Filtration aids cardiac surgery outcomes

Studies find filtration works for adults, infants

The roughly 20,000 children and more than 200,000 older Americans who undergo cardiac surgery each year in the United States may soon experience less tissue damage and faster recoveries. Infants undergoing cardiac surgery experienced fewer complications when white blood cells were filtered out of the blood, according to a recent study in the Annals of Thoracic Surgery.

In the study, 28 infants ages four days to 37 months underwent open-heart surgery with the use of a heart-lung machine. Doctors found that the production of destructive oxygen free radicals associated with tissue damage to the heart and lungs of cardiac surgery patients was significantly reduced when white blood cells were filtered from the blood.

"Our study shows that reoxygenation injury can be limited by decreasing the oxygen concentration of blood in the heart-lung machine, or more effectively, by filtration," says Bradley Allen, MD, assistant professor of surgery at the University of Illinois at Chicago Medical Center. "We found that leukocyte reduction by filtration resulted in the lowest production of damaging oxygen free radicals."

Allen and his colleagues actually filter white cells out of the blood twice. "Because young children have such low blood volume, we have to prime the heart-lung machine with donor blood prior to surgery," he explains. "We actually filter the donor blood prior to surgery. Another filter in the bypass circuit filters white cells out of blood coming from the child."

Infants in the study spent less time on the ventilator and in the intensive care unit and had a decreased need for potent drugs, Allen says.

"We believe those factors combined should improve outcomes, reduce costs, and get the infants back together with their parents sooner. These kids definitely have a better post-operative course. They are less swollen and do better in every way post-operatively," he explains. (For additional information on the leukocyte filtration technique, see Allen’s animal study in the Journal of Thoracic Cardiovascular Surgery.2)

Evidence from clinical studies of adult patients not only supports Allen’s research findings but shows cost savings in the range of $2,000 to $6,000 per patient. In a study of 400 adults undergoing open-heart surgery, for example, researchers at Emory University School of Medicine in Atlanta found that white cell filtration greatly improved surgical outcomes.

Inquiries are increasing

"The results of our study demonstrate we can provide the majority of patients who undergo open-heart surgery an added level of protection," explains John Parker Gott, MD, associate professor of surgery at Emory’s Crawford Long Hospital, who presented his results at a recent meeting of the Southern Thoracic Surgical Association in Atlanta.

"With leukocyte filtration," he says, "we can improve patient outcome significantly and cost-effectively, making this important life-saving procedure even better."

Although cardiac surgeons have known for some time that white blood cells cause tissue injury, use of filtration to reduce the number of white blood cells has not yet become com-mon practice nationwide because no studies have demonstrated clinically that white cell reduction through filtration was effective, Allen says.

"Now that we have clinical studies that demonstrate the benefits of white cell filtration, I’m getting a lot of inquiries from other surgeons, and we should see the practice become more prevalent."

References

1. Allen BS, Rahman S, Ilbawi MN, et al. Detrimental effects of cardiopulmonary bypass in cyanotic infants: Preventing the reoxygenation injury. Ann Thorac Surg 1997; 64:1,381-1,388.

2. Bolling KS, Halldorsson A, Allen BS, et al. Prevention of the hypoxic reoxygenation injury with the use of a leukocyte-depleting filter. J Thorac Cardiovasc Surg 1997; 113:1,081-1,090.