Surgeons have long recognized that patients display signs of confusion and mental fog in the days after an operation is performed. This postoperative cognitive dysfunction is very common after heart surgery, but also happens after other sorts of surgery. The impairment almost always clears up in a matter of weeks, though patients over 60 occasionally have long-term issues.
Incidence of dysfunction increases with age and with the complexity and length of the surgery, but there is otherwise no difference between the risk in patients who were under general anesthetic and those who received local. There are some lifestyle connections, as patients who drink a lot or have a lower educational level are at greater risk, though there’s no clear reason educational level should be relevant. The health of the person undergoing an operation—beyond the immediate reason the operation is being performed—also makes a difference; chronically ill patients and people who have had strokes, even if they’ve made a complete recovery, are at greater risk.
It’s not entirely clear what causes this condition. An inflammatory reaction to the operation appears to be partly to blame, particularly in the brain as a result of molecules activated in the body by many surgical procedures. The stress hormone cortisol, produced as a response to surgery, is known to affect a part of the brain that is important in the formation of long-term memory, and fluctuations in cortisol levels have been observed to affect the severity of postoperative cognitive dysfunction, suggesting that the condition is related in some way to cortisol levels.
With the cause being elusive, no successful treatment has been found. However, a team of Swedish researchers think they may have found a possible solution. Compounds called resolvins, which the body manufactures out of omega-3 fatty acids, are known to reduce inflammation, and now there is evidence that they, like anti-inflammatory medications, can lower the incidence of postoperative cognitive dysfunction. In addition, one thing that can increase resolvin production is aspirin—resolvins are part of the process by which aspirin reduces pain. The researchers found that as little as one dose of aspirin helped protect memory in patients after surgery.