Anesthesia and the Brain
“Watch what happens,” Emery Brown, AB ’78, AM ’84, MD ’87, PhD ’88, says as he plays a video of brain wave recordings, using electroencephalography (EEG), from one of his patients starting to receive anesthesia at Massachusetts General Hospital (MGH). “You’re going to see when the drug starts to work. Boom. See those small, regular oscillations? The patient is becoming sedated. And now these big oscillations come on, and the patient becomes unconscious.”
Brown, an anesthesiologist, statistician, and neuroscientist with endowed professorships at Harvard Medical School and MIT, studies how anesthetics work in the brain. His pioneering research holds promise for improving the delivery and safety of general anesthesia and for developing new ways to create, monitor, and control the state of general anesthesia.
According to Brown, anesthetic drugs cause brain circuits to change their oscillation patterns in particular ways, thereby preventing neurons in different brain regions from communicating with each other. The result is a loss of consciousness—an unnatural state that he compares to a “reversible coma”—that differs from sleep. The oscillations vary, he explains, based on the type and amount of anesthetic used and the age of the patient’s brain (since brains age at different rates). These powerful drugs can cause mental side effects that often linger for days, months or longer.
Brown uses EEG to measure these oscillations, drawing on his knowledge of signal processing and statistics to examine these wave patterns. He makes sure that all of his patients are connected to EEG machines to monitor their brains’ electrical activity during surgery under general anesthesia. He recommends that all practicing anesthesiologists use this approach, “because it gives a much clearer understanding of how unconscious patients are, and it allows them to titrate the drugs in a more principled manner.”
Brown and his team, who collaborate with investigators across Boston, are developing new monitoring and dosing strategies to help anesthesiologists administer the most appropriate doses for each individual patient. They are also studying the use of the stimulant Ritalin to help patients waken quickly.
Marrying His Interests
Brown’s curiosity, collaborative spirit, and role as both clinician and investigator drove him to explore the neuroscience behind general anesthesia, undergone by millions of people to withstand painful surgical procedures.
In the late 1990s, Brown was practicing anesthesiology at MGH and studying circadian rhythms in mammals when he shifted his research focus to computational neuroscience. He began working with MIT colleagues to develop statistical methods and signal-processing algorithms for analyzing neural data; for example, how does a rat’s brain represent space when it runs around? About 15 years ago, Brown began wondering whether these systems neuroscience approaches could inform his “day job” and began building an interdisciplinary research team to explore how the brain responds to anesthesia.
Brown stresses the need to recognize anesthesiology as a field of clinical neuroscience and to lift the shroud of mystery that, he contends, envelops the specialty. Anesthesia, he says, “is not a black box. It’s not a mystery.”
We have Emery Brown and others to thank for that.
Debra Bradley Ruder is a freelance medical writer based in Greater Boston.