Study Delves into Mysteries of Anesthesia and Coma

Amanda Chan

Date: 03 January 2011 Time: 02:41 AM ET

Under general anesthesia, the brain's state is more akin to being in a coma than being asleep, a new study shows.

The findings show that, by studying the areas of the brain that anesthesia turns off, scientists may develop a better understanding of the brain regions affected when someone is in a coma, said study researcher Dr. Emery Brown of Massachusetts General Hospital in Boston.

And by understanding the similarities between coma, anesthesia and sleep, doctors may find ways to coax patients out of comas or make more effective sleep medications, the researchers say.

Their findings were published Dec. 30 in the New England Journal of Medicine.

The anesthetized mind

Most people are comfortable not knowing much about what happens to their brain under anesthesia, as long as they don't feel anything while they’re under and are able to wake back up, Brown said.

"We've been comfortable treating anesthesia as a black box," Brown told MyHealthNewsDaily. "As long as you give the drugs and people lose consciousness, and come back and seem OK, you can [do] that and not truly understand how it works."

Brown and his colleagues — including a coma recovery expert and a sleep expert — analyzed 100 human and animal studies on anesthesia, sleep and coma.

The researchers discovered similarities and differences between the parts of the brain affected by each state.

For example, one study they analyzed showed that when someone takes the anesthesia drug propofol, four main areas of the brain are affected: the cortex, which plays a central role in memory; the thalamus, which regulates consciousness; the top of the mid-brain where the arousal center is located, and the low part of the brain stem, where breathing is controlled, Brown said.

The researchers discovered that these same four sites are affected when a person is in a coma. So propofol actually works by putting the brain into a drug-induced coma, he said.

By understanding this, an anesthesiologist is better able to reassure patients, he said.

"You can feel comfortable saying, 'You'll be unconscious, but I can reverse it because of this reason,'" Brown said.

How drugs affect the brain

The doctors also found commonalities in how drugs affect these brain states.

For example, anesthesiologists try to administer only as much of a drug as is necessary. If an anesthesiologist gives too much, the patient can become excited, and then the dose has to be further upped to accommodate this.

The researchers saw the same effect with the sleep aid Ambien, Brown said. For people in a coma, the brain region called the globus palladis, which regulates voluntary movement, is damaged, and it stops the action of the thalamus, which regulates consciousness.

Ambien helps people enter a state of sleep. But at certain doses, Ambien can deactivate the globus palladis, which in turn activates the thalamus so the person can regain consciousness, Brown said. In other words, Ambien can sedate, but it can also help patients in a coma wake up.

By opening the lines of communication among researchers studying anesthesiology, coma and sleep, doctors will be able to find better solutions to common problems patients face, Brown said.

And for anesthesiologists, the findings could lead to better drugs, so patients can recover with a clear head, without being sick to their stomachs and without waking up during the surgery, Brown said.

Brown and his colleagues are applying the findings of the study to new research studying anesthesia and coma in both animals and humans.

Pass it on: Being put under anesthesia is more similar to being in a coma than to being asleep.

Follow MyHealthNewsDaily staff writer Amanda Chan on Twitter @AmandaLChan.