At first, Barbara Tite thought she was dreaming as she heard the muffled voices of her surgeon and the anaesthetist around her hospital bed.
It was only when she felt hands moving inside her abdomen that a terrifying realisation struck.
Barbara had woken up on the operating table during surgery for a perforated bowel: unable to move and frightened, she could actually feel what was going on.
'At first I thought I'd come round and was in recovery,' she recalls.
'Then I could feel hands rummaging in my abdomen. There was no pain, just a sensation of the hands tugging inside me. I could also hear muffled laughter.
'I realised I was still being operated on, but they did not know I had woken up.'
Barbara, 69, a former teacher from Milton Keynes, adds: 'I wanted to scream but couldn't move my head or open my mouth. I couldn't do anything. It was horrendous, like being buried alive.'
Realising she needed to attract the attention of the surgical team, Barbara summoned up all her strength and tried to make a small movement. Somehow, she managed to wiggle her little finger - then felt someone touch it.
'Then I went under again and when I woke, I was in recovery,' says Barbara, whose husband Brian is her registered carer.
She has no idea how long she was awake for. 'It felt like ages, but could have been seconds.'
Waking up during an operation - known as 'anaesthesia awareness' - is one of the greatest anxieties for most patients: nearly three quarters (74 per cent) fear being aware during an operation, according to a 2010 study in the Saudi Journal of Anaesthesia.
The term is used to describe when a patient regains partial or full consciousness during surgery despite being under general anaesthesia - and may lead to hearing conversations, and feeling paralysed. Pain is uncommon, although some report feeling everything that is being done to them.
Most cases are a result of inadequate doses of anaesthetic.
As Jonathan Hardman, a professor of anaesthesia and perioperative medicine at Nottingham University, explains: 'This is often as a result of clinical error [such as an error setting up the intravenous drug infusions].'
General anaesthetic drugs work by interrupting the normal transmission between nerve cells in the brain, adds Dr Tim Meek, president of the Association of Anaesthetists. 'In doing so they prevent consciousness - and memories from being formed.'
He says that the doses of anaesthetic drugs 'required to send somebody to sleep and to keep them asleep is influenced by many things, including age and weight - the sensitivity of the brain varies with age'.
He adds: 'As a general oversimplification, younger people tend to need a higher dose of anaesthetic, and older people a lower dose. Heavier patients tend to need a higher dose of many drugs, too, simply because the dose is calculated on a "per kilogram" basis.'
'The dose may also have to be modified to take account of factors such as frailty, trauma or critical illness.'
Anaesthetists constantly monitor both the levels of anaesthetic in the body and its effects on the brain throughout the operation, so they can quickly make adjustments when they are needed, explains Dr Meek. 'We also monitor heart rate, blood pressure, breathing - changes in these could alert the anaesthetist to the possibility that awareness could be imminent,' he adds.
'Taking these things together, the potential for anaesthesia awareness is usually avoided.'
Some types of surgery carry a significantly higher risk of anaesthesia awareness, says Professor Hardman.
These include caesareans - where the dosing is limited in order to protect the baby from post-birth sedation.
There may also be a limit to the anaesthetic doses given for emergency surgery and critically ill patients. 'Light' anaesthesia is administered to protect them from cardiovascular collapse, a life-threatening emergency due to dangerously low blood pressure, where the heart cannot pump enough blood around the body.
Incidents of anaesthesia awareness are rare, occurring in one in 19,000 general anaesthetics
Barbara says the incident has left her 'very angry and am still traumatised'
Incidents of anaesthesia awareness are rare though, occurring in one in 19,000 general anaesthetics, according to a 2019 Royal College of Anaesthetists report.
However, a breakthrough in identifying potential markers for someone's consciousness could reduce the risk - and improve anaesthesia use generally.
Writing in the journal Nature recently, neuroscientists in China said they had found that general anaesthesia affected signals sent to the back of the brain (hitherto it's been thought the front of the brain is central to consciousness): the suggestion is that electrodes can be attached to a patient's forehead in future to tap into these signals and fine-tune the anaesthesia dose, and avoid over- or under-dosing.
After Barbara's surgery, the two anaesthetists involved came to see her - and the more junior medic apologised.
Barbara recalls: 'He held up his hands and said, "I'm so sorry - it was all my fault". It was only after the anaesthetic truly wore off that I felt angry. I had no follow-up. Just that apology.'
Not wanting to 'ruin a young man's career', Barbara decided not to make a formal complaint - 'but I was very angry and am still traumatised', she says. Over the years, Barbara has had numerous operations and anaesthetics but had never previously had a problem.
She was involved in a car accident 24 years ago - caused by a drunk and drugged driver - which left her with multiple burns, broken bones and post-traumatic stress disorder (PTSD). Then, in 2017, she was diagnosed with multiple myeloma, a rare cancer of the blood and bone and was given a stem cell transplant.
Doctors discovered a perforation in her bowel in 2024 - this can be life-threatening as it can allow bacteria and faeces to leak into the abdominal cavity, and she was rushed into theatre for a five-hour emergency operation.
The anaesthetic seemed to begin as normal, with the anaesthetist administering the drugs through a cannula in her arm.
Barbara recalls: ‘He told me to count backwards from ten, as always, and I did.’
As surgeons set to work on her perforated bowel and repair a twisted hernia - removing the dead bowel tissue - Barbara woke up. ‘My eyes were closed, but I was on the operating table. I could hear the surgeons and other staff in the room chatting.’
Not surprisingly, the incident has taken its toll on Barbara, who was allowed home a few days after her operation, but experienced traumatic dreams.
But when she mentioned this to her colorectal consultant, he said he’d never come across anaesthesia awareness - ‘he suggested I’d imagined the whole thing. I was furious and burst into tears and left,’ Barbara recalls.
She is currently undergoing chemotherapy to treat her myeloma and finally received therapy for PTSD after a Macmillan nurse intervened to help.
Barbara has the following words of advice: 'I don't want to scare anyone, but people should be aware that anaesthesia awareness is possible.
'Doctors should also be aware that their patients can and do wake up during surgery - and to admit when it happens and give them the help and support they need.'