Targeting Toxins After Cardiac Surgery

Antibodies crucial to protect kidneys, says study

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By
HealthDay Reporter

TUESDAY, Oct. 16, 2001 (HealthDayNews) -- Bacterial poisons that find their way into the bloodstream during heart surgery may damage the kidneys in a small percentage of patients, says a new study.

Increasing the antibodies that fight these toxins may be vital to protect the kidneys after bypass surgery, say doctors from Duke University Medical Center in Durham, N.C. They presented their findings today at the annual meeting of the American Society of Anesthesiologists in New Orleans.

Their study looked at whether levels of endotoxin core antibodies, or IgM EndoCAb, were linked to kidney complications after coronary artery bypass surgery. Roughly 8 percent of patients who have the procedure to reroute blood around clogged arteries in the heart have kidney damage after the surgery.

"The … endotoxin is something that a lot of bacteria generate," says lead author Dr. Mark Stafford-Smith. "When it gets released during an infection into the body, it causes a lot of harm, including triggering the immune, or inflammatory response."

Doctors think the gastrointestinal tract becomes "leaky" during cardiac surgery, allowing toxins from bacteria normally confined to the bowels to enter the bloodstream, Stafford-Smith says. "This would potentially trigger this inflammatory response, which is recognized to be a problem during heart surgery, and that may be one of the reasons why the kidney is being injured."

These complications usually are temporary, but in 2 percent of cases, patients require kidney dialysis, and up to 61 percent of those patients will die.

Led by Stafford-Smith, an associate professor of anesthesiology, the researchers measured blood IgM EndoCAb levels in 461 patients before cardiac surgery. After the procedure, they measured levels of blood creatinine, a byproduct of normal metabolism. Doctors watch creatinine levels after surgery because an increase points to a problem with kidney function.

Patients were separated into two groups: 182 with high blood IgM EndoCAb levels and 279 with low levels. After surgery, patients with high IgM EndoCAb levels showed an average 20.9 percent increase in creatinine levels, while patients with low IgM EndoCAb levels saw creatinine levels spike 31.3 percent.

Stafford-Smith says the findings suggest that therapies that would increase IgM EndoCAb levels before surgery may reduce the chance of kidney problems after the procedure.

"Any treatments that have ever been tried, including some that are even currently in use, have never really been shown to improve outcome," says Stafford-Smith. "This gives us some new avenue to explore where we may be able to find some approach which might protect the kidneys and maybe improve people's overall outcome from heart surgery."

The options could include a vaccine that increases IgM EndoCAb levels before surgery or drugs that neutralize endotoxins, he says.

Dr. Vincent Dennis, chairman of nephrology and hypertension at the Cleveland Clinic in Cleveland, Ohio, says patients often don't have kidney failure or need long-term dialysis after open-heart surgery. But, he says there are no real treatments for kidney dysfunction following heart surgery.

"If 2 percent of people undergoing open-heart surgery develop acute renal failure, and if the mortality rate of those 2 percent is 60 times [higher than those who don't develop kidney failure] … anything that would ameliorate that situation would certainly have a profound effect on the 2 percent of patients who are at risk," says Dennis.

What To Do

Check this primer on kidney function from the National Institute of Diabetes and Digestive and Kidney Diseases.

You can also read about coronary artery bypass surgery or other procedures at YourSurgery.com or the American Heart Association Web site.

SOURCES: Interviews with Mark Stafford Smith, M.D., associate professor, division of cardiac anesthesiology, department of anesthesiology, Duke University Medical Center, Durham, N.C., and Vincent W. Dennis, M.D., chairman, department of nephrology and hypertension, Cleveland Clinic, Cleveland, Ohio; abstract, annual meeting American Society of Anesthesiologists, New Orleans, La.

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