"This human biomarker study gives some credibility to the notion that anesthesia and surgery produce an inflammatory insult on the brain and accelerate diseases like Alzheimer's."
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From time to time, I receive emails from concerned Alzheimer's caregivers that are worried about the potential for memory loss in the their loved one who needs an operation and will be receiving anesthesia.
The following study, though small, will do nothing but increase the anxiety around the issue of Alzheimer's and anesthesia.
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Study Links Surgery and Anesthesia With Alzheimer’s
New research adds to the growing evidence that anesthesia and surgery may be associated with the progression of chronic brain diseases, particularly Alzheimer's disease.
"We have long sought a clearer picture of the true impact of anesthesia and surgery on the central nervous system," study author Dr. Roderic Eckenhoff, the Austin Lamont Professor of Anesthesia at the Perelman School of Medicine at the University of Pennsylvania, said in a university news release.
"Although not definitive, this human biomarker study gives some credibility to the notion that anesthesia and surgery produce an inflammatory insult on the brain and accelerate chronic neurodegenerative diseases like Alzheimer's," Eckenhoff added.
In conducting the study, which is published in the October issue of the journal Anesthesiology, researchers collected cerebral spinal fluid from 11 patients both before and in four intervals after routine endoscopic nasal surgery.
The researchers explained that there are "biomarkers" (or indicators) for Alzheimer's disease found in cerebral spinal fluid. Measuring these indicators, known as amyloid beta and tau protein, can help detect Alzheimer's before symptoms appear and help predict which patients will progress from mild cognitive impairment to full-blown Alzheimer's disease.
High levels of tau protein and decreased amyloid beta are generally considered signs of Alzheimer's, the researchers pointed out in the news release.
Although average amyloid beta concentrations varied by less than 10 percent in either direction and remained unchanged in the 48 hours following surgery, the investigators found significant increases in total tau six hours after surgery. This level continued to rise 48 hours after the operation.
An injury biomarker and three inflammatory biomarkers were also significantly increased over time after surgery, the study showed. Overall, the findings suggest that the changes in the cerebral spinal fluid biomarkers are in line with Alzheimer's disease progression.
The researchers noted that the use of sevoflurane -- one of the most widely used inhaled anesthetics, which may reduce immune responses during surgery -- was associated with significantly higher concentrations of inflammatory biomarkers than other anesthetics.
More research is needed, however, to determine if the management of anesthetics could make a difference in neuroinflammation following surgery, the study authors pointed out.
"The evidence for anesthesia per se being responsible for the changes we saw in this study is not definitive -- in fact, our work in animal models of Alzheimer's is beginning to suggest that the surgical procedure itself produces a larger effect than anesthesia," said Eckenhoff. "The next step in this line of research is to determine whether anesthetic management can modulate the neuroinflammation caused by surgery, whether this brief inflammatory insult can actually change the trajectory of something like Alzheimer's disease, and given that surgery is usually not strictly elective, development of a strategy to reduce the inflammatory insult to the brain."
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