A routine administration of high concentrations of oxygen for several hours during or after surgery may hasten memory loss among people predisposed to Alzheimer's disease or with excessive amounts of beta amyloid in their brains, according to an animal study.
Researchers at the University of South Florida and Vanderbilt University used mice genetically altered to develop abnormal levels of the protein beta amyloid, which deposits in the brain as plaques, and eventually leads to Alzheimer's-like memory loss as the mice age.
They found that young adult Alzheimer's mice exposed to 100 per cent oxygen during several 3-hour sessions showed substantial memory loss not otherwise present at their age.
Young adult Alzheimer's mice exposed to normal air had no measurable memory loss, nor did normal mice without any genetic predisposition for Alzheimer's disease.
"Although oxygen treatment beneficially increases the oxygen content of blood during or after major surgery, it also has several negative effects that we believe may trigger Alzheimer's symptoms in those destined to develop the disease," said USF neuroscientist Dr. Gary Arendash.
"Our study suggests that the combination of brain beta amyloid and exposure to high concentrations of oxygen provides a perfect storm for speeding up the onset of memory loss associated with Alzheimer's Disease," added the study's lead author.
Dr. L. Jackson Roberts II, at Vanderbilt University School of Medicine, of added: "Postoperative memory loss can be a fairly common and devastatingly irreversible problem in the elderly after major surgical procedures.
There has been much speculation as to the cause of this memory loss, but the bottom line is that no one really knows why it happens. If all it takes to prevent this is reducing the exposure of patients to unnecessarily high concentrations of oxygen in the operating room, this would be a major contribution to geriatric medicine."
The authors caution that the study in mice may or may not accurately reflect the effects of receiving high concentrations of oxygen in human surgery patients.
"Nonetheless, our results call into question the wide use of unnecessarily high concentrations of oxygen during and/or following major surgery in the elderly.
These oxygen concentrations often far exceed that required to maintain normal hemoglobin saturation in elderly patients undergoing surgery," Roberts said.