Many older adults experience delirium, defined as a state of confusion or agitation, following major surgery. Previous research has suggested that closely monitoring the patient’s brain activity and making adjustments to protect the brain from too much anesthesia can lower the risk of postoperative delirium.
But in a new study of more than 1,200 older surgery patients, researchers at Washington University School of Medicine found that even when they meticulously watched brain activity and took great care to minimize levels of anesthesia during surgery, it still had no significant effect on the occurrence of delirium.
“The thought has been that at certain levels of anesthesia, brain activity is suppressed, and that is what mediates these problems,” said first author Troy S. Wildes, M.D., an associate professor of anesthesiology. “But we found that preventing suppression by closely monitoring and then adjusting doses of anesthesia made delirium no less likely.”
Still, the study revealed an unexpected finding: There were fewer deaths in the first 30 days post-surgery among patients who did receive close brain monitoring. The researchers believe this points to the potential benefits associated with close brain monitoring and should be investigated further.
The researchers defined major surgery as procedures requiring at least two hours of general anesthesia and at least two days in the hospital following the operation. This includes procedures such as cardiac, gastrointestinal, thoracic, gynecologic, urologic and vascular surgeries.
For the study, half of the 1,232 patients were randomly assigned to very close monitoring of the brain’s electrical activity, as measured by electroencephalogram (EEG) during surgery, and the rest of the participants were given usual care during their operations.
Overall, the findings show that 26 percent of the closely monitored patients still developed delirium in the first five days after surgery, compared to 23 percent of those who did not receive such close monitoring. This difference is not considered statistically significant.
Surprisingly, however, there were fewer deaths among patients whose brain activity was monitored closely and anesthesia levels adjusted. In that monitored group, four of 614 patients — fewer than 1 percent — died in the month after surgery. Among the 618 patients who did not receive such close brain monitoring, 19 — just more than 3 percent — died within 30 days of their surgeries. That difference is statistically significant.
“I believe we should monitor the brain of every single patient during general anesthesia, just as we routinely monitor heart and lung function,” said principal investigator Michael S. Avidan, M.B.B.Ch., the Dr. Seymour and Rose T. Brown Professor of Anesthesiology.
“Monitoring other organs during surgery has become the standard of care, but for some reason, even though the brain is the target of anesthesia drugs, this type of close monitoring and adjustment has never become routine.”
Although delirium is a major problem that affects around 25 percent of older surgery patients, doctors and nurses may not recognize it.
“There are two common types of delirium: hyperactive, in which the patient is agitated, thrashing, maybe trying to pull out intravenous lines; and hypoactive, in which patients get very lethargic,” said co-first author Dr. Angela M. Mickle, a clinical research coordinator in the Department of Anesthesiology. “Because it’s so common for surgery patients to be lethargic after an operation, delirium often goes underdiagnosed.”
The findings are published in the Journal of the American Medical Association (JAMA).