LOS ANGELES — Three years after the U.S. blood banking industry recommended against transfusing plasma from female donors because of a potentially life-threatening antibody reaction, researchers have found that plasma from women may actually be better, not worse, for heart surgery patients. In a study of patients treated before the new guidelines were implemented, those receiving plasma from women were only half as likely to suffer lung complications from the surgery and were 45 percent less likely to be hospitalized or die in the 10 days after surgery, a Duke University Medical Center team reported. The long-term survival rates, however, were the same whether plasma came from men or women. The findings, published in the Journal of Thoracic and Cardiovascular Surgery, were a surprise to the researchers. They had expected that their results would support the informal restrictions on plasma use, said co-author Dr. Nicholas Bandarenko, medical director of Duke Transfusion Services. The findings suggest that, in an effort to minimize the risk of catastrophic lung injury, surgeons may be shifting to problems that are not as serious, but substantially more common. The concern about plasma from women arises from a rare phenomenon known as transfusion-related acute lung injury, commonly known as TRALI. With symptoms very similar to acute respiratory distress syndrome, TRALI affects as many as one in every 3,000 patients who receive a plasma transfusion, killing an estimated 200 people in the United States each year. It is responsible for about half of all transfusion-related deaths. TRALI usually occurs within six hours of a transfusion and is characterized by a sharp buildup of fluids in the lung and other problems. It is thought to be caused by certain antibodies in the plasma that react with immune cells of the body into which they are transfused. Such antibodies are more common in the blood of women because of their pregnancies. In 2006, AABB (formerly the American Association of Blood Banks) recommended that its members take steps to minimize the risk of TRALI. Some institutions, such as the American Red Cross, now use only plasma from men for transfusions, saving that from women for the preparation of drugs and other purposes. Others reject only plasma from women who have had one or more pregnancies. A few hospitals screen all plasma for the antibodies. The concerns do not involve whole blood, and AABB and other organizations emphasize that female blood donors continue to play an important role in maintaining the blood supply. In the study, Dr. Mark Stafford-Smith, an anesthesiology professor at Duke, and his colleagues examined records from 2,157 heart surgery patients at Duke who had received plasma between June 1, 1995, and June 30, 2002. The team identified 309 matched pairs of patients who had received plasma exclusively from either males or females. They found that patients who received plasma exclusively from females had a 5.9 percent incidence of lung problems, compared with 10.8 percent for those who received plasma exclusively from males. The risk of death or hospitalization for the two groups were 9 percent and 16.4 percent, respectively. The findings suggest that there is a variety of potential injuries associated with plasma use following surgery, Bandarenko said, and that they are not likely to be eradicated by policies restricting plasma donation to males only.