Staying 'Conscious' Under Anesthesia May Be Much More Common Than We Realized

Before surgery, general anesthetic works wonders, knocking us out and eliminating our perception of pain in a couple of seconds.

However, in a small number of cases, patients are aware of their surroundings while under general anesthesia, but they have no recollection of what transpired afterwards.

This is known as 'connected awareness,' and the greatest research of its sort to date on the phenomenon reveals that it is more widespread than previously assumed, impacting one out of every ten young adults, with women experiencing it more than males.

The findings underscore the need of learning more about how various people react to anesthetic medicines, according to the researchers. We still don't have a good understanding of how general anesthetic works, even after 170 years of usage — and now age and sex appear to be added to the mix.

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

If the current study's findings can be duplicated, we'll be one step closer to figuring out who is more prone to have 'connected consciousness,' and how anesthesiologists may lower the chances of it happening.

Around 5% of persons undergoing general anesthesia, according to previous estimates, experienced 'connected awareness.' However, Sanders' team assumed it was more frequent in younger individuals based on earlier findings.

According to the findings of the current study, a higher percentage of young persons are still responsive under general anesthesia before surgery than previously thought.

While under general anesthesia, around one in ten of the 338 young people in the study, aged 18 to 40, reacted to directions to grip the researchers' hand once if they understood and twice if they were in pain.

Participants were asked to recollect 16 sentences they had heard under anesthesia an hour after waking up to see what they recalled of the event.

The study discovered that women were two to three times more likely than males to experience 'connected consciousness.'

If a continuous level of anesthesia was maintained in the minutes after anesthesia was induced and before intubation, the point where a plastic tube is inserted down a person's windpipe to maintain airflow and deliver anesthetic drugs during surgery, the chances of 'connected consciousness' were also lower.

It's vital to distinguish 'connected consciousness' from the unexpected awareness that a far smaller percentage of people – about 0.1 percent – experience after anesthesia and then recall precise facts about the surgery.

In this case, 'connected' refers to portions of the brain that are still capable of processing stimuli from their surroundings, half-conscious but not completely aware.

"Patients expect to be unconscious under anesthesia, and not be in pain, and this demonstrates why research into anesthesia is so important," Sanders adds.

Despite receiving the same weight-adjusted quantities of propofol, a medicine used to start and maintain general anesthesia, only 13 percent of women in the trial reacted to orders, compared to only 6 percent of males.

"Differences in dosing, if present, were small and do not explain why females experienced connected consciousness more often than males," the researchers conclude in their report.

Approximately half of the 37 patients who reacted to orders also stated that they were in pain, which might have been quickly alleviated by increasing the anesthetic medication dose. After the operation, one participant vividly remembered the surgical experience.

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

While it may appear that anesthetics knock us out with a slug-punch of medications that hits before you can count to ten, being in a state of anesthesia just needs a person to be isolated from their surroundings and does not always imply a complete loss of awareness.
However, it appears to be a very narrow line for anesthetists to walk, and one that varies dramatically from one individual to the next.

Anesthesiologists may now have a better grasp of how sustaining continuous anesthesia in the initial few minutes (which is currently common practice in many countries) might assist prevent the occurrence of 'connected awareness'.

"It is very important to note that patients did not remember responding to the commands," Sanders says, adding that general anesthetics are generally highly safe.

"It was also reassuring to see that if anesthetic drugs are administered continuously in the time period between induction of anesthesia and intubation, the risk of connected consciousness was greatly reduced," he adds.