A number of studies in recent years have found that up to half of patients who undergo the surgery that former President Clinton recently had have problems with attention, memory and the ability to carry out several tasks at the same time.
These post-bypass cognitive problems have become a focus of surgeons' attention: Some say the risk for memory and attention deficits increases in patients who are put on heart-lung machines during the surgery _ that stopping the heart plays a role in subsequent cognitive problems.
More than 80 percent of bypass surgeries, including Clinton's, use a heart-lung machine. The machine does the work of the heart and lungs during surgery.
It's possible that such post-bypass problems result from anesthesia or even the time spent in a hospital environment and that only a keen neuropsychologist could identify such a deficit, said Irvin B. Krukenkamp, chief of cardiothoracic surgery and director of the Heart Center at Stony Brook University Hospital, Stony Brook, N.Y.
A study three years ago showed that more than half of 261 patients who had bypass surgery and used a heart-lung machine experienced serious cognitive declines. Dr. Mark Newman, chairman of anesthesiology at Duke University Medical Center in Durham, N.C., and his colleagues found that six weeks later, 36 percent of patients still had problems. Six months after surgery, one in five was still impaired.
They re-examined patients five years later and found that 42 percent had cognitive problems not present before surgery. Those most at risk had shown decline after surgery, Newman said. He acknowledged that the patients were older and thus at higher risk.
Since 1998, surgeons have had the option of using a technique that doesn't require stopping the heart or lungs. In this off-pump technique, surgeons use a fork-like device to stabilize the artery, then wrap small rubber bands around it to stop blood flow. Most surgeons agree that the heart-lung machine leads to a better surgical outcome, though there are indications that the off-pump procedure could reduce the cognitive complications.
"It's really not known yet whether one technique is better for the brain than another," Newman said. Such a determination requires a large-scale study, he said.