The largest ever prospective study into the major complications of epidurals and spinal anaesthetics published in the British Journal of Anaesthesia concludes that previous studies have over-estimated the risks of severe complications of these procedures.
The study concludes that the estimated risk of permanent harm following a spinal anaesthetic or epidural is lower than 1 in 20,000 and in many circumstances the estimated risk is considerably lower.
The study finds that the risk of permanent injury (of whatever severity) is about 1 in 23-50,000. In betting terms, the odds of being badly injured by an epidural or spinal anaesthetic are considerably better than 20,000-to-1 against. The risk of being paralysed by one of these injections is 2-3 times rarer than of suffering any permanent harm. The risk for women requiring pain relief for labour or Caesarean section is lower still, the most pessimistic estimate of permanent harm is 1 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 also finds that the risk of harm when an epidural is used for surgery is considerably higher than the estimated risk of using it during childbirth: between 1 in 6,000 and 1 in 12,000. However, while these figures may appear high, they too are still considerably lower than many previous estimates, and Dr Tim Cook, a consultant anaesthetist at the Royal United Hospital, Bath who led the project believes there are other reasons to explain these figures: "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. The risks must also be balanced against the generally accepted benefits of epidurals."