Women die and get infections more often than men after heart surgery because they tend to receive more blood transfusions, which boost the risks of bad outcomes, according to a study published in the December Journal of Women's Health.
Co-authored by researchers from the University of Rochester Medical Center and University of Michigan Health System, the study raises another red flag about transfusions, an ancient medical practice that some doctors now believe is overused.
Blood transfusions were once reserved for only the sickest patients, but have evolved from a life-saving therapy to an elective treatment for many illnesses. Patients today receive donor blood, for example, to prevent severe anemia and improve oxygen delivery due to heart failure.
"For 100 years we've assumed blood transfusions are good for people, but most of these clinical practices grew before we had the research to support it," said co-author Neil Blumberg, M.D., professor of Pathology and Laboratory Medicine and director of Transfusion Medicine at the University of Rochester Medical Center.
In the current study, Blumberg and corresponding author Mary Rogers, Ph.D., of the University of Michigan, Department of Internal Medicine, analyzed the data of 380 adult Rochester, N.Y., patients who had primary coronary artery bypass graft surgery, primary valve replacement, or both, in 1997 or 1998 at Strong Memorial Hospital. Researchers looked at in-hospital deaths, lengths of stay, number of days of infection and fever, and whether any patients developed pulmonary dysfunction, a serious side effect of heart surgery. No external funding was received for the study.
Sixty percent of the patients were men and about 40 percent were women. However, the women were 44.6 percent more likely to receive a blood transfusion than the men. Of the 150 women studied, 149 (99 percent) received donor blood during their hospitalization, compared to 77 percent of the men.
Reasons for the gender gap are unclear. Doctors typically measure a patient's hematocrit value, or red blood cell count, before ordering a blood transfusion. Women tend to have lower concentrations of red blood cells than men throughout their lives, Blumberg said. This does not always warrant a transfusion, as the red cell concentration alone does not determine the likelihood of complications from anemia. The study showed that when men and women had equivalent, normal preoperative red blood counts, 99 percent of the women still received transfusions, compared to 62 percent of the men. This suggests a reliance on the red cell concentration as the prime factor in determining when a transfusion is given, the authors said.
Although a direct connection between blood transfusions and infections is being debated among scientists, several studies support the notion that donor blood can provoke a negative response from the patient's immune system.
Of the 380 patients, 13 died while in the hospital; all of the 13 patients received blood transfusions, and infection was strongly related to death. Blood transfusions correlated with more days of fever, more days in intensive care, and a longer hospital stay, particularly if the patient got more than four units of blood. Women were more likely to die in the hospital (6.7 percent) than men (1.3 percent), and 11 percent of the women in the study developed pulmonary dysfunction after surgery, compared with 3.9 percent of the men.
Blood transfusions are very common. The study reports that 41 percent to 71 percent of all Americans have a blood transfusion within their lifetimes. For the year 2003 (the most recent year data was available) a transfusion was the most common procedure performed in U.S. hospitals, according to the Healthcare Cost and Utilization Project (HCUP), a government/industry database widely used by scientists.
Judgments among doctors and hospital transfusion policies can vary greatly across the country. Blumberg and colleagues advocate using donor blood from which the white cells have been removed. This process, called leukoreduction, is believed to diminish the chances of an inflammatory response or infection. (Pall Biomedical, which manufactures leukoreduction filters, has paid lecture fees and awarded other research grants to Blumberg.)
In 1998 the University of Rochester's Strong Memorial Hospital was among the first hospitals in the country to begin using leukoreduced blood for cardiac surgery cases. In 2000, the hospital extended its leukoreduction practice to all other patients.
Additional co-authors are: George L. Hicks, M.D., professor and chief, Division of Cardiothoracic Surgery, University of Rochester; and Joanna M. Heal, M.D., associate medical director, American Red Cross Blood Services, NY-Penn Region.