Commonly, patients are given a transfusion if their hemoglobin level is at or below 10 g/dL, although a growing number of physicians follow a preventive approach using a lower threshold or symptoms of anemia.

A new study comparing two plans for giving blood transfusions following surgery showed no ill effects from postponing transfusion until patients develop signs of anemia or their hemoglobin concentration falls below 8 g/dL. Doctors at the University of Medicine and Dentistry of New Jersey (Newark, NJ, USA) collaborating with other universities, followed 2,016 patients aged 50 years or older with a history of or risk factors for cardiovascular disease, who underwent surgery for hip fracture. Those enrolled were patients at 47 clinical sites in the US and Canada from July 19, 2004, through February 28, 2009. Telephone follow-up ended on May 4, 2009.

The patients were randomized into two groups: one that received a transfusion when their hemoglobin level fell below 10 g/dL (liberal group) and another that received a transfusion when they had symptoms of anemia, or at a physician's discretion if their hemoglobin was below 8 g/dL (restrictive group). The two groups had similar results for a large array of clinical outcomes, including risk for death within 60 days; functional recovery; risk for heart attack, infection, and falls; and symptoms such as fatigue. The difference in blood use was striking. Patients in the restrictive group received 65% fewer units of blood than the liberal group, and 58.5% of patients in the restrictive group did not receive any blood transfusion.

In the US, 14.6 million units of blood are transfused each year. Between 60% and 70% of blood transfusions are given to patients undergoing surgery and the majority of blood transfusions are given to older patients. William Macaulay, MD, coauthor of the study said, "The implications are enormous. Reducing the number of blood transfusions will greatly decrease blood use, potentially saving an enormous amount of money. As the medical community further embraces a restrictive approach to post-surgery blood transfusion, it's important that physicians carefully evaluate patients for symptoms of anemia, and not just rely on hemoglobin levels. The patient's body will often tell us when it needs blood." The study was published on December 14 2011, in the New England Journal of Medicine (NEJM).

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