Consciousness can endure despite anesthesia, allowing for a form of “connected consciousness” in which many patients undergoing surgery can communicate with others… even if they are unconscious. A whole revelation about the labyrinths of consciousness.
General anesthesia is intended to provide people with a state in which they can tolerate aggressive surgical interventions.
This state is achieved through a cocktail of drugs that ensure an alteration of consciousness, scientifically known as pharmacological hypnosiswhich leads the person to experience an absence of awareness of their surroundings.
As explained in a 2019 article in the journal Frontiers in Systems Neuroscience, which paints a picture of the current state of knowledge about drug-induced unconsciousness, general anesthesia does not shut down the brain globally and does not always result in a complete absence of consciousness: can be altered to various degrees by the effect of specific medications.
This implies that what anesthesia achieves is to alter consciousness in a reversible way, something that, depending on the drugs applied and the corresponding doses, can have different effects.
Anesthesia and consciousness
A first effect, and it is the one that is really pursued with general anesthesia, is the total absence of subjective experience, also called unconsciousness.
But anesthesia can also cause other states, such as conscious experience without awareness of the environment, called disconnected consciousnesssimilar to what occurs when we sleep.
Finally, general anesthesia can cause a third state, called connected consciousnessduring which the unconscious person maintains a thread of awareness of the environment and can respond to stimuli, such as a handshake.
Another characteristic of the states of consciousness caused by general anesthesia is that each of them can be recalled later in the form of explicit or implicit memories.
For all these reasons, anesthesia is considered a powerful resource for explore consciousness. In recent years, advances in the exploration of brain function have allowed a better understanding of the neural correlates of consciousness and its alterations during anesthesia, without science having yet acquired a clear notion of what consciousness is. in all its dimensions
A new research from the University of Sydney, whose results are published in the British Journal of Anesthesia, sheds new light on the labyrinths through which consciousness runs during general anesthesia processes.
The new research has focused on one of the effects of general anesthesia: connected consciousness. It has found that it affects 1 in 10 young adults, and more women than men.
Connected consciousness refers to the subjective experience of oneself that an anesthetized patient maintains, as well as the perception of information from the environment that they record in an unconscious state, something that can occur in episodes of variable duration.
According to previous research, these episodes of connected consciousness could be observed immediately after laryngoscopy and tracheal intubation in approximately 5% of patients.
The new research breaks this boundary and greatly expands the impact of anesthesia on connected consciousness: it occurs in up to 11% of young adults.
Another important observation: while disconnected awareness refers to internal awareness, connected awareness refers to both external and internal awareness during anesthesia.
External awareness is defined as the perception of environmental sensory stimuli (eg, auditory, visual, olfactory, or somesthetic), whereas internal awareness refers to all thoughts independent of environmental stimuli. Both characteristics are present in episodes of connected consciousness.
In the case of this study, the scientists found that one in 10 of the 338 young adults studied, all between the ages of 18 and 40, responded to prompts asking them to shake the researchers’ hand once if they understood, and twice if they had pain while under general anesthesia.
What’s more, one hour after waking up, the participants were asked to recall 16 words they had heard under anesthesia, to see what they remembered from the experience.
The researchers found that women were two to three times more likely than men to experience “connected consciousness,” the study found.
About 13 percent of the women responded to commands under anesthesia, compared to just 6 percent of the men, despite receiving the same doses of the anesthetic.
The researchers also noted that half of the 37 people who responded to the prompts also reported pain, which led to an increase in the anesthetic dose.
“In our opinion, this is a higher level of consciousness than is anticipated by patients (or their anesthesiologists) during general anesthesia,” the researchers write in their article.
And the last conclusion of this study: only one person clearly remembered the experience of surgery after the procedure was over.
“The study data has provided us with a crucial starting point to further our understanding of connected consciousness,” says lead author, robert sandersit’s a statement.
He adds that this research also highlights the need to better understand how different people respond to anesthetic medication.
“There is an urgent need for more research on biological differences, particularly gender, that may influence sensitivity to anesthetic medication,” he concludes.
Connected consciousness after tracheal intubation in young adults: an international multicentre cohort study. Richard Lennertz et al. British Journal of Anaesthesia, May 23, 2022. DOI: https://doi.org/10.1016/j.bja.2022.04.010