Postoperative cognitive dysfunction (POCD) refers to a "mild but possibly long-lasting cognitive fogginess" occurring after surgery and anesthesia. The May issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS), presents a special-focus section on POCD in older adults—including the possible causes and preoperative evaluation of POCD risk.
It's still unknown whether POCD results from some neurotoxic effect of anesthetic agents, or whether it simply reflects a step in the decline of cognitive (intellectual) function in older adults. Articles in the special topic section suggest that patients should be informed of the risk of POCD before surgery, and that anesthesiologists should play a more active role in screening for reduced cognitive function before surgery.
Postoperative Cognitive Dysfunction—What's the Role of Anesthesia and Anesthesiologists?
Although the concept isn't new, POCD has become a focus of increased attention in anesthesiology. Up to half of patients, young and old, have POCD within the first week after surgery. Three months later, 10 to 15 percent of patients still have POCD—"but at this point, the problem is limited to the elderly," according to an introductory editorial by Drs. Gregory Crosby and Deborah J. Culley.
It's unclear what causes POCD—or even whether it exists as a unique disease. One theory is that persistent "fogginess" after surgery may reflect pre-existing cognitive problems in older adults: surgery just "unmasks" intellectual declines that were already present. It has also been suggested that cognitive aftereffects of surgery may result from an inflammatory process.
It's also possible that POCD results from some toxic effect of anesthetic agents on the brain. Such neurotoxic effects have been shown in animal research—and backed up by some studies linking anesthetic exposure in young children to an increased risk of later learning disabilities.
An article by Dr. Roderic G. Eckenoff summarizes the findings from a recent workshop on possible brain effects of anesthetic agents. Most researchers believe that neurotoxic effects can and do occur, especially in brains that are somehow vulnerable. However, the nature of the relationship is unclear; multiple factors are likely involved.
Meanwhile, Dr. Eckenoff suggests that it may be time to start informing patients of the possible risk of POCD before anesthesia. He writes, "A clear and consistent message needs to be understood and articulated by anesthesiologists during the consent process: altered cognitive states after surgery have been reported, and may last for weeks to months or longer." He calls for further research to identify the patients and procedures at highest risk of POCD, and what steps can be taken to reduce that risk.
In an opinion piece, Dr. Brendan Silbert and colleagues discuss the possible role of minimal cognitive impairment (MCI)—relatively mild reduction in intellectual functioning, thought to be an early stage of Alzheimer's disease. Since it's found in nearly seven percent of people over 65, many patients receiving anesthesia likely have MCI. At least some cases of persistent "POCD" in older adults may actually be a step in the process of MCI developing into Alzheimer's disease.
Dr. Silbert and coauthors suggest that anesthesiologists could play an active role in assessing cognitive function in older adults before surgery—just as they currently screen for heart disease risk factors. They write, "The anesthesiologist is ideally placed to contribute to both further research and clinical management of patients with both MCI and Alzheimer's disease."
Drs. Crosby and Culley hope the special focus section will stimulate new discussion and research into the brain's response to surgery, sedation, and general anesthesia. They conclude, "The specter of [POCD] is alarming to patients, families, and anesthesiologists alike, but it is also a strong motivator for learning more and doing better so that our work to heal the body does not harm the brain."
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