This is what happens in our body during a general anesthesia

Scientists from the University of Turku and the Hospital District of Southwest Finland have shown through several surveys that consciousness is not completely lost during general anesthesia, although that the person does not react anymore to his environment.

However, according to these works, experiences and thoughts similar to dreams can still float in consciousness despite anesthesia. Thus, the brain can record speech and try to decipher words, but the person will not understand or remember them.

In this way, it is considered that the state of unconsciousness induced by anesthetics may be similar to natural sleep.
During sleep, people dream and the brain unconsciously observes what is happening and the stimuli in their environment, according to the authors, anesthesia might look more like normal sleep than previously thought .

The study, in collaboration with researchers from the University of Michigan, Ann Arbor, and the University of California, Irvine, USA, is a joint project between the research group assistant professor of pharmacology and anesthesiologist Harry Scheinin, who he studied the mechanisms of anesthesia, and the research group of psychology professor Antti Revonsuo, who analyzed human consciousness and the brain from the perspective of the philosophy and psychology.

This joint research project entitled "The Conscious Mind: Integrating Subjective Phenomenology into Objective Measurements" studies the neural mechanisms of human consciousness and, for this, the changes caused by anesthetics are analyzed by electroencephalogram ( EEG)) and positron emission tomography (PET). Their findings were published in four different publications in the July issues of the two leading journals of anesthesiology.

Effects of anesthesia

In the first part of the study, healthy volunteer participants were anesthetized with dexmedetomidine or propofol. The drugs were administered with computer controlled infusions controlled by the target until the subject lost its reactivity.

From this state, subjects could wake up with slight tremors or a loud voice without changing the infusion of drugs. Immediately after the subjects regained their responsiveness, they were asked if they had felt anything during the period of anesthesia.

Almost all participants reported similar experiences to a dream that sometimes mingled with reality, says Professor Revonsuo.

Subjects received sentences in Finnish during anesthesia, in order to check whether the subjects detected and understood the words or complete sentences while they were anesthetized.

The responses on the EEG showed that the brain can not differentiate between normal sentences and strange sentences, such as "the night sky was filled with clear tomatoes," under anesthesia. Moreover, after waking up, they did not remember the prayers they had heard. The results were the same with both anesthetics, according to the principal investigator, assistant professor Katja Valli.

Subjects also heard unpleasant sounds during anesthesia. After waking, these sounds came back to play and, surprisingly, they reacted faster to them than to the new sounds they had never heard before.

In other words, the brain can process sounds and words even if the subject does not remember it later. Contrary to common belief, anesthesia does not require a total loss of consciousness because it simply disconnects the patient from the environment, says Dr. Scheinin.

The project also investigated the effects of four different anesthetics on regional brain glucose metabolism with PET imaging. The results alleviated concerns about the possible adverse effects of dexmedetomidine on the relationship between cerebral blood flow and metabolism. In the future, the project will further analyze the association between cerebral blood flow or metabolism and the state of consciousness.

Source: 20 minutes

RA