General Anesthetics and Dementia-Do You Know Which One is Less Likely to Fry Your Brain?

Is there a link between the use of general anesthetics and dementia risk?  General anesthesia is the type where they put a patient to sleep with a tube in the throat. This topic has a personal interest for me as my father started a serious cognitive decline after hip surgery, so I’ve always wondered if there was a known link.

Now scientists in Taiwan have published on a large group of patients where the sicker patients exposed to more anesthesia have higher risks of later dementia. They took more than five thousand dementia patients and compared their surgical histories to more than 21,000 patients without dementia. The patients who were exposed to general anesthesia had a 35% increased risk for dementia whereas surgery under heavy sedation wasn’t associated with such a risk. Sicker patients fared worse, with about a 60% increased risk for patients who had diabetes and anesthesia and almost a doubling of risk for those with high blood pressure. The patients with a prior stroke had almost a quadrupling of risk! All of the risk was dose dependent; meaning that more surgeries for an individual translated into more risk. Is this an isolated paper, or is there more evidence that general anesthesia is linked to dementia?

On the other side of the fence, a much smaller Mayo clinic study of just under 1,000 patients in each group didn’t find this same risk. However, neither study identifies the general anesthetics used. Could this be a confounder? For example, a 2012 study suggests that the bad brain effects could be linked to the type of general anesthesia. For example, Isoflurane was associated with dementia markers in the spinal fluid 24 hours surgery, but another commonly used general anesthetic (desflurane) wasn’t associated with the same markers. When a lab study looked at the effects of these two anesthetics on brain cells, they again found that isoflurane caused harm to these cells, but not desflurane. A recent lab and animal study found that the most common induction agent (used to initiate a patient going to sleep), propofol, makes the bad brain cell effects of isoflurane worse. In my literature review this morning, I was astounded by the intense publishing activity on this topic with many authors very concerned about these emerging risks.

The upshot? Isoflurane looks like a bad actor when it comes to damaging brain cells, much the same way that the local anesthetic marcaine is with damaging cartilage cells. The first rule for my patients, is always to avoid surgery where possible, so this rule is certainly strengthened by these recent studies showing a link between general anesthetics and dementia. So for example, try non-surgical options before you sign up for that hip or knee replacement. However, if you have to undergo general anesthesia, based on what’s published at the moment, I personally would request that you avoid isoflurane and instead ask for desflurane. You should also note that another type of common general anesthetic (sevoflurane) also seems to have issues. Finally, the gestalt of my research review this morning seems to show that any type of general anesthesia may have more impact if the patient is already at risk for or has dementia. 

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