Staying ‘conscious’ under anesthesia may be a lot more common than we thought

General anesthesia is a wonderful thing, knocking us out and blocking our sense of pain within seconds of surgery.

But in rare cases, some people react to their surroundings under general anesthesia, but they don’t remember what happened afterwards.

It’s called “wired consciousness,” and the largest such study to date into the phenomenon suggests it’s more common than previously thought, affecting 1 in 10 young adults, and women more than men.

The findings underscore the need to better understand how different people respond to anesthetic medications, the researchers say. Even after 170 years of use, we still don’t have a good understanding of how general anesthesia works – and now age and gender seem to be another factor in the mix.

“There is an urgent need for further research into biological differences, particularly sex, that may influence sensitivity to anesthetic drugs,” says study author Robert Sanders, an anesthetist and neuroscientist at the University of Sydney in Australia.

If the results of the new study can be replicated, it could bring us closer to understanding who is most likely to experience ‘connected consciousness’ and how anesthesiologists can reduce the chances of this happening.

Earlier estimates had suggested that about 5% of people undergoing general anesthesia had a “connected consciousness”. But Sanders’ team had suspected, based on other research, that it might have been more common among younger people.

The results of the new study suggest that more young adults than expected are still responsive under general anesthesia before surgery begins.

About one in 10 of the 338 young adults in the study, between the ages of 18 and 40, responded to commands asking them to shake hands with researchers once if they understood, and twice if they were in pain under general anesthesia.

One hour after waking up, participants were asked to recall 16 words they had heard under anesthesia, to see what they remembered from the experience.

According to the study, women were between two and three times more likely than men to experience “connected consciousness”.

The odds of “connected consciousness” were also lower if a continuous level of anesthesia was maintained within minutes of induction of anesthesia and prior to intubation, the point where a plastic tube is inserted into the windpipe. a person to maintain airflow and administer anesthetic drugs during surgery. .

Importantly, ‘connected awareness’ is different from the involuntary awareness that an even smaller fraction of people – only 0.1% – experience during anesthesia, after which they can recall specific details about the procedure.

“Connected” in this case refers to parts of the brain still able to process sensations from their surroundings, in half-attention but not fully aware.

“Patients expect to be unconscious under anesthesia and not in pain, and that shows why anesthesia research is so important,” says Sanders.

About 13% of women in the study responded to commands under anesthesia, compared to just 6% of men, even though they received the same weight-adjusted amounts of propofol, a drug used to start and maintain general anesthesia.

“Differences in dosage, if present, were small and do not explain why women experienced connected consciousness more often than men,” the researchers write in their paper.

About half of the 37 people who responded to the orders also indicated that they were in pain, which would have been quickly corrected by adjusting the dose of anesthetic drugs. One person also clearly recalled the experience of surgery after the procedure was completed.

“In our view, this is a higher level of consciousness than patients (or their anesthesiologists) anticipate during general anesthesia,” Sanders and colleagues write in the paper.

While it may feel like the anesthetics are knocking us out with a dose of the drug that hits before you can count to ten, being in a state of anesthesia only requires a person to be disconnected from their surroundings, not necessarily involving a total loss of consciousness. .

However, this clearly seems to be a very fine line for anesthesiologists, and one that seems to vary widely from person to person.

At least now anesthesiologists might have a better understanding of how maintaining continuous anesthesia in the first few minutes (which is already standard practice in many countries) can help reduce the incidence of “connected consciousness”. “.

“It’s very important to note that patients don’t remember responding to commands,” says Sanders, noting that overall, general anesthetics are very safe.

“It was also reassuring to see that if anesthetic drugs are continuously administered between induction of anesthesia and intubation, the risk of connected consciousness was significantly reduced,” he says.

The study was published in the British Journal of Anesthesia.

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