Researchers is the US have invented a closed-loop system based on brain state monitoring that accurately controls unconsciousness by automating doses of an anaesthetic drug every 20 seconds.
The system could enable anaesthesiologists to deliver less medicine, maintaining exactly the right depth of unconsciousness while reducing postoperative cognitive side effects in vulnerable groups like the elderly.
Corresponding author Emery N. Brown is Edward Hood Taplin Professor of Medical Engineering and Computational Neuroscience at MIT and an anaesthesiologist at MGH.
The researcher said: “One of the ways to improve anaesthesia care is to give just the right amount of drug that’s needed.
“This opens up the opportunity to do that in a really controlled way.”
Brown monitors the brain state of his patients in the operating room using electroencephalograms (EEGs).
The physician frequently adjusts dosing based on that feedback, which can cut the amount of drug he uses by as much as half compared to if he just picks a constant infusion rate and sticks with that.
However, the practice of maintaining dose rather than consciousness level is common because most anaesthesiologists are not trained to track brain states and often don’t take time in the operating room to precisely manage dosing.
The new system is not the first closed-loop anaesthesia delivery (CLAD) system, Brown said, but it advances the young field in critical ways.
Some previous systems merely automate a single, stable infusion rate based on general patient characteristics like height, weight and age but gather no feedback about the actual effect on unconsciousness, Brown said.
Meanwhile, others use a proprietary control system that maintains “black box” markers of unconsciousness to vary within a wide range.
The new CLAD system, developed by Brown and his colleagues at the MIT and MGH Brain Arousal State Control Innovation Center (BASCIC), enables very precise management of unconsciousness by making a customised estimate of how doses will affect the subject and by measuring unconsciousness based on brain state.
The new system uses those measures as feedback to constantly adjust the drug dose.
In the new study, the team demonstrated that the system enabled more than 18 hours of fine-grained consciousness control over the course of nine anaesthesia sessions with two animal subjects.
Though there is more work to do, the authors concluded: “We are highly optimistic that the CLAD framework we have established…can be successfully extended to humans.”