Surgery & Cognition
Patient education about postoperative cognitive risks is essential.
Older adults, having known someone whose memory wasn't quite the same following surgery, may have legitimate fears about cognitive decline after a procedure. As a result, they may feel uneasy when faced with having to undergo surgery.
While a considerable amount of research has addressed this issue, there's still debate about whether memory impairment stems from anesthesia, the surgery itself, or other compounding factors. Until more is known, it's essential that health care professionals educate both patients and their caregivers about the surgery and its potential impact on cognitive decline, and ensure steps are taken to prevent cognitive effects, and recognize and address those that do arise.
Does Surgery Result in Cognitive Decline?
The researchers used resources from the ongoing Mayo Clinic Study of Aging, a long-term epidemiologic and population-based prospective study about cognitive changes related to aging. Participants in Olmsted County, Minnesota, undergo cognitive assessments at roughly 15-month intervals. The researchers reviewed records from 1,819 participants, aged 70 to 89 at the time of study enrollment.
The researchers analyzed whether exposure to surgery and anesthesia during the period 20 years before enrollment was associated with cognitive decline and whether exposure to anesthesia after study enrollment by older adults was associated with a cognitive change. While older adults often experience cognitive decline as part of the normal aging process, decline following exposure to anesthesia and surgery was found to be slightly accelerated beyond that associated with normal aging.
Although the decline in brain function observed in the Mayo Clinic research was small, it could be meaningful for individuals with already low cognitive function or preexisting mild cognitive impairment who are considering surgery with general anesthesia, says Juraj Sprung, MD, PhD, a Mayo Clinic anesthesiologist and the study's lead author. It's a good reason, he says, to better inform patients about their risks.
While providers agree that patient education is key, many are still trying to understand exactly how surgery and anesthesia may affect their patients' cognition. Lee Fleisher, MD, chair of anesthesiology and critical care at the University of Pennsylvania, in Philadelphia, has been part of an ongoing effort to better understand anesthesia and its effect on the brain. As chair of the American Society of Anesthesiologists' (ASA) Ad Hoc Committee for the Perioperative Brain Health Initiative (a patient safety initiative), he's been an advocate for better meeting the needs of older patients undergoing surgery.
"This is something that we still do not fully understand but believe that research is critical," Fleisher says. "Some patients describe their postoperative cognitive abilities as 'brain fog.' Their memory isn't as sharp. And for some patients this may go on for more than a day. It's generally said that forgetfulness can go on for as long as three months, but I interviewed a patient who experienced it for four and a half months. She described problems with the speed of recalling information or about forgetting details or even a conversation she had with her son. She said that her social circle told her that her Bridge game wasn't the same. This eventually corrected itself, but with patients who were already experiencing a decline, there's a concern about whether surgery will accelerate it. When the patients do recover, they may be at a lower baseline cognitively than where they started."
As evidence accumulates about the association, he says, providers need to inform older patients about the possibility that exposure may result in cognitive impairment, just as they'd ensure informed consent for transfusions or potential complications of other treatments.
Sprung adds that the study did not elicit whether the association between surgery and cognitive decline was related to surgery, exposure to anesthesia, both, or perhaps even underlying comorbidities. Even so, he believes that preoperative cognitive testing may help assess the level of cognitive functioning in an individual, and, therefore may help to determine who is at an increased risk of postoperative cognitive impairment.
"For the majority of elderly individuals with a higher level of mental functioning, this decline in cognition associated with exposure to surgery and anesthesia is small and would likely not be noticed during their lifetimes," Sprung says. "However, in adults with preexisting borderline low cognitive reserve clinically undetectable at the time of their surgery, exposure to anesthesia and surgery may result in unmasking of the underlying cognitive deficit." Therefore, he says, older adults considering elective surgery should be advised of the risk so they can be allowed to determine whether they want to proceed.
Of course, there's a big difference between acute memory loss and cognitive decline that's permanent, says Frederick Sieber, MD, a professor of anesthesiology and critical care medicine at the Johns Hopkins University School of Medicine. It's important, he says, to educate patients about all possible risks, explaining that acute memory loss is much more likely than a long-term effect.
"When counseling patients, providers should make clear that acute memory loss, such as difficulty thinking, is pretty common immediately following surgery," Sieber says. "Even younger patients deal with acute memory loss, and people with relatively intact cognitive functioning generally experience limited periods of cognitive decline. However, there's a certain percentage for whom that decline does become permanent. Even though it's the exception, patients should still be advised of the risk."
