Geriatric Anesthesia Research Unit (GARU)

Summary Science Features

As clinicians and researchers continue to learn more about the basic mechanisms of general anesthesia, they are better able to formulate safe and effective regimens with which to manage patients throughout the perioperative period.  Because geriatric patients often have a variety of medical and physiological problems not present in younger patients, a number of unique clinical challenges can arise.  Due to sophisticated research inquiries in areas such as neuroscience and pharmacology, anesthesiologists have come to appreciate how older patients are generally affected by the surgical experience.  Indeed, the need for such research continues to grow as the population ages.

The short-term and long-term effects of general anesthesia on aging brain function represent a burgeoning area of research interest.  General anesthesia, for instance, has been identified as an important risk factor for post-operative delirium, a circumstance observed in 15-53% of surgical patients; the elderly seem especially susceptible. General anesthesia may also contribute to more subtle forms of postoperative cognitive dysfunction (POCD) that have been observed one week postoperatively in 27% of a series of 1,218 patients and three months postoperatively in 10% of the same patient group. Following coronary artery bypass graft surgery, investigators noted POCD in 53%, 36%, 24% and 42% of 261 patients at discharge, at six weeks, six months, and five years, respectively. Because age is one of several risk factors for POCD, these findings suggest that the elderly may have a greater risk for persistent cognitive deficits following anesthesia and surgery. Three separate studies have shown a mild relationship (an odds ratio of 1.2 to 1.6) between previous anesthesia/surgery and the onset of Alzheimer's disease (AD). Further, the age of onset for AD was inversely proportional to the cumulative exposure to anesthesia before age 50. A recent bservational study reported that patients having coronary artery bypass graft surgery under general anesthesia were at increased risk for the emergence of AD as compared to those having percutaneous transluminal coronary angioplasty under local anesthesia. These findings implicate general anesthesia and surgery in postoperative cognitive problems ranging from common delirium to POCD and even AD. Further research into the mechanism and effects of general anesthesia is, therefore, of great importance if we are fully to  understand its possible relationship to these serious sequelae.