More than 150 UK patients could wake up every year while undergoing surgery, figures suggest.

Around one patient in every 19,000 spontaneously reports “accidental awareness” after being put under general anaesthetic, new research suggests.

Every year there are around three million operations conducted in the UK in which the patient is put under general anaesthesia, the Royal College of Anaesthetists said.

This means that each year there could be as many as 158 patients whose anaesthetic fails to work properly.

The college said that accidental awareness is one of the “most feared” complications of general anaesthesia for both patients and doctors. It occurs when general anaesthesia is intended but the patient remains conscious.

A new report from the Royal College and the Association of Anaesthetists of Great Britain and Ireland studied three million operations conducted in public hospitals in the UK and Ireland - including 300 reports of awareness.

The authors found that some surgeries - such as cardiothoracic operations and caesarean sections - carry a higher risk than others and people who have been given muscle relaxants are also more likely to suffer this complication.

They said the majority of anaesthetic failures occur before surgery starts or after it finishes.

But 51 per cent of those who spontaneously reported the failure said the incident had caused them distress and 41 per cent suffered longer-term psychological harm such as post-traumatic stress disorder, the authors said.

Sensations experienced when accidentally aware included tugging, stitching, pain, paralysis and choking, they found.

And patients described feelings of dissociation, panic, fear, suffocation and even dying, the authors said.

They made a series of recommendations, including the introduction of a simple anaesthesia check list which should be performed at the start of every operation. They also called for a structured approach to the management of patients who report awareness.

“We found that patients are at higher risk of experiencing accidental awareness during general anaesthesia during caesarean section and cardiothoracic surgery, if they are obese or when there is difficulty managing the airway at the start of anaesthesia,” said project lead professor Jaideep Pandit, a consultant anaesthetist in Oxford.

“The use of some emergency drugs heightens risk, as does the use of certain anaesthetic techniques. However, the most compelling risk factor is the use of muscle relaxants, which prevent the patient moving.”