This is your brain. This is your brain on drugs. Any questions?
Actually, there are. A University professor has been asking many questions about the effect of anesthetics on patients' brain waves recently--and developing ways to monitor these effects.
During surgery, inadequate doses of nerve-numbing anesthetics can leave the patient partially conscious. As many as 30,000 of the 15 million people who are anesthetized during surgery each year aren't fully unconscious, said Dr. Peter Glass, associate professor of anesthesiology.
Some semi-conscious patients recall hearing words spoken during surgery and then falling back asleep, Glass said. Others tell horrific stories: Glass recounted the story of one patient who remembered "`the knife going into my belly, and I was paralyzed and unable to tell you that this was happening to me.'" Such memories can cause long-term symptoms resembling those of Post Traumatic Stress Disorder, such as insomnia and chronic anxiety.
"[Recall] is a relatively rare event, but it can be a real problem when it happens," Glass said. In addition, most cases of surgery recollections go unreported because people think they are dreams, Glass added.
In conjunction with colleagues at Emory, Harvard and the University of Pittsburgh, Glass has developed a new brain-monitoring software with Aspect Medical Systems, which may reduce the likelihood that patients will regain partial consciousness during surgery.
Speaking Tuesday in Atlanta, Ga., Glass and his colleagues presented the findings of their latest study on 70 patient volunteers at the annual meeting of the American Society of Anesthesiologists.
The software, which runs on conventional electroencephalographic machines, measures brain wave patterns, informs doctors how much anesthesia needs to be administered, and alerts doctors when the dosage needs to be increased. While EEG machines display brain wave patterns and provide information about the responsiveness of the patient, Glass said that "for the first time somebody has taken the [monitoring device] and has quantified the sleepiness of the brain [according to] concentrations of dosage."
The experimental software, which is awaiting approval for use in the operating room from the Food and Drug Administration this month, analyzes brain wave patterns to create an index indicating levels of consciousness. The software rates consciousness on a scale of zero, which indicates that a patient is fully unconscious, to 100, which indicates that the patient is fully conscious. As numbers rise on the monitoring device, a doctor would know to increase the level of anesthesia, Glass said.
A rating of 70 or below indicates "a very low probability" of recall, Glass said. Levels between 60 and 70 are a source of concern, and numbers above 70 are associated with being awake and being able to recall events, he said.
Researchers developed the ratings by showing picture cards to the study's patient volunteers while administering varying dosages of anesthesia, monitoring changes in the patients' brain activity, and assessing patients' ability to recall the pictures.
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