Anesthesia Remains Mysterious

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It's a staple of modern medicine, but how anesthesia works in the brain is still a mystery—even to doctors who use it.

Anesthesiologists are skilled at administering the chemical agents and keeping patients’ vital functions normal while they’re under. Still, no one is sure what happens in the brain that makes people impervious to pain and completely immobile.

“Pathways in your body take information about pain from what we call the periphery up to the brain to process it," said Dr. Emery Brown, an anesthesiologist and professor in MIT’s Department of Brain and Cognitive Sciences. "So I could stop you from feeling pain by blocking it from going in, from being transmitted, from being processed—there are a number of different ways to get to the same end effect."

With this year marking the 160th anniversary of anesthesia’s debut in the operating room, Brown is hoping to finally unravel the mystery of how it works by imaging brains of patients as they go under.  Up to now, most research was aimed at assuring safety and minimizing side effects.

Brown and his colleagues have tested twelve subjects so far, all of whom had tracheostomies, so their breathing is already through a tube, making it easier for researchers to regulate. As the subjects receive an anesthetic drug, they are asked to respond to simple commands by pushing a button. When they stop responding, researchers take pictures of the brain using MRI and fMRI machines and look at brainwaves using an EEG.

The group will need to test more subjects before drawing conclusions, but Brown is already thinking about implications the results could have.

“A large reason that we have problems is because of side effects from the agent acting somewhere other than where we want it to," Brown said. "It makes the brain go to sleep, but it also depresses the heart, dilates blood vessels, and makes it more difficult to breathe.” Ideally, he said, scientists would be able to develop target-specific drugs that work only in localized areas of the brain and leave everything else alone.