Risk of complications from epidural anaesthetics much lower than thought

Published on Monday 12 January 2009 19:11

Previous analyses have over-estimated the risks of severe complications from these procedures, the research found.

The study concludes that the estimated risk of permanent harm following a spinal anaesthetic or epidural is lower than one in 20,000, and in many circumstances considerably lower.

The research, published in the British Journal of Anaesthesia, found the risk of permanent injury – defined as symptoms lasting more than six months – was about one in 23,000 to one in 50,000.

The risk of being paralysed by one of these injections is two to three times rarer than of suffering any permanent harm, and the risk for women requiring pain relief for labour or Caesarean section is lower still, with the most pessimistic estimate of permanent harm being one in 80,000, and it may be much lower.

A similarly low risk was found in procedures performed for chronic pain and in children.

The study found that the risk of harm when an epidural was used for surgery is considerably higher than the estimated risk of using it during childbirth – between one in 6,000 and one in 12,000. However, these figures are also considerably lower than many previous estimates.

Dr Tim Cook, a consultant anaesthetist at the Royal United Hospital, Bath, who led the project, said: "It has been known for a long time that these complications occur more often after surgery.

"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," said Dr Cook. "The risks must also be balanced against the generally accepted benefits of epidurals."

The project's results are based on the voluntary participation of every hospital in England, Scotland, Wales and Northern Ireland. A national census identified more than 700,000 spinals and epidurals performed in the NHS each year.

All major complications of these procedures were identified for one year.

Most complications were judged to be unavoidable. Dr Cook said: "The results are reassuring for patients, with all procedures and settings being lower-risk than many previous estimates. It is likely that this study will become widely quoted as the definitive estimate of these rare, but potentially catastrophic, complications."

But he added: "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.

"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 a major complication is not developing."

Major complications of spinals and epidurals include damage to nerves or the spinal cord by infection (meningitis and abscess), bleeding and blood clots (haematoma), direct damage to the nerves (needle injury or chemical injury) and poor blood supply to the spinal cord (ischaemia). All can cause permanent nerve injury, including paralysis.