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Certain Blood Transfusions Increase Risk of Infection

The risk of infection in coronary artery bypass surgery doubles if doctors give the patient a transfusion of blood from another person, according to a study led by epidemiologist Mary Rogers.

"There continued to be considerable variation across hospitals in the use of transfusions," Rogers says. This inconsistency concerns her, she adds, because "we found that [a transfusion of] allogeneic blood, which is blood from a person that is genetically dissimilar from yourself, yielded increased odds of in-hospital infection about twofold."

The body's system-wide response

Rogers says her analysis of nearly 25,000 Medicare patients in Michigan showed that the allogeneic transfusion recipients were at greater risk for a wide range of infections.

"It increased the risk of infection at multiple sites, it wasn't just at the site where the incision was made, but it was increased risk of urinary tract infections, increased risk of respiratory tract infections, blood stream infection, skin infection," Rogers explains. "It was system wide."

Transfusions of the patient's own blood did not appear to have much effect. The University of Michigan researcher suggests the body's reaction to foreign tissue may explain the difference. "There is an immune response to the receipt of this genetically dissimilar tissue and thus people are - their immune system is a bit suppressed, at least temporarily, which puts them at risk of various types of infections."

Rogers stresses, "We don't think it's because of inadvertent contamination of the blood."

Implications for hospital practice

Rogers says this research suggests that hospitals should adopt certain practices to regulate transfusions and make them less common. "Some hospitals have [transfusion] coordinators. Some hospitals have offered bloodless surgery, which means that they try to minimize the use of allogeneic blood for certain procedures if possible."

According to Rogers, several studies currently underway, in which patients are randomly assigned to different treatment groups, should provide more conclusive evidence. Her study is published in the online journal, BMC Medicine.