Wake Forest Team Reduces Brain Deficits After Coronary Artery Bypass Surgery

May 12, 1998

WASHINGTON, DC -- Controlling unnecessary manipulation of the heart and the aorta during coronary artery bypass surgery dramatically reduces the number of patients with major neuropsychological deficits after surgery, a Wake Forest University Baptist Medical Center researcher told a Washington conference today.

David Stump Ph.D., research associate professor of anesthesiology and neurology, said a multi-disciplinary team has cut the number of emboli detected during surgery by 15 to 20 percent and reduced the patients experiencing confusion, memory loss and personality changes.

They also have halved the number of patients suffering stroke and other acute complications when compared to the results from coronary artery bypass teams across the country.

Stump said the key to the change is ultrasonic monitoring of blood vessels for detectable emboli that can lead directly to neurologic deficits.

"At this point, we know that ultrasonically detectable emboli mainly come from the surgical field," said Stump. "By modifying surgical technique, we can get a 15 to 20 percent reduction in emboli and a 50 percent reduction in patients with major neuropsychological complaints."

And now the team is testing various neuroprotective drugs that may further cut post-surgery brain deficits. He described one man who had more than 1,500 emboli over a short period of time who was still well enough to go home in 2? days. "We had predicted based on our previous results that the man would have some significant problems."

Stump's comments came as part of a symposium on embolism detection at a Washington meeting of the Space and Underwater Research Group of the World Federation of Neurology. The meeting is being coordinated by the Stroke Research Center of the Wake Forest University Baptist Medical Center.

Stump said surgeons at the Wake Forest University Baptist Medical Center have made their dramatic strides in reducing post-surgical brain deficits by changing the way they clamp the aorta and by reducing manipulation of the aorta and of the heart itself.

They monitor the production of emboli by using ultrasound monitors on the carotid arteries that supply blood to the brain. The ultrasound probes pick up the debris as it is passing by.

"Our surgeons have actively pursued new surgical methods to reduce the number of emboli," Stump said.

The research team is now looking into a second kind of emboli -- what he calls microemboli, which are particles of lipids, blood fats. Some of these emboli also may be related to surgical technique and to use of the heart-lung machine.

Researchers don't know as much about them. "We have animal data that suggests that there are important changes," Stump said.

Unlike the larger, debris-caused emboli, changes in the brain from the microemboli were not observable on Magnetic Resonance Imaging, MRI. "But on MRS, magnetic resonance spectroscopy, you can see there are large changes on the side of the pig brain that is embolized with small particulate matter that is the same size as the microemboli we see in humans."

The microemboli also trigger production of another defensive mechanism -- heat shock or stress protein. What they find are small areas of the brain that don't get enough oxygen, and small areas of brain tissue death.

"We don't know exactly what this means but this can't be good for you," said Stump, who is a neuropsychologist.

However, Stump said, 50 percent of the people who are sick enough to need coronary artery bypass surgery already have brain damage. "They have MRI changes that are abnormal and are evidence of previous brain injury."

These are called silent ischemic infarcts. The Framingham Heart study documented that about 10 percent of 60-year-old white males are walking around with these infarcts, he said. But these deficits are far higher in people with heart disease.

"As a neuropsychologist, I can tell you that you can demonstrate deficits in almost all of these patients with a very brief battery of tests. You can quickly tell that they're having some word finding and memory dysfunction. But to the average layman, or untrained physician, they are silent."

The coronary artery bypass surgery also provides a good test arena for neuroprotective drugs "because it is one of the few instances when you can really get a baseline prior to surgery," and compare it to the results after the surgery is completed.

"What you find is that most of these patients have pretty significant brain swelling immediately after surgery," he said. The drugs apparently prevent the swelling.

But these drugs "may have a much greater impact on people with acute brain injury, cardiac arrest or transient ischemic attacks." The drugs may able to ward off such lasting effects.

The four-day meeting -- the Congress on Cerebral Ischemia, Vascular Dementia, Epilepsy and CNS Injury: New Aspects of Prevention and Treatment from Space and Underwater Exploration -- continues through Wednesday noon at the Washington Marriott Wardman Park Hotel, formerly the Sheraton Washington.
-end-


Wake Forest Baptist Medical Center

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