Epidurals and spinal anaesthetics are much safer than previously realised, researchers have concluded after carrying out the first nationwide census of the procedures.

Women given an epidural while giving birth and children undergoing surgery are among the patients facing the lowest risk.

Researchers estimated the chances of women in labour suffering permanent harm from an epidural as, at the most pessimistic, one in 80,000, but perhaps as low as one in 300,000. Rates for children given the procedure during an operation were similar.

Even among the highest-risk patients, generally those who are already frail and elderly, the chances of permanent harm range from one in 6,000 to one in 12,000.

Researchers carrying out the census, the biggest ever carried out to calculate the risks of epidurals and spinal anaesthetics, estimated that the average risk ranged from one in 23,000 to one in 50,000.

Estimates in the past have varied wildly. Among the most recent attempts to calculate the risks was a British study that concluded that the chances of major damage were as high as one in 675. Some patients were so concerned that they refused to undergo the anaesthetic procedures.

Similarly, a study in the United States put the risk at one in 800, although two Scandinavian studies estimated the risk of serious damage as ranging from one in 20,000 to one in 30,000.

Tim Cook, a consultant anaesthetist at the Royal United Hospital, Bath, who led the project, said: “Across all the groups of patients we looked at, the results were reassuring. The estimates were considerably lower risk than the estimates that some people have bandied about in the past.

“It is likely that this study will become widely quoted as the definitive estimate of these rare but potentially catastrophic complications. It means we are able to inform patients with much greater clarity of what the risks are.”

While risks assessed as being as low as one in 6,000 can be intimidating for some patients, Dr Cook pointed out that epidurals have been shown to save lives as well as dull pain. Researchers last year found that a life was saved once in every 450 low-risk surgical operations involving an epidural.

Instances where death or injury resulted were analysed in detail by a panel, and in every case it was found that the complications were a result of the patient’s condition, rather than mistakes by the medical team.

In most cases where death or permanent injury resulted the patient was elderly. Dr Cook said: “The reason is likely to be that many of these patients are elderly with medical problems and that the process of having surgery itself increases risks. Major surgery leads to severe pain and may mean that an epidural has to stay in place for several days. Epidurals are generally only used for the biggest, most painful operations, and it is probably the least fit patients who have the most to gain from these techniques.

“What the project has shown is that many complications of epidurals occur after major surgery in elderly unhealthy patients. The risks must also be balanced against the generally accepted benefits of epidurals.”

He hopes that data from the study can be used to help to identify improvements to prevent complications. “Although complications related to epidurals are rare, the profession still needs to examine how and why these complications arise and make steps to reduce their frequency,” Dr Cook said. “For instance, it is likely that the number of complications could be further reduced by a greater appreciation that prolonged weakness of the legs after an epidural or spinal is not normal and should be investigated by an experienced doctor to ensure that a major complication is not developing.”

Pain relief

Epidurals are mainly used to:

- Control pain in childbirth
- Provide anaesthesia for surgery
- Control pain after surgery
- Treatment of chronic back pain and sciatica

An epidural anaesthetic blocks the nerve roots that lead to the uterus and lower part of the body, which are located in a space near the spinal cord called the epidural space

An epidural is an injection into the small of the back, using a curved, hollow needle

The needle goes between the vertebrae and into the space outside the coverings that surround the spinal cord

A fine tube is passed through the needle and then the needle is removed

An anaesthetist then injects a local anaesthetic into the tube, which numbs the lower part of the abdomen and legs and feet

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