Looking at Postoperative Delirium
According to the Initiative, postoperative delirium is thought to be one of the most common postoperative complications in older adults, with incidence rates ranging from 5% to 15%. However, with certain high-risk groups, such as patients with a hip fracture, the range can be between 16% to 62%.
The cause of postoperative delirium is unknown. There's uncertainty about whether the type or the dosing of anesthesia might be a contributing factor to the condition. Sieber led a study of 200 men and women designed to determine whether reducing the amount of anesthesia reduces the risk of postoperative delirium in older patients. While the study, published in JAMA Surgery, found that lighter sedation failed to reduce risks of delirium in severely ill people undergoing hip fracture repair, it indicated that for those in relatively better health, deep sedation more than doubled the risk of postoperative delirium compared with light sedation.
Although they were contrary to what was expected, Sieber says, "These findings add to growing evidence that clinicians must match sedation levels to each patient's health—especially in the management of older surgical patients—and must work to optimize each person's health before surgery, if possible, especially those with heart and blood vessel disease and with diabetes."
Sieber says that the study's take-home message for providers is that it's important to assess patients preoperatively for comorbidities, since underlying disease, particularly cardiovascular disease, is a major contributor to postoperative delirium. For patients in relatively good health but at a risk for postoperative delirium, Sieber suggests the use of light sedation for those having a spinal anesthetic, when possible, in order to keep their risk low.
But anesthesia may not be the only issue. Fleisher says it's likely postoperative delirium is also related to drugs utilized after surgery or to other compounding factors such as lack of sleep or stress prior to the procedure.
"If you've ever pulled an all-nighter, you understand how that experience can be disorienting," he explains. "When patients have an upcoming major surgery scheduled, they're often under a lot of stress and not getting a full night's sleep. Those circumstances can compound and potentially contribute to postoperative delirium."
Sieber adds that there are simple, nonpharmacological steps that can be taken to minimize the risk of postoperative delirium, including the following:
• making sure the patients' pain is adequately treated;
• encouraging patients to get up and move as soon as possible;
• ensuring that patients have their hearing aids and glasses as soon as possible after surgery;
• ensuring that family members are present after surgery to help orient patients;
• providing patients with a hospital bed near a window so that they can tell night from day; and
• ensuring prior to surgery that patients' medication regimens will not provoke delirium.
"These are simple measures that have been shown to go a long way in preventing delirium," Sieber says. "This is important, as delirium can lead to bigger concerns if it's not addressed."
Research has indicated that postoperative delirium can go unrecognized or unaddressed by health care staff. This is problematic, as research also indicates that unrecognized delirium in older adults results in poor outcomes, including complications during hospitalization, increased length of stay, nursing home placement, or even death.
"Things can quickly spiral out of control for the patients and their care teams. That's why it's so important for everyone to be prepared and to ensure these simple preventive steps are taken to hopefully minimize or even eliminate the risk," Sieber says.
Equally important is that all providers and staff members are alert to cognitive issues that do occur postoperatively. "While I would argue that geriatricians are well aware of the potential effects of surgery on cognition, nongeriatricians are not always educated on this," Fleisher adds. "In fact, we have even heard stories of people who have gotten work-ups for a stroke following surgery when they were actually experiencing delayed cognitive recovery. This emphasizes how important it is that more people—providers and patients—are made aware that this is a possibility."
"I also think that family members should be made more aware of their role in a patient's recovery process," Fleisher adds. "The simple things that they can do to help improve immediate recovery—such as being present to answer questions and making sure the patients have their glasses or hearing aids—make a really big difference. Family members are very important ambassadors for older adults who are undergoing surgery. They can be a vital piece of their postsurgical success."
While discussing cognitive decline may intimidate patients, Deiner says that it's important to bear in mind that the efforts to better understand what's happening should feel empowering—not "all bad news."
"The fact is, older adults are doing better than ever, and we're really good at getting people through surgery," Deiner says. "We're constantly looking at ways we can improve how we get older adults back to their best function—mentally and physically. We've come a very long way, and the fact that there's so much engagement in this issue is a testament that our expectations for surgical recovery continue to grow. Older adults are having surgery and returning to activities of normal daily living—including going back to work—faster and better than ever before. At the end of the day, it's about taking ownership of the healing process. The better informed our patients are, the better their recovery will prove to be."
— Lindsey Getz is an award-winning freelance writer based in Royersford, Pennsylvania.