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Similarities Between Anesthesia, Coma Discovered

December 30, 2010

The biological effects of general anesthesia are more closely related to those of a coma than natural sleep, claims a new study published in Thursday’s edition of the New England Journal of Medicine.

While often times doctors and patients describe being under anesthesia as something similar to going to sleep, the researchers behind the new study have found “significant differences” between the two states, Julie Steenhuysen of Reuters reported on Wednesday. For example, while sleep usually involves different types of phases, a patient under general anesthesia typically only experiences one, which even at its lightest is typically far deeper than the deepest states of sleep.

“A key point of this article is to lay out a conceptual framework for understanding general anesthesia by discussing its relation to sleep and coma, something that has not been done in this way before,” lead author Dr. Emery Brown of the Massachusetts General Hospital (MGH) Department of Anesthesia, Critical Care and Pain Medicine, said in a statement.

“We started by stating the specific physiological states that comprise general anesthesia–unconsciousness, amnesia, lack of pain perception and lack of movement while stable cardiovascular, respiratory and thermoregulatory systems are maintained–another thing that has never been agreed upon in the literature; and then we looked at how it is similar to and different from the states that are most similar–sleep and coma,” Brown added.

While Brown understands why some people have been hesitant to compare anesthesia with a coma, the key difference is that the coma-like state induced in medical procedures is one that “is controlled by the anesthesiologist and from which patients will quickly and safely recover.”

Assisting Brown on the study were co-authors Dr. Ralph Lydic, a sleep specialist from the University of Michigan, and Dr. Nicholas Schiff, an expert in coma from Weill Cornell Medical College in New York.

According to Steenhuysen, Schiff points out that under anesthesia, the brain’s activity levels are drastically reduced, similar to what occurs in a coma, and that there are “hints that some of the circuit mechanisms have some overlap.”

“Moreover, understanding this circuit will help us understand the relationship of brain function to consciousness in general–what it is, how it is produced, and what the variety of brain states truly are,” Dr. Schiff added in a separate statement. “Consciousness is a very dynamic process, and now we have a good way of studying it.”

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