Does General Anaesthesia cause memory loss?

Worrying about your upcoming operation is more common than what you believe. There’s a lot to worry about when you undergo surgery- the success of the surgery and of course the anaesthesia to make the surgery possible.


Every day about 11,000 people nationwide in Australia will have surgery which involves an anaesthetic. Many of these people too will be anxious prior to surgery. It’s quite natural to have worries about getting onto the operating table, especially with so many stories and news articles that brings to your attention the dangers of surgery and Anaesthesia.


So why do we need anaesthesia anyway? Well Anaesthesia, being the modern day medical miracle, has allowed surgery to take place when prior to anaesthesia it would not have been remotely possible.


However does rendering someone unconscious have long lasting implications on your memory or brain function after the operation? Does anaesthesia cause memory loss?  To answer this question will require us to take a look at the current research. Knowing this you will have a better idea in how it might affect you, and how you might be able to avoid the complications.


Anaesthesia and long term memory effects

It isn’t uncommon for people to observe elderly surgical patients experiencing confusion after their operation. These symptoms usually fade with time.


However, in recent years, more research has been pointing to something a little more serious—something called postoperative cognitive dysfunction (POCD) . POCD involves problems with memory, attention, and concentration that can last months or sometimes even a lifetime.


Why is this concerning? Well, a 2008 study showed that people who still had POCD 3 months after surgery were more likely to die in the first year after 

surgery (10.6%) compared with patients with no POCD

(2.1%). 



Is there any evidence of Anaesthesia causing memory loss?


Let’s look a little more into the phenomenon known as post operative cognitive dysfunction (POCD), as it’s a condition that has been researched closely.


Most of these POCD studies have focused on the elderly, because that’s where this phenomenon is most commonly seen.

A 2001 paper in The New England Journal of Medicine kept track of patients who received coronary artery bypass surgery using a specific method where a heart-lung machine circulates and oxygenates the blood. The researchers found that many patients complained that they had a mental haziness after the surgery. According to the paper authors, more than half of the patients left the hospital with signs of cognitive decline and 42% were still impaired 5 years later.


Though critics were unsure whether the data (they didn’t have a comparison group of patients with heart disease who didn't undergo surgery) was accurate, later studies revealed that the patients still developed cognitive difficulties at about the same rate whether they had pump or "off pump" surgery.


Other studies have reached different conclusions. For example, in February 2016, an anesthesiologist named Juraj Sprung of the Mayo Clinic and a team looked at the prevalence of mild cognitive impairment (MCI). MCI is essentially a mental downturn that often is a precursor to Alzheimer's disease. The team compared how often MCI appeared in people who had undergone an operation or procedure that required general anaesthetic since the age of 40 against how often it appeared in people who had not. They did not find a link.


But, in 2015, anesthesiologist Katie Schenning of the Oregon Health & Science University in Portland and colleagues found the opposite to be true after analysing data on a similar group of more than 500 elderly patients who were mostly from Oregon. "People who had surgery and anaesthetic declined more rapidly," she says.

Are middle aged people affected by memory loss after Anaesthesia?

  Elderly are not the only patients that are susceptible to memory impairment after surgery .


   In 2018, a new study published in the Medical Journal of Anesthesia began to dig into the evidence around the effect of general anaesthesia on middle-aged patients. In the study, researchers took 964 patients, averaged age 54, from the Wisconsin Registry for Alzheimer’s Prevention (WRAP). The researchers had the participants take two cognitive assessment tests over the course of four years. The scientists were trying to see if one group was more likely to experience a cognitive decline or impaired memory.


What they found was eye opening. Whether one of the 670 participants with normal memory at the start of the study showed signs of “abnormal memory” depended on whether or not they had had surgery.


The participants who had surgery during the study period were nearly twice as likely to have “abnormal memory” than those who didn’t. Amongst other things that the surgery seemed to have affect were issues with executive function, although the memory changes were fairly small. They also found that having surgery was associated with a decline of immediate memory and verbal learning that was double the rate of decline among participants who did not have surgery. 



Apart from Anaesthesia what else may be contributing to memory loss?


All of these results do need to be taken with a grain of salt. Firstly, correlation does not mean causation. There’s evidence that gives us reason to believe that  it maybe not the anaesthesia itself but something else in the surgery contributing to the memory impairment.


Researchers are investigating other potential contributing factors to POCD, such as reduced blood flow to the brain during surgery. Many scientists are now subscribing to the idea that physical trauma of surgery itself might be the cause for this kind of mental dysfunction.


Some researchers’ believe that surgery itself may promote a body-wide inflammation, which then makes its way into the brain. When inflammation is at a high, your body sends chemicals and cells in attack mode all over, including the brain. 


Surgeries in addition may limit blood flow in general, and therefore blood flow to the brain, which may cause cognitive impairment. 


It’s also critical to remember that the designs of these sorts of studies that are looking at surgery and memory impairment are weaker studies than randomised control studies. Again, it may just be a correlation and not causation.


Most importantly, determining the source and frequency of POCD is difficult because the field doesn’t yet have standard diagnostic criteria for it. Depending on the definition, the rates of occurance can range fr

om from 5% to 50%.

Potential ways to Avoid Memory loss
after Anaesthesia

  Unfortunately, memory impairment after surgery is not a well-understood phenomenon. We’re just starting to realise the potential long-term effects it can have. 


You can, however, meet with your Anaesthetist before your surgery to discuss the best ways to minimise your risks. Your Anaesthetist will want to discuss your medical history, health habits, and lifestyle. Given this information, your Anaesthetist will be better able to determine how general anaesthesia may effect you and take steps to lower your risk of side effects. If you’re worried or have questions, this meeting is a good time to ask.


  During this time your Anaesthetist may recommend performing a regional anaesthetic as opposed to a general anaesthetic. This involves blocking nerves to one particular area of the body rather than a full general anaesthetic. If this type of anaesthetic appeals to you then the consultation prior to surgery with the Anaesthetist is the best time to discuss this option.


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