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Boston Globe article on ‘pump head’

[No one seems to have a really convincing explanation for the decline in cognition following surgery employing the heart/lung machine.]

http://www.boston.com/news/globe/health_science/articles/2004/09/21/heart_patients_mental_decline_ba...

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Heart patients’ mental decline baffles doctors

By Judy Foreman
September 21, 2004

When Bill Clinton underwent quadruple coronary-bypass surgery on Labor Day, the former president, like most Americans who have similar operations, spent time hooked up to a heart-lung machine while surgeons rerouted blood vessels to his heart.

With luck and his relative youth and health going for him, Clinton, 58, hopefully will rebound in both heart and mind from the surgery, in which doctors replace clogged arteries to the heart with veins and arteries taken from elsewhere in his body.

But many people who go through the procedure -- as 305,000 Americans did in 2001, the latest year for which figures are available -- find that, at least for a few days, often for weeks and sometimes for years afterward, their brains don't work as well as they did before.

Doctors who acknowledge the problem -- and some still pooh-pooh it -- call it post-surgical "neurocognitive deficits." Everybody else calls it "pump head," reflecting the widespread, though unproven, belief that it's the process of blood being pumped through a heart-lung machine while the heart is stopped for surgery that causes small blood clots, air bubbles or other debris to travel to the brain, disrupting memory.

Nobody really knows how common "pump head" is because, outside of research studies, most cardiac patients aren't tested on intellectual function before and after surgery. Detecting all but the most subtle cognitive changes "depends on how hard you look," said Dr. William Cohn, of the Texas Heart Institute in Houston.

Nonetheless, it has been convincingly demonstrated that 80 percent to 90 percent of bypass patients have some cognitive losses when they're discharged from the hospital, Dr. Daniel B. Mark and Dr. Mark F. Newman wrote in a 2002 editorial in the Journal of the American Medical Association.

Even five years after discharge, 42 percent still show measurable cognitive decline, Mark and Newman found in their own study, published in 2001 in the New England Journal of Medicine, though some of this might have been due to normal aging.

In most patients with "pump head," the deficits are real but small. "It's not that you can't solve a problem," Mark said in an interview, "but that you can't solve it as quickly."

Many cardiologists, among them Dr. Christopher Cannon of Brigham and Women's Hospital, also believe that deficits are most likely to occur in older patients who, in addition to having clogged arteries to the heart, may have blockages in blood vessels in the brain as well. In other words, what some see as a consequence of the surgery can be a consequence of the underlying problem of atherosclerosis.

At the moment, there is no cure for "pump head;" nor do doctors understand why some patients get better over time and others do not.

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.
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