Recent Studies Offer Fresh Insights Into Postoperative Cognitive Dysfunction

Main Category: Seniors / Aging
Also Included In: Neurology / Neuroscience;  Cardiovascular / Cardiology;  Clinical Trials / Drug Trials
Article Date: 23 Dec 2007 - 0:00 PDT

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A pair of recent studies are helping to pave the way for future treatment of the long misunderstood condition of postoperative cognitive dysfunction (POCD) in the elderly.

A prospective, longitudinal study of 1,064 patients by Terri G. Monk, M.D., Duke University, is the first to look at postoperative cognitive changes following major noncardiac surgery of patients of all ages. The other study, by Catherine C. Price, Ph.D., University of Florida, utilized data collected by Dr. Monk's group and is the first to pinpoint the specific types of cognitive decline that occur after surgery.

Postoperative cognitive problems have been often associated with cardiac surgery in the elderly. Dr. Monk's studies not only provide insight into POCD following noncardiac surgery in the elderly but also in younger patients.

"This study demonstrated that elderly patients are at an increased risk for postoperative cognitive problems when compared to younger patients," Dr. Monk said. Her study is also the first to report an association between the occurrence of POCD and an increased risk of mortality in the first year after surgery.

In Dr. Monk's study, patients categorized as young (18-39), middle-aged (40-59) and elderly (60 or older) were given neuropsychological tests prior to surgery, at hospital discharge and three months after surgery.

Patients who had POCD at hospital discharge and at three months after surgery were more likely to die during the first year after surgery. The one year mortality of patients without POCD was 2 percent. Patients with POCD three months after surgery saw mortality rates increase to 4 percent during the next year. At the three-month testing stage, POCD occurred in nearly 12.7 percent of elderly patients, which was significantly higher than middle-aged patients (5.7 percent) and the young (5.7 percent).

The link between POCD and mortality is unclear. Previous studies indicate that mortality risk is often related to a patient's underlying medical conditions. It is possible that patients with prolonged cognitive problems after surgery might not adhere to medication or therapy regimens or may not respond to symptoms of complications by arranging for medical followup, Dr. Monk said. Patient perception of loss of intellectual or physical function may also contribute to depression, which has been shown to be an independent co-factor when determining mortality risks in the elderly.

In her study, Dr. Monk and colleagues identified four risk factors that contributed to long-term POCD: increasing age, lower educational level, history of a previous stroke with no residual neurologic problems and cognitive impairment at time of discharge.

As future studies add to a better understanding of POCD, Dr. Monk said that the next step in managing cognitive dysfunction is learning how to prevent it in the first place. Research into the causes and methods to prevent postoperative cognitive problems are extremely important because the elderly population is the fastest growing segment of the population. Previous recent studies have shown that "effortful" mental activity may decrease or delay the onset of cognitive decline, but Dr. Monk stressed that more research is needed before specific preventative actions can be recommended.

Expanding upon Dr. Monk's results, Dr. Price and colleagues were the first to identify types of cognitive decline, which were divided into problems with 1) memory and 2) executive function (concentration). After three months, Dr. Price found that more older adults experienced memory decline, but only those who had problems with concentration or combined memory and concentration problems experienced functional limitations at home. This group tended also to be less educated than those with no impairment and with only memory problems.

"Understanding the type of cognitive problem after surgery may help us to develop strategies for preventing postoperative cognitive decline," Dr. Price said. "It is known, for instance, from traumatic brain injury and stroke research that the type of cognitive impairment influences inpatient and rehabilitation strategies. The same may hold true for different types of postoperative cognitive impairment."

Anesthesiologists have been at the forefront of research into POCD, but as they gain greater understanding of this phenomenon, they are also poised to apply this knowledge directly to patient care. In a companion editorial to the two studies, Mervyn Maze, M.B., Ch.B., Imperial College School of Medicine-Chelsea and Westminster Hospital, London, sees anesthesiologist-led research into POCD as crucial for science and for our aging society.

"The attempt to understand POCD can be seen as part of a quest to control the processes of aging and the postponement of cognitive decline," Dr. Maze said. "Those involved in the care of elderly patients scheduled for surgery need to identify the pathogenic mechanisms and orchestrate protective and therapeutic interventions to target the processes that produce POCD. While the anesthesiologist may not have all the necessary tools to undertake this quest, they are strategically placed to lead the response to this perioperative challenge."

Founded in 1905, the American Society of Anesthesiologists is an educational, research and scientific association with 43,000 members organized to raise and maintain the standards of the medical practice of anesthesiology and improve the care of the patient.

Visit the ASA Web site at http://www.asahq.org.

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