journal of Obstetric Anesthesia 13: 227–33
Thangamuthu A, Russell IF and Purva M (2013). Epidural failure rate using a standardised definition. International Journal of Obstetric Anesthesia 22(4):310-315