This morning I awoke to my local paper online and saw an ad for a local neurosurgery group touting “minimally invasive spine surgery.” That’s interesting because, to me, the minimally invasive moniker should never be used with surgery. Why? No matter how you cut it, by definition, all back surgery is always maximally invasive compared to any injection-based procedures. In that vein, this morning, we’ll review mounting evidence that surgery has been linked to problems with memory and cognition. Why? Because it’s maximally invasive!
Postoperative Delirium or Postoperative Dementia?
While some of us might just experience that typical fuzzy brain feeling after surgery, postoperative delirium and postoperative dementia goes beyond this. Postoperative delirium is recognized by cognitive changes, such as disorientation, confusion, and the inability to process thoughts normally following surgery. It may even be accompanied by agitation or lethargy. In fact, it may not even be apparent immediately after surgery; instead, it may present at some point in the days following surgery.
When there is also cognitive decline after surgery, this is postoperative dementia. Dementia is a neurodegenerative disorder that includes Alzheimer’s disease, diffuse Lewy body disease, vascular dementia, and so on. While dementia can be genetic, environmental exposures can also wreak havoc on our brain cells. And one of those environmental exposures that seems to be doing just that is anesthesia used during surgery.
What We Already Know About the Effect of Anesthesia on Our Brain
Last year I covered a study suggesting that anesthesia during surgery increased the risk of postoperative dementia in 10% of patients. These patients had normal cognitive processing with no dementia prior to surgery. This study group consisted of elderly patients aged 65 and older. In patients who already had dementia prior to surgery, the risk of postoperative dementia, or dementia from surgery, understandably, was even greater.
The links between surgery with general and regional anesthetics and cognitive decline have been well documented. Other studies, in addition to the one mentioned above, have shown that patients who already have or are at a risk dementia are at a greater risk of further cognitive decline following surgery. Patients who already have a disease or health condition (e.g., prior stroke, diabetes, hypertension, etc.) are at an increased risk of developing postoperative dementia. Those with diabetes, for example, had a 60% increased risk of postoperative dementia while those with a prior stroke had four times the risk.
The studies linked above also found higher postoperative dementia risk in patients who had more surgeries. In other words, with each surgery, dementia risk increases. In addition the type of anesthetic used seems to be a factor in dementia risk. For example, the anesthetic isoflurane, especially when used in conjunction with the sleep-inducing agent propofol, has been linked to harmful effects on brain cells, while desflurane hasn’t shown the same toxic effects.
Many studies on postoperative cognitive decline focus more heavily on an elderly population. What about younger patients? Are they immune to anesthesia’s effect on the brain? Today we’re going to look at the risk of postoperative memory decline specifically in the middle-aged population.
Dementia from Surgery? Middle-Aged Patients Also Experience Memory Decline Following Surgery
Building off a previous study that found memory decline in elderly patients (mean age 73) following surgery with anesthesia, the new study set out to investigate the effect of surgery with anesthesia on cognitive processes in a middle-aged (mean age 54) population. The study measured cognitive functions of 964 subjects who had not undergone surgery and then measured the same subjects four years later and every two years after. At that point 312 of the subjects had undergone surgery with anesthesia.
The results? Of those who’d had normal memory measurements at the start of the study, 18% of the surgery patients developed abnormalities in their immediate memory compared to only 10% of the patients who’d not had surgery. In addition greater numbers of surgeries and those lasting for a long period of time seemed to be associated with a greater decrease in memory scores. In other words, the more times a patient receives anesthesia and the longer the patient is under when surgery is performed, the greater the patient’s risk of memory decline. Researchers concluded that surgery with anesthesia in middle-aged patients with normal cognition increases the risk of abnormal memory after surgery.
The upshot? Please get multiple opinions from surgeons and nonsurgeons before you sign up for that big procedure! Memory loss and cognitive changes due to anesthesia are just one of the many risks involved in orthopedic surgery. Many times, we see patients getting surgery who don’t need it or that has been shown in large studies to be no better than a sham procedure. Hence, investigate your options after that first surgeon wants to schedule you for next Tuesday!