The 25th annual Swartz Foundation Mind/Brain Lecture featured anesthesiologist-statistician Emery N. Brown, MD, who treated attendees to an accessible primer of anesthesia, offering thoughts on how to leverage current knowledge to deliver safer and more effective treatment to patients.
The lecture, “Deciphering the Dynamics of the Unconscious Brain Under General Anesthesia,” was delivered April 10 at the Staller Center for the Arts. Brown is the Edward Hood Taplin Professor of Medical Engineering and Computational Neuroscience at Massachusetts Institute of Technology and Warren M. Zapol Professor of Anaesthesia at Harvard Medical School/Massachusetts General Hospital.
The Swartz Foundation was established in 1994 to explore the application of physics, mathematics, and computer engineering principles to neuroscience, as a path to better understanding the brain/mind relationship.
The discovery of anesthesia nearly 180 years ago transformed surgery overnight from trauma and butchery to a humane and often life-saving procedure. But Brown said evolution has been slow and the field has not progressed along with new knowledge that has been learned.
“We actually do what’s called ‘balanced anesthesia,’” said Brown. “We use combinations of drugs to create the anesthetic state. You’re first induced by getting a drug like propofol to make you unconscious and we keep you unconscious by maintaining it as an infusion.”
Brown suggests that anesthesiologists can track neural oscillations — or brainwaves — in the operating room to monitor the state of a patient under anesthesia. These oscillations are a fundamental mechanism that enables the synchronization of neural activity within and across brain regions, and promotes the precise temporal coordination of neural processes underlying cognition, memory, perception, and behavior.
“These oscillations provide insight into the unconscious,” said Brown. “The reason I make this point is that using EEG, which measures electrical activity in the brain using electrodes attached to the scalp as I’m suggesting here, is not the standard of care in the hospitals in the United States. In fact, in our own institution, only about 20 percent of our anesthesiologists use it, and that’s about the same number across the country. That’s just a habit of the way the practice takes place, and that is something we’re trying to change.”
Brown noted that EEGs and spectrometers, which measure variations in physical characteristics, are key to helping administer more accurate dosages, and facilitating better outcomes.
“Anesthesiologists don’t use EEGs and then don’t think of the brain under anesthesia as a neuroscience question,” he said. “Beginning about 10-15 years ago, we were using the EEG very systematically to understand the oscillation patterns. The capacity to monitor has been there for years, it just has not become part of practice. We get a lot of pushback because the field is basically resistant to this change. But I’ve been able to design whole new anesthesia paradigms to more carefully titrate the drugs using the EEG, and that would change practice quite a bit.”
Brown said that it hinders the public’s understanding of anesthesia when medical professionals equate it with sleep.
“Very often anesthesiologists say to a patient, ‘Mr. Jones, I’m going to put you to sleep,’” said Brown. “We can’t say ‘Mr. Jones, I’m going to put you in a drug-induced reversible coma. But don’t worry, I can wake you up.’ The patient would hop off the operating table.”
Instead, Brown is a proponent of communicating a more clinically accurate definition.
“I tell my patients ‘you’re going to be unconscious and unaware of what’s going on. You won’t have any memories of what’s going on,” he said. “I’ll be monitoring you so the surgeons can operate. I’ll watch your heart rate, blood pressure and temperature and IQ, and I’ll take care of you.”
Brown also noted that it’s important to differentiate between sleep and anesthesia.
“The brain is doing different things,” he said. “In sleep you go back and forth between non-REM and REM sleep about four to six times a night. Roughly every 90 minutes or so we wake up from REM sleep. That’s when our brain is most active. We’re probably dreaming. But that’s a totally different state then the brain oscillating under anesthesia.”
A greater insight into the brain of each individual patient would also help anesthesiologists administer better, safer dosing.
“If you need surgery, there are very few things that we can do right now to make your brain automatically healthy so you could tolerate anesthesia better,” Brown said. ‘The onus is on the anesthesiologist to make his or her care better and for the moment the main thing they can do is monitor and adjust the dose of the drug so you only give the person exactly what they need.”
While drugs are used to induce unconsciousness, they are not used to bring patients back actively, Brown said, which affects recovery time.
“We give you drugs to anesthetize you but we don’t give you drugs to turn your brain back on, and there is work that shows that this is very possible,” he said. “We just let the drugs wear off. Imagine your brain under anesthesia for hours of surgery. To think that it’s just going to immediately pop back and be normal makes no sense. Anyone can knock you out. My job is to bring you back.”
– Robert Emproto