Skip to Content
MIT News magazine

Going Under

Exploring the mysteries of anesthesia
April 19, 2011

Since 1846, when a Boston dentist named William Morton gave the first public demonstration of general anesthesia using ether, scientists and doctors have tried to figure out what happens in the brain of an anesthetized patient.

brain quest Emery Brown is studying how the brain responds to anesthesia.

Emery Brown, an MIT neuroscientist and an anesthesiologist at Massachusetts General Hospital, wants to approach the question more rigorously than anyone has done before. Writing in the New England Journal of Medicine, he and two colleagues recently laid out a new neuro­scientific framework for studying general anesthesia by relating it to what is already known about sleep and coma.

Such an approach could help researchers discover new ways to induce anesthesia and improve our understanding of brain problems such as drug addiction, epilepsy, and Parkinson’s disease, says Brown, who is a professor in the Department of Brain and Cognitive Sciences and the Harvard-MIT Division of Health Sciences and Technology. “Anesthesia hasn’t been attacked as seriously as other questions in neuroscience, such as how the visual system works,” he says.

In the United States, 60,000 people undergo general anesthesia every day. Though doctors sometimes tell their patients they will be “going to sleep,” that is not accurate, says Brown. “This may sound nitpicky, but we need to speak precisely about what this state is,” he says.

In the NEJM paper, the researchers define general anesthesia as a “drug-induced, reversible condition that includes specific behavioral and physiological traits”—unconsciousness, amnesia, pain numbing, and inability to move. Body functions such as respiration, circulation, and temperature regulation remain stable.

Using EEG (electroencephalography) readings, which reveal electrical activity in the brain, Brown and his colleagues showed that even the deepest sleep is not as deep as the lightest general anesthesia. The sleeping brain cycles through three stages of non-REM (rapid eye movement) sleep, alternating with REM sleep. Each stage has a distinctive EEG pattern, yet none of those resembles the EEG of a brain under general anesthesia. In fact, general-anesthesia EEG patterns are most similar to those of a comatose brain.

The researchers define coma as a state of “profound unresponsiveness,” and sleep as a state of “decreased arousal.” General anesthesia, Brown says, is essentially a “reversible coma.”

Though general anesthesia is seen as routine, it does hold some risk. Side effects can include blood pressure instability, respiratory depression, and nausea. One in 250,000 healthy recipients suffers complications that prove fatal.

A better understanding of how general anesthesia works at the molecular, cellular, and neural levels could help researchers develop anesthestic drugs that are safer, says Brown.

Keep Reading

Most Popular

A Roomba recorded a woman on the toilet. How did screenshots end up on Facebook?

Robot vacuum companies say your images are safe, but a sprawling global supply chain for data from our devices creates risk.

A startup says it’s begun releasing particles into the atmosphere, in an effort to tweak the climate

Make Sunsets is already attempting to earn revenue for geoengineering, a move likely to provoke widespread criticism.

10 Breakthrough Technologies 2023

Every year, we pick the 10 technologies that matter the most right now. We look for advances that will have a big impact on our lives and break down why they matter.

These exclusive satellite images show that Saudi Arabia’s sci-fi megacity is well underway

Weirdly, any recent work on The Line doesn’t show up on Google Maps. But we got the images anyway.

Stay connected

Illustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.