Heart patients? mental decline baffles doctors
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Though it's not clear today that the heart-lung machine is the real culprit in "pump head," many doctors for years assumed it was and focused their prevention efforts on the machine itself.
One way has been to keep improving the technology. Older heart-lung machines were crude, said Dr. Irv Kron, chairman of the department of surgery at the University of Virginia. "There were no filters, the technology was terrible," allowing "particulate matter" to flow to the brain.
Now, the inside of the machine's tubing has been coated to reduce the body's inflammatory response. Before, blood cells were getting damaged when they were bumped along through the tubing, and may have caused some of the cognitive problems,said Dr. William Baumgartner, chief of cardiac surgery at Johns Hopkins Hospital.
Better yet, some doctors argue, would be to get rid of the pumps and operate on still-beating hearts using special devices, including one invented by Cohn, to stabilize just one part of the heart at a time.
But off-pump surgery, though it has been growing in recent years, is still only used in about 22 percent of bypass procedures, said Dr. John Puskas, an associate professor of surgery at Emory University in Atlanta. "I think it's clear that off-pump is better, but proving it with scientific rigor is challenging," he said. In general, off-pump patients leave the hospital one day sooner and have less blood loss.
A study by Dutch researchers in 2002 found that, although the off-pump group had better cognitive outcomes right after surgery, by one year later, the difference was negligible.
Puskas's own, still-unpublished, analysis also shows mixed results. Among three trials looking at cognitive deficits two weeks after surgery, two found off-pump patients did better and one found no difference. In four trials that looked at patients up to six months after surgery, significantly fewer patients had cognitive dysfunction in the off-pump group. But in four other trials looking at patients one year after surgery, there was no difference between the groups.
Other doctors question how valuable off-pump surgery is because, despite the name, "pump head" can occur even after operations in which heart-lung machines are not used at all -- perhaps because of the stress of surgery, the duration of anesthesia, postoperative infections or respiratory problems. One study of 262 older patients who had knee-replacement surgery found that 5 percent had cognitive dysfunction six months after surgery.
At Johns Hopkins, Baumgartner's team compared patients who had on-pump bypass surgery to equally sick coronary-artery-disease patients who did not have bypass surgery. One year later, there was no difference in cognitive function between the two groups. In general, off-pump patients leave the hospital a day sooner, and have less blood loss, and may have fewer kidney problems.
On the other hand, in off-pump procedures, it's harder for the surgeon to attach new blood vessels.
So, how should surgeons decide which surgery is best for a given patient?
"Nobody really knows at this point," said Dr. Fardad Esmailian, a cardiac surgeon at the David Geffen School of Medicine at UCLA.
But patients can at least take heart from the fact that many cardiologists, including Dr. Frank Sellke, chief of cardiothoracic surgery at Beth Israel Deaconess Medical Center, believe the operations are "fairly equivalent."
In other words, pick a surgeon you feel comfortable with and go with that surgeon's preferred procedure.
Judy Foreman is a freelance columnist who can be contacted at email@example.com.
© Copyright 2004 Globe Newspaper Company.