Researchers examined that anesthesia operates in the brain, but the standard protocol among anesthesiologists when monitoring and dosing patients during surgery is to rely on indirect signs of arousal like movement, and changes in heart rate and blood pressure. The key has been to develop a theoretical and analytical understanding of electroencephalogram (EEG) brain wave measurements of patients under general anesthesia.
Researchers will describe how anesthesia's effects in the brain produce specific patterns of brain waves and how monitoring them via EEG data can lead to better care. He's speaking as part of a broader discussion on the use of data analysis in brain research.
In numerous papers over more than a decade, Brown has helped the field understand how different anesthesia drugs, such as propofol, dexmedetomidine and sevoflurane interact with various neuronal receptors, affecting circuits in different regions of the brain.
Those neurophysiological effects ultimately give rise to a state of unconsciousness essentially a "reversible coma" – characterized by powerful, low frequency brain waves that essentially overwhelm the normal rhythms that synchronize such brain functions as sensory perception, higher cognition or motor control. Understanding anesthesia to this degree allows for practical insights.
They showed how stimulating dopamine-producing neurons in the ventral tegmental area of the brain could wake mice up from general anesthesia. The study suggests a way human patients could be awakened as well, which could lessen side effects, recover normal brain function more rapidly and help patients move more quickly out of the operating room and into recovery.
During every surgery, Brown said, he uses real-time EEG readings to keep a patient adequately dosed without giving too much. In a recent case involving an 81-year-old cancer patient, Brown said he could comfortably administer about a third the supposedly needed dose. This can be especially important for older patients.
Older patients are especially susceptible to problematic side effects when they wake up including delirium or post-operative cognitive dysfunction. Neuroscientifically informed ways to prevent giving too much anesthesia can help prevent such problems, Brown said.
The SS-MT method produces high-resolution, low-noise spectrograms from such data. In the study, he used SS-MT to discern variations in EEGs with different states of consciousness in patients who had received propofol.
Ultimately as more anesthesiologists acquire knowledge and EEG equipment, Brown said, and equipment makers produce better displays for their use, the field can move to a model where doctors have a direct view of the patient's brain when monitoring and maintaining their consciousness during surgery.