Waking Up During Surgery

An awakening in the midst of surgery is a patient’s and an anesthesiologist’s nightmare.

British scientists have developed a new way to prevent that.

By measuring brain waves, they reported, it’s possible to titrate the appropriate amount of the drug needed to put a patient under.

This discovery is important because of the “considerable variability” in individuals’ responsiveness to anesthesia, the University of Cambridge team said in a study published in the January 14 issue of PLOS Computational Biology.

“By measuring their behavioral responsiveness and the amount of sedative in their blood, we found a striking pattern: the strength of their brain networks before sedation predicted why some participants lost consciousness while others did not, despite registering similar blood levels of the drug,” senior author, Tristan Bekinschtein, PhD, of the University’s Department of Psychology, and his colleagues reported.

“By uncovering underlying signatures of this variability, our findings could enable accurate brain monitoring during anesthesia and minimize intra-operative awareness.”

The team used high-density electroencephalography (EEG) to study how 20 healthy adults’ brain networks changed as they were sedated by propofol.

EEG tracking during sedation hasn't been common because of the lack of robust EEG markers that show the loss and regaining of consciousness, according to the study. That practice could change with the group’s discovery of such markers.

“EEG machines are commonplace in hospitals and relatively inexpensive,” Bekinschtein said. “With some engineering and further testing, we expect they could be adapted to help doctors optimize the amount of drug and individual needs to receive to become unconscious with increasing their risk of complications.”

Using nine male and 11 female test subjects, the researchers looked at the correlation between blood levels of propofol and alpha and delta brain waves.

The subjects received increasing doses of the anesthetic as they were asked to press different buttons when they heard a ping or a pong, while an EEG tracked their brain waves. At the maximum dose 13 maintained consciousness and continued pushing buttons while others were unconscious. Both before and after the anesthesia, the alpha networks were most predictive of which group lost consciousness.

These results “if replicated and verified in the clinical context, could contribute reliable applications of brain monitoring for tracking and accurately modulating consciousness with anesthetics during routine surgery,” the study concluded.