Surgery problems caused by muscle-relaxing drug: Patients used to be over-anaesthetised, but are now so lightly sedated they risk waking up during an operation. Celia Hall reports

NORMAN DALTON, 55, from Leeds, who received pounds 9,000 in compensation because he was awake during a seven-hour heart bypass operation (report, front page) is a modern victim of a situation which first arose 50 years ago with the introduction of the muscle-relaxing drug, curare.

Until then, said Dr Gareth Jones, Professor of Anaesthesia at Addenbrooke's Hospital in Cambridge, patients were more likely to ask before the operation if they would ever wake up at the end of it. 'It is now quite commonplace for, say, one out of six patients to ask if they will wake up during their surgery. Certainly people today are much more aware of the possibility,' he said.

Professor Jones said that until the Second World War, people were given so much anaesthetic to achieve muscle relaxation that they risked respiratory failure and death. 'Muscle-relaxing drugs are necessary to stop reflex action. You want the patient landing on the floor and to enable the surgeon to get inside. The muscles need to be relaxed to do this.'

The problem is that when the muscles are relaxed, the patient is in effect paralysed and unable to speak or signal that he or she has woken.

When curare began to be used, a lower dose of anaesthetic was necessary. 'We have moved from the position of people being so heavily sedated that they died, to being so lightly sedated that they wake up,' he said.

He estimated that about 1 in 10,000 patients given general anaesthetic is 'wide awake and feels pain'. Perhaps 3 in 1,000 do not experience pain but have some recollection, and might say afterwards that they remembered 'feeling something pulling'.

Professor Jones said: 'It is a problem and quite a lot of research is being undertaken. In 150 years of anaesthesia we still do not have a single gadget to tell if the patient is conscious or not.' In his department, work was in progress to develop a brain-signal processing system to measure levels of consciousness. Research in Hull has involved cuffing the arm to prevent the relaxant affecting it, so that the patient can signal to the surgeons.

Some of these patients had indicated consciousness and pain during their operations but had no recollection of it afterwards.