Hundreds of patients have reported waking up during surgery, new research has revealed.
About 300 people in the UK say they have become conscious during surgery, known as "accidental awareness", after being put under general anaesthetic.
Every year there are around three million operations conducted in the UK where the patient is put under general anaesthesia, the Royal College of Anaesthetists (RCoA) said.
Their research suggest some level of accidental awareness occurs in one in every 19,000 operations, meaning each year there could be as many as 158 patients whose anaesthetic fails to work properly.
Surgeries such as cardiothoracic operations and caesarean sections seemed to carry a higher risk than others. However, the authors found the most "compelling risk factor" was the use of muscle relaxants, used to prevent the patient moving".
The majority of failures occur before surgery starts or after it finishes.
Just over half of those who reported feeling aware during surgery said the incident had caused them distress. Forty-one per cent reported suffering 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. Some patients described feelings of dissociation, panic, fear, suffocation and even dying, the authors said.
The report's authors made a series of recommendations, including the introduction of a simple anaesthesia check list which should be performed at the start of every operation.
"We found that patients are at higher risk of experiencing accidental awareness during general anaesthesia (AAGA) 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."
Additional reporting by PAReuse content