One in 10 People Conscious Under Anesthesia, Half of Them Can Feel Pain

Around 1 in 10 surgery patients studied by researchers were still partly conscious during their procedure despite having been given general anesthesia, a study has suggested.

The study involved 338 patients aged between 18 to 40 and 10 hospitals across the world. Its purpose was to investigate a medical phenomenon known as connected consciousness, which in the field of anesthetics refers to a patient being somewhat aware of what's happening around them while under general anesthesia.

Previously the phenomenon, which can happen for varying lengths of time, was thought to occur in around 5 percent of patients.

Patient asleep
A stock photo depicts a patient apparently under anesthesia wearing a mask. About 11 percent of people assessed as part of a study were reported to be somewhat responsive after being given general anesthesia. Wavebreakmedia/Getty

The new study, which involved 29 researchers from various institutions, concluded the figure could be more than double that at 11 percent—based on their findings, at least.

To start, the researchers collected study participants who were due to go under general anesthetic along with a tracheal intubation procedure, in which a tube is inserted into the windpipe to give the patient oxygen, medicine or anesthesia.

Once the patients were under general anesthetic and had their tracheal tubes inserted, the researchers asked them a series of questions to test whether they would respond. The questions were asked alongside commands such as "squeeze my hand" and "squeeze my hand twice if you are experiencing pain."

They found that 37 of the subjects did respond and that women were three times more likely to respond than men were. Of the people who responded, half were able to communicate that they were experiencing pain.

The patients generally were more likely to respond if they were given a command rather than a nonsense statement.

However, after the patients' surgeries went ahead, none of them said they could remember being given the commands. A notable exception was one patient who said they were able to recall the experience of surgery.

Robert Sanders, Nuffield Chair of Anesthetics at the University of Sydney in Australia and senior author of the study, told Newsweek:

"Our data suggests that in about 1 in 10 young adult patients may have experiences after being intubated during general anaesthesia. Half of these patients may have pain—approximately 1 in 20—but patients do not remember these events afterwards. These events were also more common in females.

"While these events may be concerning for patients, we show that with continuous titration of anaesthesia prior to intubation we can reduce that risk.

"We suggest clinicians consider this practice, if its not already their routine approach. Patients with concerns should talk directly with their anesthetist. Anesthetists are highly trained doctors and we welcome the opportunity to discuss these issues with patients to help allay those concerns."

Sanders also said in a university press release that the goal of the study "is not to discourage people from surgeries under general anesthetic—it is very important to note that patients did not remember responding to the commands."

"This research also highlights the need to better understand how different people respond to the anesthesia medication. There is an urgent need for further research on the biological differences, particularly sex, that may influence sensitivity to anesthetic medication."

The study was published in the British Journal of Anaesthesia on May 23 this year.

There have been some reports of people being awake during surgery, though the American Society of Anesthesiologists states on its website that surgery and anesthesia "are safer today than ever before."