Heart-Lung Pump Gets Small Reprieve
Brain damage after bypass not all linked to life-support, study finds
TUESDAY, March 19, 2002 (HealthDayNews) -- Coronary bypass surgery, although life-saving, has been shadowed by evidence that a sizeable fraction of patients don't feel quite "right" in the head afterward.
Doctors have blamed this slight brain damage on the machines surgeons use to keep their patients alive on the operating table while they stall the beating heart long enough to reroute the blood supply.
But a new study by Dutch researchers has found that patients who undergo bypass surgery that avoids heart-lung machines are only somewhat less likely in the short run to suffer brain damage than those on the pumps. Even that modest difference wanes over time, and after a year is effectively undetectable.
"It's not only the heart-lung machine which causes cognitive decline after cardiac surgery," said the study's lead author, Dr. Diederik Van Dijk, an anesthesiologist at University Medical Center in Utrecht, Netherlands.
"It could mean the problem is smaller than we think, but other factors may be causing" the subtle brain injury, he added. These might include the trauma of major surgery, the effects of general anesthesia, or other yet unknown factors.
Heart experts cautioned that the Dutch results, which appear in tomorrow's Journal of the American Medical Association, might not be entirely applicable to the United States. Bypass graft recipients here are typically older and sicker than those in the European study, and off-pump surgery might have a bigger impact in this country.
However, they said, this work and other reports of cognitive loss associated with bypass indicate that the complication remains poorly understood.
"Clearly the pump does have some effect, but not nearly as much as these other studies have indicated," said Dr. Irving Kron, chief of surgery at the University of Virginia Medical Center in Charlottesville, who was familiar with the latest findings.
Other factors, including a patient's age, how hard the arteries are, and small clots that break off while surgeons manipulate vessels, may help explain the cognitive declines, Kron said.
Some doctors have suggested that the blood pressure delivered by heart-lung machines may be improperly calibrated for older adult patients. Kron said that's a possibility, and added that the pumps don't provide pulsing blood flow, which may be important for keeping the brain adequately nourished.
More than 800,000 people worldwide have cardiac bypass operations, in which stretches of blood vessels from other parts of the body are used to restore blood flow around clogged portions of coronary arteries. Most will be put on a heart-lung machine, although the proportion of so-called "off-pump" procedures is rising.
In the new study, Van Dijk and his colleagues compared cognitive outcomes in 281 people, mostly men, with coronary artery disease who had undergone bypass surgery for the first time. Of those, 142 were treated off-pump and 139 had the aid of a heart-lung machine. [About 12 percent of the people didn't complete the study.]
The researchers tested the patients' cognitive function -- 10 tests including motor skills, verbal and working memory, attention and other common measures -- both before surgery and again at three months and 12 months after the operation. Evidence of cognitive loss was considered to be at least a 20 percent drop from baseline in at least 20 percent of the categories.
The researchers also compared rates of strokes, overall mortality and quality of life outcomes in the two groups.
At the first follow-up, the patients who underwent off-pump bypass appeared somewhat less likely to have suffered brain damage than those supported by heart-lung machines. But by 12 months, the risk in either group was essentially the same.
"Patients who received their first [bypass] surgery without [heart-lung help] had improved cognitive outcomes three months after the procedure, but the effects were limited and became negligible at 12 months," the researchers write.
However, cognitive decline in both groups increased with time, even as the split between the two groups narrowed. By the end of the study, approximately 30 percent of the people overall had evidence of brain damage, a percentage not considered out of line with previous findings.
People in both groups showed improvement in quality of life, especially at the three-month evaluation. Two people in the on-pump group and one in the off-pump group had a stroke within a year of surgery; two patients in each group died during the follow-up period, the researchers said.
What To Do
So what if you're confronting bypass surgery? Van Dijk said he would recommend off-pump procedures for relatively simple operations, such as one or two grafts at the front side of the heart, and on-pump surgery for more complicated cases. But for the elderly, who are at significantly increased risk of stroke, "I would strongly prefer off-pump," he said.
To find out more about bypass surgery, try the Texas Heart Institute.