For Some Patients, Surgery Carries Risk of Cognitive Dysfunction

Thousands of surgeries requiring general anesthesia are performed every day in the United States, and most are highly successful, with no major side effects or complications. But as any medical practitioner will tell you, no surgery is without some risk, especially as we age.

For older patients, side effects can involve a loss of cognitive function - the ability to perceive and be aware of their surroundings, and use reasoning, judgment, intuition and memory, among other mental processes. In October 2004, at the annual meeting of the American Society of Anesthesiologists, Duke University researchers presented a study of 354 surgical patients 60 and older that found that 59% experienced cognitive declines when they were discharged from the hospital. Three months later, many of those patients recovered their mental functions, and the percentage of those affected was down to 34%. In 1999, the British medical journal The Lancet published a similar study, in which 25% of older patients had symptoms of cognitive dysfunction at discharge; three months later, the percentage with lingering side effects was less than 10%.

M. Saeed Dhamee, MD, Professor of Anesthesiology at the Medical College of Wisconsin, says the loss of cognitive function does seem to occur most frequently among older patients, especially those who have undergone heart surgery, joint replacements or fracture repairs. These types of surgeries, which require that a patient be anesthetized for two hours or more, tend to be more common among older people.

"The number is fairly significant during the first six weeks after surgery," he says. "Three months later, the percentage affected goes down, and by one year post-operatively, very few are still affected."

Who's at Risk?
A patient's risk for post-operative cognitive dysfunction depends on his or her overall health and lifestyle habits, as well the type of anesthesia used and the patient's response to it, Dr. Dhamee says. He notes that many of the patients who lose cognitive function after surgery are those who have already experienced memory problems or other cognitive deficits before the procedure.

Also at risk are patients who smoke and those who drink alcohol excessively. "We're not talking about patients who drink in moderation," he says. In fact, he adds, medical research shows a daily drink of alcohol may actually have some health benefits.

Dr. Dhamee added that smoking and excessive alcohol use can damage the heart, lungs, liver and kidneys. "In fact, these substances can affect vital organ function and blood flow as strongly as prescription drugs, and consumption of any of these substances can change the way an anesthetic drug will work during surgery."

Notify Anesthesiologist Before Surgery
Because of how cigarettes or alcohol can affect organ function, it is crucial for patients to tell their anesthesiologist about their consumption of these substances, as well as all prescription and over-the-counter drugs they use. The same warning applies to users of so-called "street drugs" - marijuana, cocaine or amphetamines, among others. Patients should also disclose which herbal medications they use, because some herbals can also influence the effects of anesthesia.

"If we know that patients smoke or consume drugs or alcohol, we can give them medications before, during and after surgery to offset some of the side effects," Dr. Dhamee says. "It's a very complicated affair, but the risks are reduced if we know their baseline conditions."

Patients who fail to disclose their drug or alcohol consumption may experience the symptoms of alcohol or drug withdrawal after surgery. Alcohol withdrawal, for example, can make patients anxious and, in some cases, panicky. Some patients experience sleeplessness, sweating, poor appetite, tremors or "the shakes," convulsions, hallucinations and, in serious cases, seizures or even death.

Other conditions that raise a patient's risks during surgery include hypertension and heart disease, both of which are more prevalent with age. "Our arteries become harder, and that makes blood flow less efficient," Dr. Dhamee says. In severe cases, reduced blood flow can lead to cerebral complications.

Dr. Dhamee said that the duration of the surgery should not have a significant impact on a patient's risk for side effects, because patients are closely monitored by the anesthesiologist throughout the procedure. The effects of the drugs used during anesthesia typically leave the body within 24 to 48 hours, he said.

Cause Still Unknown
Although physicians can help their patients avert cognitive dysfunction by knowing their health history and the drugs or substances they ingest, the reason some patients experience loss of cognitive function is not widely understood, Dr. Dhamee says. "We are looking to the patient to help us prevent this outcome, but we still must find the cause factor."

Scientists from a variety of disciplines are studying the phenomenon, he says, including psychologists, surgeons and anesthesiologists. Some are analyzing the problem by way of genetics; others are exploring the levels of abnormal proteins found in the patient as a possible cause. For some patients, suffering anxiety and stress before surgery can also trigger reactions during surgery that can predispose them to cognitive decline and other side effects, Dr. Dhamee says.

Families of patients who might be at risk for cognitive dysfunction can also play a role, Dr Dhamee advises: "Families must be alert to the problem and promptly notify doctors and nurses if they recognize a change in their loved one's behavior after surgery. That way, we can intervene earlier."

Barbara Abel
HealthLink Contributing Writer

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.