(ORDO NEWS) — General anesthesia is a wonderful thing, knocking us out and blocking the feeling of pain in a matter of seconds before the operation.
But in rare cases, some people react to the environment under general anesthesia but cannot remember what happened next.
This phenomenon is called “connected consciousness” and now the largest study of this phenomenon to date shows that it is more common than first thought: it affects 1 in 10 young people, and more women than men.
The results highlight the need to better understand how different people respond to anesthetic drugs, the researchers say. Even after 170 years of using anesthesia, we still don’t know how general anesthesia works – and now age and gender seem to be another factor.
“There is an urgent need for further research into biological differences, especially gender, that may influence sensitivity to anesthetic drugs,” said study author Robert Sanders, an anesthesiologist and neurologist at the University of Sydney in Australia.
If the results of the new study can be replicated, it could take us one step closer to understanding who is more likely to experience “connected consciousness” and how anesthesiologists can reduce the likelihood of this.”
According to past estimates, about 5 percent of people undergoing general anesthesia experience “connected consciousness”. But Sanders’ team suspected, based on other research, that it might be more common in younger people.
Findings from a new study suggest that more young adults than expected are experiencing “connected consciousness” under general anesthesia prior to surgery.
Approximately one in ten of the 338 young people aged 18 to 40 who participated in the study responded to commands asking them to squeeze the researcher’s hand once if they understood and twice if they were in pain while 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 about the experience.
Women are two to three times more likely than men to experience “connected consciousness,” the study found.
The likelihood of “connected consciousness” was also lower if a continuous level of anesthesia was maintained for several minutes after the introduction of anesthesia and before intubation – the moment when a plastic tube is inserted into the person’s windpipe to maintain airflow and deliver anesthetic drugs during surgery.
It is important to note that “connected consciousness” is different from the involuntary awareness experienced by an even smaller proportion of people – just 0.1 percent – during anesthesia, after which they can remember specific details of the procedure.
“Connected” in this case refers to areas of the brain that are still able to process sensations from the environment, paying half attention, but not fully aware of them.
“Patients expect to be unconscious and pain-free under anesthesia, which shows why anesthesia research is so important,” says Sanders.
About 13 percent of women in the study responded to commands under anesthesia, compared to 6 percent of men, although they received the same weight-adjusted amount of propofol, a drug used to initiate and maintain general anesthesia.
“Differences in dosage, if present, were minor and do not explain why women experienced bound consciousness more often than men,” the researchers wrote in their paper.
About half of the 37 people who responded to the commands also indicated that they experienced pain that could be quickly resolved by adjusting the dose of anesthetic drugs. One person also clearly recalled the feeling of the operation after it was over.
“In our opinion, this is a higher level of consciousness than patients (or their anesthesiologists) expect during general anesthesia,” Sanders and colleagues write in their paper.
Although anesthetics may seem to knock us out with a bullet of drugs that enter the body before you can count to ten, being in a state of anesthesia only requires disconnecting the person from the environment, not necessarily involving complete loss of consciousness.
However, anesthesiologists seem to have to walk a very fine line, which can vary greatly from person to person.
At the very least, anesthesiologists can now better understand how maintaining continuous anesthesia for the first few minutes (already standard practice in many countries) can help reduce the “connected mind” frequency.
“It’s very important to note that the patients didn’t remember how they reacted to the commands,” Sanders says, noting that overall general anesthesia is very safe.
“It is also reassuring that if anesthetics are administered continuously between induction of anesthesia and intubation, the risk of associated consciousness is significantly reduced,” he says.
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