Undergoing general anesthesia may cause cognitive decline especially in the elderly. Delirium and postoperative cognitive decline are the two most common untoward effects of surgery. Delirium is transient and obvious but may last days to weeks. Delirium may occur in 10% of postoperative patients. Postoperative cognitive decline is a more long lasting condition, often subtle, and neuropsychological testing is necessary to detect these changes.

One recent study estimates that postoperative cognitive decline occurs in 35% of those under 40, 56% of those 40-59, and 69% of those 60 and older at one week after surgery. By three months the rates decline to about 7% in those under 40, 13% in those 40-59, and 24% of those 60 and older. Another study indicated that about 25% of all surgery patients experience postoperative cognitive decline at one week. Fortunately, this rate drops to about 10% after three months.

Age is clearly a risk factor for postoperative cognitive decline. Other risk factors include cardiopulmonary bypass surgery, duration of anesthesia, respiratory complications, infection, history of alcohol abuse, and a second surgery. Heart surgery produces greater risk for produce postoperative cognitive decline at one week after surgery but is no different from other surgeries (e.g., hip replacement, knee replacement) at three months. Hip or knee replacement produces similar rates of postoperative cognitive decline with either regional or general anesthesia.

Protective factors include education and hypothermic cardiopulmonary surgery. Postoperative cognitive decline is less likely in those with more education. Hypothermic cardiopulmonary bypass surgery reduces the rate of postoperative cognitive decline. So far, studies linking Alzheimer’s disease to anesthesia exposure are contradictory.

The cause of postoperative cognitive decline is unknown. One theory is that those with pre-existing cognitive disorders are at great risk. Other theories suggest possible inflammatory response to surgery or anesthesia induced neurodegeneration. More research needs to be done to clarify the risks of anesthesia and surgery and to tease out possible protective factors.

It is clear that anesthetic agents may be neurotoxic for some and more so after 60. The decision of whether or not to have surgery becomes more complex as we age and needs to weight potential gains and costs. The clearest advice is to avoid purely elective surgical procedures especially in the elderly.