Although invasive surgery helps millions of patients live longer each day, it may be linked to cognitive decline, according to a recent study by researchers at the Medical Center.
The study, published in the Feb. issue of the journal Stroke, found that post-operative fever may be connected with the development of measurable cognitive decline in coronary bypass surgery patients.
These fevers, characterized by elevated body temperatures known as hyperthermia, commonly occur in patients who have undergone invasive surgery. Doctors said they still do not know why hyperthermia occurs, but have rarely worried in the past because the fevers are not persistent and disappear relatively quickly.
Dr. Hilary Grocott, associate professor of anesthesiology and lead investigator of the study, said the researchers examined 300 bypass surgery patients. Researchers studied cardiac surgery patients because they typically exhibit symptoms of hyperthermia earlier than patients who have undergone other surgeries.
"[They] were given the day before their bypass operation a battery of neurocognitive tests, including visual-spatial orientation and short-term memory tests. Six weeks after surgery, these tests were administered again," Grocott said.
When doctors conducted tests six weeks after surgery, 39 percent of the patients showed measurable cognitive decline.
Follow-up studies have shown a small, short-term improvement in patients' cognition, but over time, the decline continued and patients showed no signs of improvement.
The longer the surgery and the older the patient, Grocott said, the more pronounced the cognitive decline. In addition, researchers found that the more educated the patient, the less cognitive decline the patient is likely to experience after bypass surgery. "Patients with at least seven years of education are typically associated with less measurable cognitive decline," he said.
Grocott said the research team is now trying to figure out how to prevent hyperthermia from occurring at all. Grocott said one possibility is to actively cool the patient's body after the operation in order to counteract the fever's high temperatures.
He said additional preliminary investigations suggest a genetic link to higher cases of cognitive decline in patients with the E-4 variant of the APOE gene, which is also suspected to play a significant role in the development of Alzheimer's disease.
Grocott said some researchers speculate that hyperthermia occurs because more invasive surgery triggers both an inflammatory response by the immune system and a thermoregulatory response by disrupting brain functions.
Grocott added that although the research has identified the problem, the next step is to find a treatment.
"We don't know what the correct therapy is at present, but identifying that the problem exists is the first step in finding the treatment," he said.
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