Home > Delirium, Dementia risk, Medical issues, Prevention > What is Postoperative Cognitive Dysfunction?

What is Postoperative Cognitive Dysfunction?

Image courtesy stockimages @ http://www.freedigitalphotos.netIn previous articles, I have talked about the temporary decline in cognitive function — a type of delirium — that can happen to some people as a result of surgical procedures.  Today, I’d like to write about this phenomenon in a little more detail.  In the medical terminology, this is known as Postoperative Cognitive Dysfunction (POCD), and can last for weeks or months after some forms of surgery.  It was formerly assumed that, once a patient has had time for the drugs used in anesthesia to work their way out of the body, the brain should automatically return to its pre-operative state.  However, researchers are discovering more and more that this is not so.

POCD has been the subject of increasing research since 2000, after the publication of a large study conducted in Denmark.  It was reported that age, duration of anesthesia, intraoperative complications, and postoperative infections, were most commonly found to be associated with PCOD, while hypoxia and low blood pressure were not.  It has been found to occur just as often after local-regional anesthesia as after general anesthesia.  Some other factors found to be associated with increased risk for POCD include:

  • Having had major surgery, as opposed to minor procedures.
  • Having had heart surgery, in particular.
  • Being of increased age, when combined with alcohol use/abuse.
  • Having a lower educational level, as opposed to higher.
  • Having a prior history of stroke, even if there was a complete recovery of function afterward. and
  • Having a prior history of Mild Cognitive Impairment or dementia, particularly if there is a prior history of delirium.

There has been a considerable amount of research into the causes of PCOD, and what might be done to prevent it or decrease its severity.  However, one big problem that scientists have encountered is that it is extremely rare for anyone to be given anesthesia without there being some precipitating cause for surgery.  It has been determined that PCOD is most likely due, in large part, to the body’s inflammatory response to surgery — especially in those of increased age.  Because of this, it has been suggested that efforts should be taken to reduce inflammation, both before and after surgery.  This could be done through the use of anti-inflammatory agents before surgery, more closely regulating temperature, or using local-regional anesthesia rather than general.  In the post-surgical phase, close attention should be paid to control of pain and infection.  Another significant cause that has been proposed for PCOD is the body’s stress response to the actual surgery, as well as the anesthesia.

Many of the problems that have been encountered with regards to evaluating the effects of anesthesia on the brain have to do, in large part, with the type of test used and its questionable suitability for the purpose.  For instance, many studies have failed to include a normal control group, or have used tests intended for another purpose.  For instance, the Mini-Mental Status Evaluation is commonly used as a screening tool for dementia.  Mild cognitive dysfunction will not normally be detected using this instrument.  And, since there is only one form of the test, a person who is assessed repeatedly will, quite literally, learn the test and give responses that are not reliable for the purposes intended.  It can be used effectively to exclude patients from studies who have significant levels of pre-existing cognitive difficulties, but other than that it is recommended that other instruments be utilized.

It is estimated that as many as half of patients of all ages have PCOD during the first week after surgery.  Ten to fifteen percent of these patients still have the condition after three months, but the majority of these are part of the elderly population.  One theory is that persistent cognitive dysfunction after surgery is a manifestation of a pre-existing cognitive problem, that simply may not have been outwardly apparent previously.  It has been suggested that it may be appropriate for physicians to warn patients of the dangers of PCOD while in the pre-operative phase.  In addition, some researchers have discussed the possibility of anesthesiologists screening patients’ cognitive function during consultations, just as they do for other risk factors.

Speaking personally, I have noticed (as have others who work in long-term care) that individuals with mild cognitive impairment or actual dementia will almost invariably emerge from certain kinds of surgery with increased functional impairment of cognitive functions.  In particular, it seems that this kind of a response is noted after a hip fracture.  I have wondered, however, if this is due as much to other factors such as the actual trauma of a fall, the pain from the injury, the act of being rushed about from place to place with multiple strangers all working on the patient, the narcotics used to relieve pain, and the restricted mobility (at least initially).  Often a brain that is already impaired in function just has too much trouble assimilating all of the above, and a more permanent decrease in function is the eventual result.

I have also observed, unfortunately, that many health care workers see someone who is having significant cognitive difficulties after surgery, and mistakenly assume that the patient is simply manifesting a new or pre-existing dementia.  As such, there is sometimes little attention paid to helping the patient return to their prior level of function, either through the use of medical means or the careful administration of therapy and compensatory strategies.  Just because an 80-year-old woman is confused and having behavioral problems after surgery to repair a hip fracture doesn’t mean that she must spend the rest of her life in such a condition.  One of my goals, as a therapist, is to educate staff members as well as patients and their families, as to the nature of disorders such as this one, and to attempt to help these individuals return to a better level of functioning — and a better quality of life.



British Journal of Anesthesia

International Anesthesia Research Society

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