Avoiding Hazards of Bypass Surgery

A study of a new drug that may block the most deadly of the responses to the heart-lung machine during coronary bypass surgery is being conducted by surgeons at the Medical College of Georgia (MCG, Augusta, USA).

The response helps to prevent infection but it can also cause clotting, which results in serious complications in 7-10% of patients. These complications include injury of the lung or kidney and heart attack or stroke. Children are at special risk, especially those with complex heart defects who spend hours or even days on the heart-lung machine.

"It's a massive physiologic insult like a major trauma, so our body comes alive with an inflammatory response to circulating through this unit,” explained Dr. Landolfo, chief of the MCG section of cardiothoracic surgery.

MCG is participating in a study of 5,000 heart bypass patients in about 40 states and three foreign countries that includes at-risk patients such as those who have had a previous stroke or heart attack or have diabetes. The purpose is to determine whether giving the complement blocker pexelizumab intravenously before, during, and after bypass can block the worst aspect of the inflammatory response. Women can be of risk simply because their smaller size causes their blood to pass through the machine more times. Children with low oxygen levels before surgery may have trouble activating a natural mechanism that could correct some cell damage caused by bypass surgery.

Surgeons at MCG are measuring levels of a surface receptor called CD 163 in newborns before, during, and after surgery and looking at the expression of macrophages in heart tissue. They are also looking at the complement system activated by bypass, which in children can cause leaking of endothelial cells, and at expression of factors that regulate immunity, such as NFkappaBeta.

"We are pretty good at having patients survive, but it's all the morbidity related to heart surgery. Much of what remains is related to the heart-lung machine,” observed Dr. Landolfo.




Related Links:
Medical College of Georgia