GAINESVILLE, Fla. -- Anesthesia and surgery can impair short-term memory and cause confusion and other cognitive declines in some elderly patients, according to an international study initiated by University of Florida researchers.
One in 10 patients 60 and older suffered some memory loss and a lack of concentration for three months following major surgery with general anesthesia lasting two hours or longer. People between 70 and 80 were twice as likely to have long-term mental impairment as those between 60 and 70.
Doctors say that while most people fully recover, it is possible that some patients may never completely regain their previous level of mental sharpness. Researchers also found a strong correlation between cognitive decline and a person's ability to take care of himself.
The study was conducted with more than 1,000 patients at 13 hospitals in seven European countries and the United States from 1994-96. Researchers detail the results in the March 21 issue of the British medical journal The Lancet.
Dr. Joachim Gravenstein, a graduate research professor emeritus of anesthesiology in the UF College of Medicine, estimates about 200,000 people are affected each year in the United States alone.
"Some may say, 'You're only talking about 10 percent of the elderly patients,' but we're talking about hundreds of thousands of people," he said. "There also is a reasonable worry that the frequency of cognitive dysfunction would be higher in patients with pre-existing psychological problems."
Patients in Denmark, France, Germany, Greece, the Netherlands, Spain, the United Kingdom and the United States were tested before, and one week and three months after, major abdominal or orthopedic surgery. In one of the six tests, patients were shown a single letter from the alphabet and timed while they found it on a page full of letters and crossed it off. The patient then was shown two, and later three, letters to pick out. In another of the tests, participants were shown 15 words three times and asked to recall as many as they could. A control group that did not undergo surgery also was given the same tests, developed by Dutch and British neuropsychologists.
Heart and brain surgery patients were excluded, and participants were screened for other conditions that could skew results.
Angela Lane, a clinical and health psychology graduate student working with assistant professor Duane Dede in the College of Health Professions, administered the tests and collected data for the UF portion of the study. She said she could not tell from talking with the patients after surgery that anything was wrong, but the cognitive decline became obvious with testing.
"What really struck me is the high number of patients -- 26 percent -- who still had significant decline on the second test just before they were released from the hospital," she said. "It makes me wonder how the problems with memory and attention may affect a patient's ability to comprehend the instructions they are given at discharge."
Gravenstein's idea for the study came from his clinical anesthesia experience and his desire to confirm what he has suspected for years.
"There was always a suspicion this was true, because every once in a while I would run into a patient who complained of forgetfulness following anesthesia and surgery with no complications. Several months after what appeared to be normal surgery, some otherwise healthy patients would say, 'You know, ever since I had the surgery I have not been able to play bridge because I can't remember the hands that have been played,' " he said.
But the problem can be much more severe than a game of cards. The study also shows a significant correlation between cognitive decline and a person's ability to perform routine daily living activities such as shopping, house work and bodily care, though the cause-effect relationship has not been established.
"The cognitive decline exists, and it is disturbing," Gravenstein said. "It may, in fact, be pushing some people from independence to dependence because they are no longer able to care for themselves."
Researchers disproved their original theory that low blood pressure and lower levels of oxygen in the blood - occasional postoperative conditions monitored during the study - could be linked to cognitive decline. The study, however, failed to pinpoint an exact cause for the decline.
"The exact cause may be very complex," Gravenstein said. "The anesthetic, other drugs and the specific operation could all play a role. We just won't know until we complete further studies."
Other UF researchers involved in the study, funded by the European Commission and the Anesthesia Patient Safety Foundation, include Dr. Laurie Davies, Dr. Tammie Euliano and Johannes van der Aa of the College of Medicine department of anesthesiology.