Anesthesia More Similar to Coma than Sleep
When explaining the process for general anesthesia, physicians often correlate the process with deep sleep. However, a review written this week for the New England Journal of Medicine finds that the brain is in a state more similar to a reversible coma than sleep. While this may sound scary, the findings could lead to positive results such as new approaches to general anesthesia, improved diagnosis and treatment for sleep abnormalities, and helping patients emerge from a coma.
General Anesthesia is Essentially a Reversible Coma
Study authors Dr. Nicholas D. Schiff, Dr. Emery Brown, and Dr. Ralph Lydic reviewed previous studies plus work of their own over the course of three years and conclude that activity in the fully anesthetized brain is closer to the deeply unconscious, low-activity state seen in coma patients than that of a person who is asleep. There is only a slight overlap between the deepest states of sleep and the very lightest phases of anesthesia.
Also, while sleeping involves moving through a series of phases, patients under general anesthesia are taken to a specific phase or state and kept there during surgery, more closely resembling coma.
While the brain activity pattern is more similar to a coma, because it is drug-induced, it is reversible. Also, the states differ on time scales. Recovery from general anesthesia takes minutes to hours while recovery from coma takes hours to months – or even years.
The understanding of how these two states are more common than different “is very exciting, because it gives us new ways to understand each of these states,” Says Dr. Schiff, who is a professor of neurology and neuroscience at Weill Cornell Medical College and a neurologist at New York-Presbyterian Hospital/Weill Cornell Medical Center. Dr. Schiff also specializes in recovery from coma.
He hopes the findings can make general anesthesia even safer, especially for the elderly who can experience effects such as slower recovery time and impaired cognitive function afterwards.
Dr. Emery Brown, of Massachusetts General Hospital, the Massachusetts Institute of Technology and Harvard Medical School, hope that the findings will also give new insights into how the brain works in order to develop new sleep aids. The drug zolpidem (Ambien) for example is used to treat insomnia by slowing brain activity in order to allow sleep. But it has also been shown to be useful in restoring communication and behavioral responsiveness in some severely brain injured patients.
"Consciousness is a very dynamic process,” says Dr. Schiff, “and now we have a good way of studying it."
"General Anesthesia, Sleep, and Coma", Emery N. Brown, M.D., Ph.D., Ralph Lydic, Ph.D., and Nicholas D. Schiff, M.D.
N Engl J Med 2010; 363:2638-2650December 30, 2010