General Anesthesia May Unmask Hidden Cognitive Decline

A new study links surgery and cognitive decline.

Posted Oct 11, 2018

A very well-executed study published in the Journal of Alzheimer’s Disease (2018; 62(1):319-333. doi:10.3233/JAD-170496) has shown that certain individuals demonstrate a significant decline in their mental abilities following surgery requiring general anesthesia, in this case, for total knee arthroplasty (knee replacement surgery).

Post-Surgery Cognitive Decline

Those most at risk for a post-surgical decline in cognitive abilities showed:

a) Slow processing speed (thinking and reaction speed),

b) Reduced working memory (short-term memory), for example, the ability to hold information in one’s mind and manipulate it. This skill is used in such things as adding and subtracting numbers (multiple numbers).

c) Reduction of brain size (measured by increased lateral ventricle size)

Red Alert

The study raises a 'red-alert' and indicates it is necessary to screen those who are over 60 (or perhaps younger if there is a known family history of dementia, traumatic brain injury, strokes, and perhaps other chronic medical conditions) who are considering major surgery. This can be done using some simple neuropsychological tests, such as the CNS Vital Signs test we use in our office, as well as a pre-op MRI to assess brain volume (ventricular volume).

Study Limitations

The limitations of this study were that there was only one post-surgical measurement after surgery. It is possible that the cognitive decline will have reversed several months later; alternatively, it may have continued to progress. Additionally, the control group had a higher level of cognitive function than those who underwent surgery, even before the surgery. The authors speculate that this is possibly due to the fact that those who had surgery had lived a life with limited exercise and activity. It is also possible that the compromised brain may be part of the pain syndrome itself. Finally, while the authors claim to have controlled for the effect of post-surgical pain medication, it is not clear (to me) that factor can fully be disregarded.

Consistent with My Clinical Experience

This study is consistent with my clinical experience. In 1983, one of my first patients was a 70-ish-year-old woman who developed new onset depression, after her heart bypass surgery. This was clearly the result of the surgery (now known to occur in up to 50% of those who go on the bypass pump during heart surgery), as it was not present until a few days post-op. It responded partially to lithium, but Ms. L. was never again fully free of depression. Most recently, a vibrant 76-year-old woman with a family history of dementia declined precipitously after 5 elective surgical procedures in one year—including a bilateral knee replacement surgery. In all likelihood, a simmering dementia was unmasked by the repetitive general anesthesia.

The Take Away

General Anesthesia is not to be taken lightly, and those who are older, or at risk for dementia need to be pre-screened to assess the risk of adverse cognitive consequences of surgery.

References

Journal of Alzheimer’s Disease (2018; 62(1):319-333. doi:10.3233/JAD-170496)