Doctors develop protocol to detect patient consciousness during surgery
Waking up during surgery and yet still being too anesthetized to signal doctors that you’re awake sounds like a nightmare, and for some people is a genuine phobia. According to New Scientist, a team at the Massachusetts Institute of Technology (MIT) has identified a “consciousness signature” in brain activity that can recognize when a person is waking up.
In approximately .02 percent of surgeries performed worldwide, patients find themselves conscious and aware of what’s happening to them. The Associated Press reported in 2008 that approximately 30,000 Americans a year awaken during surgical procedures, sometimes experiencing intense pain and terror. The phenomenon is more common in children than adults. Keeping track of patients’ brain activity during surgery could be the solution.
“It’s slightly frightening that millions are given anaesthesia every year and the anaesthetist has no way of knowing with certainty that the patient is unconscious,” said Tony Absalom of the Netherlands’ University of Groningen.
The MIT team, headed by Emery Brown, tested 10 adult volunteers, strapping an electrode cap with 64 electrodes to their heads and using the cap to measure changes in brain activity across multiple regions of the brain us they were put to sleep using a general anesthetic.
As the volunteers lost and regained consciousness, they were asked to press a button whenever they heard a clicking sound or if they heard people talking. This allowed scientists to analyze patterns of brain activity during different stages of wakefulness. The team identified patterns related to consciousness and unconsciousness, and were thereby able to determine when a patient was waking up.
Carol Weihrer of Reston, Virginia described the sensation to the AP of waking up during surgery to remove a diseased eye. She heard the doctor give the instructions to “cut deeper, pull harder.”
“I actually saw them cut the optic nerve when everything went black,” she said. “While you’re laying there on the table, you are thinking, praying, cursing, plotting, pleading, trying to crawl off the gurney, trying to kick, scream, move any part of your body to let them know you’re awake. In effect, you are entombed in a corpse.”
Kathy LaBrie of Nashua, New Hampshire woke up during surgery to correct a deviated septum. She heard “the sound of pushing and grinding and the surgeon talking to the nurses about the kind of car he had. I tried moving my arms and legs — I couldn’t do anything. I thought I was dying.”
Ram Adapa at the University of Cambridge told New Scientist, “The mechanisms underlying anaesthesia remain a mystery.”
Brown’s study suggests that anesthesia affects communication and synchronization of the different regions of the brain. Adapa called the results, “another piece of the jigsaw puzzle.”
In the U.K., 2 percent of hospitals do EEG monitoring during surgery, but even these hospitals use a 3-electrode, forehead-only version of the electrode cap. It only monitors one region of the brain and can only determine a probability of unconsciousness.
University of Groningen’s Absalom said, “You don’t want something that says a patient is probably asleep. You want to know ‘Are they or aren’t they?'”
The MIT team’s 64-electrode cap could bring doctors new insight into patients’ levels of awareness during surgery, but it requires patients to shave their heads, which many might prove unwilling to do. In addition, certain kinds of mechanical and electrical interference play havoc with EEG readings, exactly the kinds of mechanical and electrical interference typically found in operating rooms.
[image via Shutterstock.com]