Author: Bob Kronemyer
Older adults undergoing surgery with anesthesia may experience mild cognitive impairment afterward, according to a prospective study published in the British Journal of Anaesthesia.
The study of 1,819 people, with a median follow-up of 5.1 years after exposure to anesthesia, and four cognitive assessments found a subtle decline in cognitive z scores that were 0.2 standard deviations more than expected from aging alone (Br J Anaesth 2018;121:398-405).
“I was surprised by this finding because our previous studies of older adults undergoing surgery with general anesthesia showed a lack of association between anesthetic exposure and permanent cognitive impairment,” said principal investigator Juraj Sprung, MD, PhD, a professor of anesthesiology and consultant in the Department of Anesthesiology and Perioperative Medicine at Mayo Clinic College of Medicine and Science, in Rochester, Minn.
“On the other spectrum of life, we occasionally hear anecdotal reports from relatives of older patients who state that their family member was never the same person after undergoing anesthesia,” Dr. Sprung said.
“However, most of these early observational studies found no association between exposure to anesthesia and brain function,” Dr. Sprung said.
The current study, which began in 2004, enrolled people between the ages of 70 and 89 years. Overall, 67% of participants (n=1,218) had been exposed to at least one general anesthetic and surgery or procedure in the 20-year period before their index cognitive assessment, whereas 50% of study patients had at least one exposure in the past 10 years and 33% in the past five years. Patients with previous exposure mainly were male and had a higher comorbidity index.
Small Effect, Not Necessarily Attributable to Anesthesia
The study found that cognitive decline occurred in the memory and executive function domains. “These two domains are the same that first decline with normative aging and Alzheimer’s disease pathology,” Dr. Sprung said.
Quantitatively, the extent of the effect that can be attributed to anesthesia and surgery was small. For a person with no prior exposure but with exposure after enrollment, the decline in cognitive function over a five-year period after exposure was 0.2 standard deviations below the normative means for the expected decline as a result of aging.
“The study did not pinpoint anesthesia as the primary culprit,” Dr. Sprung said. “We accounted for numerous risk factors, including comorbidities known to be associated with cognitive decline. However, there is always the possibility for the presence of unknown confounding factors that remained unaccounted.”
Dr. Sprung stressed it is not possible to determine whether anesthesia, surgery itself, or the underlying conditions necessitating surgery caused the decline.
Based on the study results, he recommended that clinicians not change their practice habits. “I do not think we have any alternatives, because if a patient needs surgery, he also needs anesthesia.”
Nonetheless, patients and their families should be informed about a potential risk for cognitive decline. As for proceeding with surgery, “that is a matter of medical indication, and ultimately the patient and provider must agree on how to proceed,” Dr. Sprung said. “In instances where surgery is not absolutely needed or alternative treatments are available, other options should be considered, especially in older individuals with preexisting cognitive impairment.”
It has been shown that if a person is close to the threshold at which cognitive impairment becomes manifest, exposure to anesthesia and surgery can tip that patient over the limit. “In some individuals, this decline may be permanent. Therefore, both patient and family should be informed of this possibility,” Dr. Sprung said.
According to Dr. Sprung, presurgery testing for cognitive ability would be helpful in determining the patient’s preoperative cognitive level and could help to pinpoint those patients who are more likely to have impairment after anesthesia. He noted that the American Geriatrics Society endorses routine preoperative evaluations of elderly individuals, but that initiative has not been routinely implemented.
Dr. Sprung emphasized that the change in ability after exposure to anesthesia and surgery at older ages is very minimal. “For a fully cognitively normal person, this change induced by anesthesia and surgery would probably not be visible during the remainder of his or her lifetime,” he said.