November 1, 2013
Automated System Could Monitor Drug-Induced Comas Accurately
Brett Smith for redOrbit.com - Your Universe Online
A patient with a traumatic brain injury will sometimes be placed into a medically-induced coma, which allows the brain time to heal and dangerous swelling to subside. Brought about through the use of general anesthesia drugs, medically-induced comas can last for days.
In the current system, doctors and nurses need to monitor these patients to ensure they are at the right level of sedation. A new study published in the journal PLOS Computational Biology has described an automated system that can follow patients' brain activity and respond accordingly with drug dosages that maintain the correct state.
"Someone has to be constantly coming back and checking on the patient, so that you can hold the brain in a fixed state. Why not build a controller to do that?" said Dr. Emery Brown, a professor of medical engineering at MIT.
Brown and his team started by analyzing brain waves in different states of activity: awake, asleep, sedated and anesthetized. For each state, they were able to select a distinctive electroencephalogram (EEG) pattern.
When patients are in a drug-induced coma, the brain is silent for up to several seconds at a time, which is interrupted by short bursts of activity. This pattern of activity, also called as burst suppression, allows the brain to save necessary energy during times of trauma.
As a patient slips into a drug-induced coma, the person administering anesthesia drugs targets a specific number of "bursts per screen" as brain activity streams across the EEG monitor. This pattern has to be established for hours or days at a time.
"If ever there were a time to try to build an autopilot, this is the perfect time," Brown said. "Imagine that you're going to fly for two days and I'm going to give you a very specific course to maintain over long periods of time, but I still want you to keep your hand on the stick to fly the plane. It just wouldn't make sense."
To automate the monitoring process, the team constructed a communication pathway between the brain and a device made to assist various brain functions. The device included an EEG system, a drug-infusion pump, a computer and a control algorithm. The anesthesia drug propofol was chosen to keep the brain at an ideal level of burst suppression.
In tests on laboratory rats, the computer’s algorithm interpreted the animal's EEG, calculated how much drug was in the brain and adjusted how much of the drug to inject into the rodent on a second-by-second basis.
The system can also regulate the depth of a coma nearly instantaneously, which would be impossible to accomplish manually, the research team said. The system could also be set to take a patient out of an induced coma occasionally so doctors could conduct neurological tests.
"Much of what we do in medicine is making educated guesses as to what's best for the patient at any given time," said Dr. Sydney Cash, an associate professor of neurology at Harvard Medical School who was not part of Brown’s team. "This approach introduces a methodology where doctors and nurses don't need to guess, but can rely on a computer to figure out — in much more detail and in a time-efficient fashion — how much drug to give."