Patients who heard themselves described as fat, ugly or overweight later complained when they recovered from the anaesthetic that had rendered them immobile and incapable of speech but not asleep.
A study of 45 patients who reported being conscious while undergoing major surgery found half said they were struck by the personal nature of remarks made about their bodies, the disease, or the surgery itself.
Half the patients said they were able to see what was going on with some able to recognise things or faces.
Two thirds recalled conversations and the same proportion felt being touched. But although most tried to alert someone, all found themselves to be paralysed and none succeeded.
The study, reported in the British Journal of Anaesthesia, is the latest to describe the rare event of awareness under a general anaesthetic. About one in 500 patients regains some level of consciousness during an operation but in almost every case they remain paralysed, unable to give any sign they are aware of what is going on.
Professor Dierk Schwender and colleagues of the Institute for Anaesthesiology, Munich, Germany, who found the patients by advertising for them, said that the feeling of helplessness was the most traumatic part of the experience for all of the patients.
"The feeling that they were unable to influence the situation was was more important than the pain some of them said they suffered," Professor Schwender said.
Although the cases are extremely rare, awareness under anaesthesia is commonest during caesarians, when doctors try to limit the amount of anaesthetic used to minimise the risk of harm to the baby, and during heart operations, when poor circulation means the anaesthetic may not reach the brain in sufficient quantities.
"We always prepare patients undergoing these operations and reassure them that we will talk to them all the time and watch out for any sign that they may be conscious. If you do that they are quite happy to accept it," Professor Schwender said. "One should treat patients always as patients, even when they are unconscious. It is when doctors fail to do that that problems occur."