Fresh Blood Isn't Always Best for Little Heart Patients
WEDNESDAY, Oct. 13 (HealthDayNews) -- Many heart surgeons insist on using fresh, recently donated whole blood when performing open heart surgery on infants, hoping to reduce the risk of complications from the procedure.
However, a new study calls this practice into question.
The research, appearing in the Oct. 14 issue of the New England Journal of Medicine, found that infants who were placed on a heart-lung bypass machine during open heart surgery fared better if the machine was primed with reconstituted blood rather than fresh, whole blood.
"Some surgeons felt that fresh, whole blood was superior to the use of stored blood products, so we did a prospective, randomized trial, and our hypothesis was that fresh, whole blood would confer an advantage," said study author Dr. Steven Mou.
Surprisingly, though, that hypothesis didn't pan out, added Mou, an assistant professor of anesthesiology and pediatric and critical care medicine at Wake Forest University Baptist Medical Center in North Carolina.
Instead, "children who got reconstituted blood actually did better in terms of ICU [intensive-care unit] length of stay. And in the development of post-operative fluid retention, they retained less fluid," he said.
Heart-lung bypass machines temporarily perform the function of the heart during some heart surgeries, adding oxygen to the blood, circulating the blood and keeping it warm.
Fresh, whole blood is blood that has been donated within 48 hours of surgery. According to Mou, fresh blood is often difficult to obtain and is expensive. Reconstituted blood is formed by combining plasma and red blood cells. Red blood cells can be stored for up to 42 days after donation, and plasma can be used for as long as a year after donation, he said.
For the study, 200 infants under 1 year of age who were scheduled to have open heart surgery at Children's Medical Center Dallas were randomly assigned to receive either fresh, whole blood or reconstituted blood in the heart-lung bypass machine. Mou was working at the the University of Texas Southwestern Medical Center at Dallas at the time of the study.
Ninety-six infants were given fresh blood, and 104 received reconstituted blood products to prime the bypass machine.
Mou said priming the bypass machine takes about a unit of blood. A unit of blood is almost equivalent to a pint, or two cups. The average adult body contains about 10 units of blood, according to America's Blood Centers. A newborn's body, by comparison, only contains about one cup -- or roughly half a unit of blood.
Because a baby's body has significantly less blood volume, the fluid used to prime the bypass machine can have a greater impact on infants than it does on adults, explained Mou.
The researchers found that the babies given reconstituted blood stayed in the intensive-care unit for an average of 70.5 hours, compared to 97 hours for the babies given fresh, whole blood. Additionally, the infants on reconstituted blood retained less fluid than those on fresh blood.
Mou said the researchers aren't sure why reconstituted blood appeared to offer benefits over fresh blood. But he speculated that it might be because reconstituted blood doesn't contain platelets, which are important in blood clotting. Or it could be the preservatives in reconstituted blood contain antioxidants, which may confer potential benefits, he said.
The bottom line, said Mou, is that "the use of fresh, whole blood is not superior and its usage should be abandoned."
Dr. L. Henry Edmunds Jr., the Julian Johnson professor of cardiothoracic surgery at the University of Pennsylvania, wrote an accompanying editorial in the journal. He explained that one of the biggest problems in bypassing the heart is that blood begins to clot as soon as it encounters the bypass machine because it's not human tissue. Use of the anticoagulant medication heparin helps to combat this problem.
But, Edmunds said, there's room for much improvement. If researchers could come up with a way to line bypass machines or other artificial organs with endothelial tissue, or find ways to better control the reaction of the blood to the artificial surface, "the payoff would be substantial," he said.
Edmunds said the current study, though not dramatic, is important because it offers an incremental improvement.
"Heart surgery is a lot safer today than it was long ago because of incremental improvements over time," he said.
To learn more about pediatric heart defects and the surgical techniques to correct them, visit the National Library of Medicine.