Searching for the cause of postoperative cognitive dysfunction
Postoperative Cognitive Dysfunction (POCD) is a decline in cognitive function for weeks or months after surgery. It commonly occurs after cardiac surgery as well as major non-cardiac surgery. (POCD's occurrence after cardiac surgery has been referred to as "pump brain.") It primarily affects older patients. For some time, it has been felt to be caused by an impact on the brain from the use of the cardiopulmonary bypass technique.
To investigate the causes of postoperative cognitive decline, researchers in The Netherlands Medline-based search of all literature published up to June 2011. They reported their findings in the March issue of Anaesthesia.
The researchers found that the focus of research has shifted from cardiopulmonary bypass to other factors such as surgery, anesthesia, and patient-related predisposing factors (i.e., age and atherosclerosis). The researchers found evidence that an immune response might be a key issue for the development of the problem. They reviewed evidence in the medical literature pertaining to the premise that priming of the immune system by aging and atherosclerosis may result in an exaggerated systemic (body-wide) and cerebral (brain) inflammatory response to cardiac surgery and anesthesia; this inflammatory response might cause neuronal loss or dysfunction resulting in cognitive dysfunction.
The researchers note that the American College of Cardiology and the American Heart Association have classified the neurological complications after cardiac surgery into two categories: type I and type II. Type-I includes stroke and transient ischemic episodes, coma and fatal brain injury.
These deficits are clearly defined diagnoses and can be detected by clinical neurological examination. In contrast, type-II neurological deficits are diffuse and not well-defined, and include delirium and postoperative cognitive dysfunction (POCD), involving deficits of memory, concentration and psychomotor speed. They note that at the time of hospital discharge, the reported incidence of POCD is 30–65%. After a few months, the reported incidences are still of the order of 20–40%.
The authors concluded that proving that an immune response is a major factor in the development of postoperative cognitive dysfunction is a difficult and challenging problem. They suggest that development of validated cognitive test batteries, standardized statistical methods, as well as newer and more specific markers of neuronal damage will provide further insight into the problem.
Take Home Message: Any surgical procedure—even a minor outpatient operation—is associated with risk. In many cases, alternatives to surgery are available such as weight loss, other healthy lifestyle changes, and medication. Whenever possible, all alternatives should be explored. If surgery is the best option, it should be performed at state-of-the-art hospital by a board-certified surgeon who has successfully performed a number of procedures. A general rule of thumb is the performance of at least 50 procedures with a good outcome. Information regarding surgeons can be obtained from your state medical board. One good source for hospital’s reputation is the Joint Commission.